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packet-x11.c

/* packet-x11.c
 * Routines for X11 dissection
 * Copyright 2000, Christophe Tronche <ch.tronche@computer.org>
 * Copyright 2003, Michael Shuldman
 *
 * $Id: packet-x11.c 13243 2005-02-02 20:07:03Z etxrab $
 *
 * Ethereal - Network traffic analyzer
 * By Gerald Combs <gerald@ethereal.com>
 * Copyright 1998 Gerald Combs
 *
 * Copied from README.developer
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

/* TODO (in no particular order):
 *
 * - keep track of Atom creation by server to be able to display
 *   non-predefined atoms
 * - Idem for keysym <-> keycode ???
 * - Idem for fonts
 * - Subtree the request ids (that is x11.create-window.window and
 *   x11.change-window.window should be  distinct), and add hidden fields
 *   (so we still have x11.window).
 * - add hidden fields so we can have x11.circulate-window in addition to
 *   x11.opcode == 13 (but you could match on x11.opcode == "CirculateWindow"
 *   now)
 * - add hidden fields so we have x11.listOfStuff.length
 * - use a faster scheme that linear list searching for the opcode.
 * - correct display of Unicode chars.
 * - Not everything is homogeneous, in particular the handling of items in
 *   list is a total mess.
 */

/* By the way, I wrote a program to generate every request and test
 * that stuff. If you're interested, you can get it at
 * http://tronche.com/gui/x/
 */

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <assert.h>
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>

#include <string.h>
#include <glib.h>
#include <epan/packet.h>
#include <epan/conversation.h>

#include <epan/prefs.h>
#include "packet-frame.h"
#include "packet-x11-keysymdef.h"

#define cVALS(x) (const value_string*)(x)

/*
 * Data structure associated with a conversation; keeps track of the
 * request for which we're expecting a reply, the frame number of
 * the initial connection request, and the byte order of the connection.
 *
 * An opcode of -3 means we haven't yet seen any requests yet.
 * An opcode of -2 means we're not expecting a reply (unused).
 * An opcode of -1 means we're waiting for a reply to the initial
 * connection request.
 * An opcode of 0  means the request was not seen (or unknown).
 * Other values are the opcode of the request for which we're expecting
 * a reply.
 *
 */
#define NOTHING_SEEN          -3
#define NOTHING_EXPECTED      -2
#define INITIAL_CONN          -1
#define UNKNOWN_OPCODE           0

#define MAX_OPCODES           (255 + 1) /* 255 + INITIAL_CONN */

#define BYTE_ORDER_BE         0
#define BYTE_ORDER_LE         1
#define BYTE_ORDER_UNKNOWN    -1

static const char *modifiers[] = {
    "Shift",
    "Lock",
    "Control",
    "Mod1",
    "Mod2",
    "Mod3",
    "Mod4",
    "Mod5"
};

/* Keymasks.  From <X11/X.h>. */
#define ShiftMask       (1<<0)
#define LockMask        (1<<1)
#define ControlMask           (1<<2)
#define Mod1Mask        (1<<3)
#define Mod2Mask        (1<<4)
#define Mod3Mask        (1<<5)
#define Mod4Mask        (1<<6)
#define Mod5Mask        (1<<7)

static const int modifiermask[] = { ShiftMask, LockMask, ControlMask,
Mod1Mask, Mod2Mask, Mod3Mask, Mod4Mask, Mod5Mask };

/* from <X11/X.h> */
#define NoSymbol             0L /* special KeySym */

typedef struct {
      GHashTable *seqtable;   /* hashtable of sequencenumber <-> opcode. */
      GHashTable *valtable;/* hashtable of sequencenumber <-> &opcode_vals */
      /* major opcodes including extensions (NULL terminated) */
      value_string opcode_vals[MAX_OPCODES+1]; 
      int   sequencenumber;   /* sequencenumber of current packet.         */
      guint32     iconn_frame;      /* frame # of initial connection request   */
      guint32     iconn_reply;      /* frame # of initial connection reply     */
      int   byte_order; /* byte order of connection */
      gboolean  resync;  /* resynchronization of sequence number performed */

      int   *keycodemap[256]; /* keycode to keysymvalue map. */
      int   keysyms_per_keycode;
      int   first_keycode;
      int   *modifiermap[array_length(modifiers)];/* modifier to keycode.*/
      int   keycodes_per_modifier;

      union {
      struct {
            int   first_keycode;
      } GetKeyboardMapping;
      } request;
} x11_conv_data_t;

static GMemChunk *x11_state_chunk = NULL;


/* Initialize the protocol and registered fields */
static int proto_x11 = -1;

#include "x11-declarations.h"

/* Initialize the subtree pointers */
static gint ett_x11 = -1;
static gint ett_x11_color_flags = -1;
static gint ett_x11_list_of_arc = -1;
static gint ett_x11_arc = -1;
static gint ett_x11_list_of_atom = -1;
static gint ett_x11_list_of_card32 = -1;
static gint ett_x11_list_of_color_item = -1;
static gint ett_x11_color_item = -1;
static gint ett_x11_list_of_keycode = -1;
static gint ett_x11_list_of_keysyms = -1;
static gint ett_x11_keysym = -1;
static gint ett_x11_list_of_point = -1;
static gint ett_x11_point = -1;
static gint ett_x11_list_of_rectangle = -1;
static gint ett_x11_rectangle = -1;
static gint ett_x11_list_of_segment = -1;
static gint ett_x11_segment = -1;
static gint ett_x11_list_of_string8 = -1;
static gint ett_x11_list_of_text_item = -1;
static gint ett_x11_text_item = -1;
static gint ett_x11_gc_value_mask = -1;         /* XXX - unused */
static gint ett_x11_event_mask = -1;            /* XXX - unused */
static gint ett_x11_do_not_propagate_mask = -1; /* XXX - unused */
static gint ett_x11_set_of_key_mask = -1;
static gint ett_x11_pointer_event_mask = -1;    /* XXX - unused */
static gint ett_x11_window_value_mask = -1;     /* XXX - unused */
static gint ett_x11_configure_window_mask = -1; /* XXX - unused */
static gint ett_x11_keyboard_value_mask = -1;   /* XXX - unused */
static gint ett_x11_same_screen_focus = -1;

/* desegmentation of X11 messages */
static gboolean x11_desegment = TRUE;

static dissector_handle_t data_handle;

#define TCP_PORT_X11                6000
#define TCP_PORT_X11_2              6001
#define TCP_PORT_X11_3              6002

/*
 * Round a length to a multiple of 4 bytes.
 */
#define ROUND_LENGTH(n) ((((n) + 3)/4) * 4)

/************************************************************************
 ***                                                                  ***
 ***         E N U M   T A B L E S   D E F I N I T I O N S            ***
 ***                                                                  ***
 ************************************************************************/

static const value_string byte_order_vals[] = {
     { 'B', "Big-endian" },
     { 'l', "Little-endian" },
     { 0,   NULL }
};

static const value_string image_byte_order_vals[] = {
     { 0, "LSBFirst" },
     { 1, "MSBFirst" },
     { 0,   NULL }
};

static const value_string access_mode_vals[] = {
      { 0, "Disable" },
      { 1, "Enable" },
      { 0, NULL }
};

static const value_string all_temporary_vals[] = {
      { 0, "AllTemporary" },
      { 0, NULL }
};

static const value_string alloc_vals[] = {
      { 0, "None" },
      { 1, "All" },
      { 0, NULL }
};

static const value_string allow_events_mode_vals[] = {
      { 0, "AsyncPointer" },
      { 1, "SyncPointer" },
      { 2, "ReplayPointer" },
      { 3, "AsyncKeyboard" },
      { 4, "SyncKeyboard" },
      { 5, "ReplayKeyboard" },
      { 6, "AsyncBoth" },
      { 7, "SyncBoth" },
      { 0, NULL }
};

static const value_string arc_mode_vals[] = {
      { 0, "Chord" },
      { 1, "PieSlice" },
      { 0, NULL }
};

static const char *atom_predefined_interpretation[] = {
      "<error>",
      "PRIMARY",
      "SECONDARY",
      "ARC",
      "ATOM",
      "BITMAP",
      "CARDINAL",
      "COLORMAP",
      "CURSOR",
      "CUT_BUFFER0",
      "CUT_BUFFER1",
      "CUT_BUFFER2",
      "CUT_BUFFER3",
      "CUT_BUFFER4",
      "CUT_BUFFER5",
      "CUT_BUFFER6",
      "CUT_BUFFER7",
      "DRAWABLE",
      "FONT",
      "INTEGER",
      "PIXMAP",
      "POINT",
      "RECTANGLE",
      "RESOURCE_MANAGER",
      "RGB_COLOR_MAP",
      "RGB_BEST_MAP",
      "RGB_BLUE_MAP",
      "RGB_DEFAULT_MAP",
      "RGB_GRAY_MAP",
      "RGB_GREEN_MAP",
      "RGB_RED_MAP",
      "STRING",
      "VISUALID",
      "WINDOW",
      "WM_COMMAND",
      "WM_HINTS",
      "WM_CLIENT_MACHINE",
      "WM_ICON_NAME",
      "WM_ICON_SIZE",
      "WM_NAME",
      "WM_NORMAL_HINTS",
      "WM_SIZE_HINTS",
      "WM_ZOOM_HINTS",
      "MIN_SPACE",
      "NORM_SPACE",
      "MAX_SPACE",
      "END_SPACE",
      "SUPERSCRIPT_X",
      "SUPERSCRIPT_Y",
      "SUBSCRIPT_X",
      "SUBSCRIPT_Y",
      "UNDERLINE_POSITION",
      "UNDERLINE_THICKNESS",
      "STRIKEOUT_ASCENT",
      "STRIKEOUT_DESCENT",
      "ITALIC_ANGLE",
      "X_HEIGHT",
      "QUAD_WIDTH",
      "WEIGHT",
      "POINT_SIZE",
      "RESOLUTION",
      "COPYRIGHT",
      "NOTICE",
      "FONT_NAME",
      "FAMILY_NAME",
      "FULL_NAME",
      "CAP_HEIGHT",
      "WM_CLASS",
      "WM_TRANSIENT_FOR",
};

static const value_string auto_repeat_mode_vals[] = {
      { 0, "Off" },
      { 1, "On" },
      { 2, "Default" },
      { 0, NULL }
};

static const value_string background_pixmap_vals[] = {
      { 0, "None" },
      { 1, "ParentRelative" },
      { 0, NULL }
};

static const value_string backing_store_vals[] = {
      { 0, "NotUseful" },
      { 1, "WhenMapped" },
      { 2, "Always" },
      { 0, NULL }
};

static const value_string border_pixmap_vals[] = {
      { 0, "CopyFromParent" },
      { 0, NULL }
};

static const value_string button_vals[] = {
      { 0x8000, "AnyButton" },
      { 0, NULL }
};

static const value_string cap_style_vals[] = {
      { 0, "NotLast" },
      { 1, "Butt" },
      { 2, "Round" },
      { 3, "Projecting" },
      { 0, NULL }
};

static const value_string class_vals[] = {
      { 0, "Cursor" },
      { 1, "Tile" },
      { 2, "Stipple" },
      { 0, NULL }
};

static const value_string close_down_mode_vals[] = {
      { 0, "Destroy" },
      { 1, "RetainPermanent" },
      { 2, "RetainTemporary" },
      { 0, NULL }
};

static const value_string colormap_state_vals[] = {
      { 0, "Uninstalled" },
      { 1, "Installed" },
      { 0, NULL }
};

static const value_string coordinate_mode_vals[] = {
      { 0, "Origin" },
      { 1, "Previous" },
      { 0, NULL }
};

static const value_string destination_vals[] = {
      { 0, "PointerWindow" },
      { 1, "InputFocus" },
      { 0, NULL }
};

static const value_string direction_vals[] = {
      { 0, "RaiseLowest" },
      { 1, "LowerHighest" },
      { 0, NULL }
};

static const value_string event_detail_vals[] = {
      { 0, "Ancestor" },
      { 1, "Virtual" },
      { 2, "Inferior" },
      { 3, "Nonlinear" },
      { 4, "NonlinearVirtual" },
      { 0, NULL }
};

#define FAMILY_INTERNET 0
#define FAMILY_DECNET   1
#define FAMILY_CHAOS    2

static const value_string family_vals[] = {
      { FAMILY_INTERNET, "Internet" },
      { FAMILY_DECNET,   "DECnet" },
      { FAMILY_CHAOS,    "Chaos" },
      { 0, NULL }
};

static const value_string fill_rule_vals[] = {
      { 0, "EvenOdd" },
      { 1, "Winding" },
      { 0, NULL }
};

static const value_string fill_style_vals[] = {
      { 0, "Solid" },
      { 1, "Tiled" },
      { 2, "Stippled" },
      { 3, "OpaqueStippled" },
      { 0, NULL }
};

static const value_string focus_detail_vals[] = {
      { 0, "Ancestor" },
      { 1, "Virtual" },
      { 2, "Inferior" },
      { 3, "Nonlinear" },
      { 4, "NonlinearVirtual" },
      { 5, "Pointer" },
      { 6, "PointerRoot" },
      { 7, "None" },
      { 0, NULL }
};

static const value_string focus_mode_vals[] = {
      {  0, "Normal" },
      {  1, "Grab" },
      {  2, "Ungrab" },
      {  3, "WhileGrabbed" },
      {  0, NULL }
};

static const value_string focus_vals[] = {
      { 0, "None" },
      { 1, "PointerRoot" },
      { 0, NULL }
};

static const value_string function_vals[] = {
      {  0, "Clear" },
      {  1, "And" },
      {  2, "AndReverse" },
      {  3, "Copy" },
      {  4, "AndInverted" },
      {  5, "NoOp" },
      {  6, "Xor" },
      {  7, "Or" },
      {  8, "Nor" },
      {  9, "Equiv" },
      { 10, "Invert" },
      { 11, "OrReverse" },
      { 12, "CopyInverted" },
      { 13, "OrInverted" },
      { 14, "Nand" },
      { 15, "Set" },
      {  0, NULL }
};

static const value_string grab_mode_vals[] = {
      {  0, "Normal" },
      {  1, "Grab" },
      {  2, "Ungrab" },
      {  0, NULL }
};

static const value_string grab_status_vals[] = {
      {  0, "Success" },
      {  1, "AlreadyGrabbed" },
      {  2, "InvalidTime" },
      {  3, "NotViewable" },
      {  4, "Frozen" },
      {  0, NULL }
};

static const value_string gravity_vals[] = {
      {  1, "NorthWest" },
      {  2, "North" },
      {  3, "NorthEast" },
      {  4, "West" },
      {  5, "Center" },
      {  6, "East" },
      {  7, "SouthWest" },
      {  8, "South" },
      {  9, "SouthEast" },
      { 10, "Static" },
      {  0, NULL }
};

static const value_string image_format_vals[] = {
      { 0, "Bitmap" },
      { 1, "XYPixmap" },
      { 2, "ZPixmap" },
      { 0, NULL }
};

static const value_string image_pixmap_format_vals[] = {
      { 1, "XYPixmap" },
      { 2, "ZPixmap" },
      { 0, NULL }
};

static const value_string join_style_vals[] = {
      { 0, "Miter" },
      { 1, "Round" },
      { 2, "Bevel" },
      { 0, NULL }
};

static const value_string key_vals[] = {
      { 0, "AnyKey" },
      { 0, NULL }
};

#include "packet-x11-keysym.h"

static const value_string line_style_vals[] = {
      { 0, "Solid" },
      { 1, "OnOffDash" },
      { 2, "DoubleDash" },
      { 0, NULL }
};

static const value_string mode_vals[] = {
      { 0, "Replace" },
      { 1, "Prepend" },
      { 2, "Append" },
      { 0, NULL }
};

static const value_string on_off_vals[] = {
      { 0, "Off" },
      { 1, "On" },
      { 0, NULL }
};

static const value_string place_vals[] = {
      { 0, "Top" },
      { 1, "Bottom" },
      { 0, NULL }
};

static const value_string property_state_vals[] = {
      { 0, "NewValue" },
      { 1, "Deleted" },
      { 0, NULL }
};

static const value_string visibility_state_vals[] = {
      { 0, "Unobscured" },
      { 1, "PartiallyObscured" },
      { 2, "FullyObscured" },
      { 0, NULL }
};

/* Requestcodes.  From <X11/Xproto.h>. */
#define X_CreateWindow                  1              
#define X_ChangeWindowAttributes        2        
#define X_GetWindowAttributes           3     
#define X_DestroyWindow                 4
#define X_DestroySubwindows             5   
#define X_ChangeSaveSet                 6
#define X_ReparentWindow                7
#define X_MapWindow                     8
#define X_MapSubwindows                 9
#define X_UnmapWindow                  10
#define X_UnmapSubwindows              11  
#define X_ConfigureWindow              12  
#define X_CirculateWindow              13  
#define X_GetGeometry                  14
#define X_QueryTree                    15
#define X_InternAtom                   16
#define X_GetAtomName                  17
#define X_ChangeProperty               18 
#define X_DeleteProperty               19 
#define X_GetProperty                  20
#define X_ListProperties               21 
#define X_SetSelectionOwner            22    
#define X_GetSelectionOwner            23    
#define X_ConvertSelection             24   
#define X_SendEvent                    25
#define X_GrabPointer                  26
#define X_UngrabPointer                27
#define X_GrabButton                   28
#define X_UngrabButton                 29
#define X_ChangeActivePointerGrab      30          
#define X_GrabKeyboard                 31
#define X_UngrabKeyboard               32 
#define X_GrabKey                      33
#define X_UngrabKey                    34
#define X_AllowEvents                  35       
#define X_GrabServer                   36      
#define X_UngrabServer                 37        
#define X_QueryPointer                 38        
#define X_GetMotionEvents              39           
#define X_TranslateCoords              40                
#define X_WarpPointer                  41       
#define X_SetInputFocus                42         
#define X_GetInputFocus                43         
#define X_QueryKeymap                  44       
#define X_OpenFont                     45    
#define X_CloseFont                    46     
#define X_QueryFont                    47
#define X_QueryTextExtents             48     
#define X_ListFonts                    49  
#define X_ListFontsWithInfo            50 
#define X_SetFontPath                  51 
#define X_GetFontPath                  52 
#define X_CreatePixmap                 53        
#define X_FreePixmap                   54      
#define X_CreateGC                     55    
#define X_ChangeGC                     56    
#define X_CopyGC                       57  
#define X_SetDashes                    58     
#define X_SetClipRectangles            59             
#define X_FreeGC                       60  
#define X_ClearArea                    61             
#define X_CopyArea                     62    
#define X_CopyPlane                    63     
#define X_PolyPoint                    64     
#define X_PolyLine                     65    
#define X_PolySegment                  66       
#define X_PolyRectangle                67         
#define X_PolyArc                      68   
#define X_FillPoly                     69    
#define X_PolyFillRectangle            70             
#define X_PolyFillArc                  71       
#define X_PutImage                     72    
#define X_GetImage                     73 
#define X_PolyText8                    74     
#define X_PolyText16                   75      
#define X_ImageText8                   76      
#define X_ImageText16                  77       
#define X_CreateColormap               78          
#define X_FreeColormap                 79        
#define X_CopyColormapAndFree          80               
#define X_InstallColormap              81           
#define X_UninstallColormap            82             
#define X_ListInstalledColormaps       83                  
#define X_AllocColor                   84      
#define X_AllocNamedColor              85           
#define X_AllocColorCells              86           
#define X_AllocColorPlanes             87            
#define X_FreeColors                   88      
#define X_StoreColors                  89       
#define X_StoreNamedColor              90           
#define X_QueryColors                  91       
#define X_LookupColor                  92       
#define X_CreateCursor                 93        
#define X_CreateGlyphCursor            94             
#define X_FreeCursor                   95      
#define X_RecolorCursor                96         
#define X_QueryBestSize                97         
#define X_QueryExtension               98          
#define X_ListExtensions               99          
#define X_ChangeKeyboardMapping        100
#define X_GetKeyboardMapping           101
#define X_ChangeKeyboardControl        102                
#define X_GetKeyboardControl           103             
#define X_Bell                         104
#define X_ChangePointerControl         105
#define X_GetPointerControl            106
#define X_SetScreenSaver               107          
#define X_GetScreenSaver               108          
#define X_ChangeHosts                  109       
#define X_ListHosts                    110     
#define X_SetAccessControl             111               
#define X_SetCloseDownMode             112
#define X_KillClient                   113 
#define X_RotateProperties             114
#define X_ForceScreenSaver             115
#define X_SetPointerMapping            116
#define X_GetPointerMapping            117
#define X_SetModifierMapping           118
#define X_GetModifierMapping           119
#define X_NoOperation                  127
#define X_FirstExtension                   128
#define X_LastExtension              255

static const value_string opcode_vals[] = {
      { INITIAL_CONN,                   "Initial connection request" },
      { X_CreateWindow,                 "CreateWindow" },
      { X_ChangeWindowAttributes,       "ChangeWindowAttributes" },
      { X_GetWindowAttributes,          "GetWindowAttributes" },
      { X_DestroyWindow,                "DestroyWindow" },
      { X_DestroySubwindows,            "DestroySubwindows" },
      { X_ChangeSaveSet,                "ChangeSaveSet" },
      { X_ReparentWindow,               "ReparentWindow" },
      { X_MapWindow,                    "MapWindow" },
      { X_MapSubwindows,                "MapSubwindows" },
      { X_UnmapWindow,                  "UnmapWindow" },
      { X_UnmapSubwindows,              "UnmapSubwindows" },
      { X_ConfigureWindow,              "ConfigureWindow" },
      { X_CirculateWindow,              "CirculateWindow" },
      { X_GetGeometry,                  "GetGeometry" },
      { X_QueryTree,                    "QueryTree" },
      { X_InternAtom,                   "InternAtom" },
      { X_GetAtomName,                  "GetAtomName" },
      { X_ChangeProperty,               "ChangeProperty" },
      { X_DeleteProperty,               "DeleteProperty" },
      { X_GetProperty,                  "GetProperty" },
      { X_ListProperties,               "ListProperties" },
      { X_SetSelectionOwner,            "SetSelectionOwner" },
      { X_GetSelectionOwner,            "GetSelectionOwner" },
      { X_ConvertSelection,             "ConvertSelection" },
      { X_SendEvent,                    "SendEvent" },
      { X_GrabPointer,                  "GrabPointer" },
      { X_UngrabPointer,                "UngrabPointer" },
      { X_GrabButton,                   "GrabButton" },
      { X_UngrabButton,                 "UngrabButton" },
      { X_ChangeActivePointerGrab,      "ChangeActivePointerGrab" },
      { X_GrabKeyboard,                 "GrabKeyboard" },
      { X_UngrabKeyboard,               "UngrabKeyboard" },
      { X_GrabKey,                      "GrabKey" },
      { X_UngrabKey,                    "UngrabKey" },
      { X_AllowEvents,                  "AllowEvents" },
      { X_GrabServer,                   "GrabServer" },
      { X_UngrabServer,                 "UngrabServer" },
      { X_QueryPointer,                 "QueryPointer" },
      { X_GetMotionEvents,              "GetMotionEvents" },
      { X_TranslateCoords,              "TranslateCoordinates" },
      { X_WarpPointer,                  "WarpPointer" },
      { X_SetInputFocus,                "SetInputFocus" },
      { X_GetInputFocus,                "GetInputFocus" },
      { X_QueryKeymap,                  "QueryKeymap" },
      { X_OpenFont,                     "OpenFont" },
      { X_CloseFont,                    "CloseFont" },
      { X_QueryFont,                    "QueryFont" },
      { X_QueryTextExtents,             "QueryTextExtents" },
      { X_ListFonts,                    "ListFonts" },
      { X_ListFontsWithInfo,            "ListFontsWithInfo" },
      { X_SetFontPath,                  "SetFontPath" },
      { X_GetFontPath,                  "GetFontPath" },
      { X_CreatePixmap,                 "CreatePixmap" },
      { X_FreePixmap,                   "FreePixmap" },
      { X_CreateGC,                     "CreateGC" },
      { X_ChangeGC,                     "ChangeGC" },
      { X_CopyGC,                       "CopyGC" },
      { X_SetDashes,                    "SetDashes" },
      { X_SetClipRectangles,            "SetClipRectangles" },
      { X_FreeGC,                       "FreeGC" },
      { X_ClearArea,                    "ClearArea" },
      { X_CopyArea,                     "CopyArea" },
      { X_CopyPlane,                    "CopyPlane" },
      { X_PolyPoint,                    "PolyPoint" },
      { X_PolyLine,                     "PolyLine" },
      { X_PolySegment,                  "PolySegment" },
      { X_PolyRectangle,                "PolyRectangle" },
      { X_PolyArc,                      "PolyArc" },
      { X_FillPoly,                     "FillPoly" },
      { X_PolyFillRectangle,            "PolyFillRectangle" },
      { X_PolyFillArc,                  "PolyFillArc" },
      { X_PutImage,                     "PutImage" },
      { X_GetImage,                     "GetImage" },
      { X_PolyText8,                    "PolyText8" },
      { X_PolyText16,                   "PolyText16" },
      { X_ImageText8,                   "ImageText8" },
      { X_ImageText16,                  "ImageText16" },
      { X_CreateColormap,               "CreateColormap" },
      { X_FreeColormap,                 "FreeColormap" },
      { X_CopyColormapAndFree,          "CopyColormapAndFree" },
      { X_InstallColormap,              "InstallColormap" },
      { X_UninstallColormap,            "UninstallColormap" },
      { X_ListInstalledColormaps,       "ListInstalledColormaps" },
      { X_AllocColor,                   "AllocColor" },
      { X_AllocNamedColor,              "AllocNamedColor" },
      { X_AllocColorCells,              "AllocColorCells" },
      { X_AllocColorPlanes,             "AllocColorPlanes" },
      { X_FreeColors,                   "FreeColors" },
      { X_StoreColors,                  "StoreColors" },
      { X_StoreNamedColor,              "StoreNamedColor" },
      { X_QueryColors,                  "QueryColors" },
      { X_LookupColor,                  "LookupColor" },
      { X_CreateCursor,                 "CreateCursor" },
      { X_CreateGlyphCursor,            "CreateGlyphCursor" },
      { X_FreeCursor,                   "FreeCursor" },
      { X_RecolorCursor,                "RecolorCursor" },
      { X_QueryBestSize,                "QueryBestSize" },
      { X_QueryExtension,               "QueryExtension" },
      { X_ListExtensions,               "ListExtensions" },
      { X_ChangeKeyboardMapping,        "ChangeKeyboardMapping" },
      { X_GetKeyboardMapping,           "GetKeyboardMapping" },
      { X_ChangeKeyboardControl,        "ChangeKeyboardControl" },
      { X_GetKeyboardControl,           "GetKeyboardControl" },
      { X_Bell,                         "Bell" },
      { X_ChangePointerControl,         "ChangePointerControl" },
      { X_GetPointerControl,            "GetPointerControl" },
      { X_SetScreenSaver,               "SetScreenSaver" },
      { X_GetScreenSaver,               "GetScreenSaver" },
      { X_ChangeHosts,                  "ChangeHosts" },
      { X_ListHosts,                    "ListHosts" },
      { X_SetAccessControl,             "SetAccessControl" },
      { X_SetCloseDownMode,             "SetCloseDownMode" },
      { X_KillClient,                   "KillClient" },
      { X_RotateProperties,             "RotateProperties" },
      { X_ForceScreenSaver,             "ForceScreenSaver" },
      { X_SetPointerMapping,            "SetPointerMapping" },
      { X_GetPointerMapping,            "GetPointerMapping" },
      { X_SetModifierMapping,           "SetModifierMapping" },
      { X_GetModifierMapping,           "GetModifierMapping" },
      { X_NoOperation,                  "NoOperation" },
      { 0,                              NULL }
};

/* Eventscodes.  From <X11/X.h>. */
#define KeyPress        2
#define KeyRelease            3
#define ButtonPress           4
#define ButtonRelease         5
#define MotionNotify          6
#define EnterNotify           7
#define LeaveNotify           8
#define FocusIn               9
#define FocusOut        10
#define KeymapNotify          11
#define Expose                12
#define GraphicsExpose        13
#define NoExpose        14
#define VisibilityNotify      15
#define CreateNotify          16
#define DestroyNotify         17
#define UnmapNotify           18
#define MapNotify       19
#define MapRequest            20
#define ReparentNotify        21
#define ConfigureNotify       22
#define ConfigureRequest      23
#define GravityNotify         24
#define ResizeRequest         25
#define CirculateNotify       26
#define CirculateRequest      27
#define PropertyNotify        28
#define SelectionClear        29
#define SelectionRequest      30
#define SelectionNotify       31
#define ColormapNotify        32
#define ClientMessage         33
#define MappingNotify         34
#define FirstExtensionEvent   64
#define LastExtensionEvent    127

static const value_string eventcode_vals[] = {
      { KeyPress,          "KeyPress" },
      { KeyRelease,        "KeyRelease" },
      { ButtonPress,       "ButtonPress" },
      { ButtonRelease,     "ButtonRelease" },
      { MotionNotify,      "MotionNotify" },
      { EnterNotify,       "EnterNotify" },
      { LeaveNotify,       "LeaveNotify" },
      { FocusIn,           "FocusIn" },
      { FocusOut,          "FocusOut" },
      { KeymapNotify,      "KeymapNotify" },
      { Expose,            "Expose" },
      { GraphicsExpose,    "GraphicsExpose" },
      { NoExpose,          "NoExpose" },
      { VisibilityNotify,  "VisibilityNotify" },
      { CreateNotify,      "CreateNotify" },
      { DestroyNotify,     "DestroyNotify" },
      { UnmapNotify,       "UnmapNotify" },
      { MapNotify,         "MapNotify" },
      { MapRequest,        "MapRequest" },
      { ReparentNotify,    "ReparentNotify" },
      { ConfigureNotify,   "ConfigureNotify" },
      { ConfigureRequest,  "ConfigureRequest" },
      { GravityNotify,     "GravityNotify" },
      { ResizeRequest,     "ResizeRequest" },
      { CirculateNotify,   "CirculateNotify" },
      { CirculateRequest,  "CirculateRequest" },
      { PropertyNotify,    "PropertyNotify" },
      { SelectionClear,    "SelectionClear" },
      { SelectionRequest,  "SelectionRequest" },
      { SelectionNotify,   "SelectionNotify" },
      { ColormapNotify,    "ColormapNotify" },
      { ClientMessage,     "ClientMessage" },
      { MappingNotify,     "MappingNotify" },
      { 0,                 NULL }
};

/* Errorcodes.  From <X11/X.h> */
#define Success               0     /* everything's okay */
#define BadRequest            1     /* bad request code */
#define BadValue        2     /* int parameter out of range */
#define BadWindow       3     /* parameter not a Window */
#define BadPixmap       4     /* parameter not a Pixmap */
#define BadAtom               5     /* parameter not an Atom */
#define BadCursor       6     /* parameter not a Cursor */
#define BadFont               7     /* parameter not a Font */
#define BadMatch        8     /* parameter mismatch */
#define BadDrawable           9     /* parameter not a Pixmap or Window */
#define BadAccess       10    /* depending on context:
                               - key/button already grabbed
                               - attempt to free an illegal 
                                 cmap entry 
                              - attempt to store into a read-only 
                                 color map entry.
                              - attempt to modify the access control
                                 list from other than the local host.
                              */
#define BadAlloc        11    /* insufficient resources */
#define BadColor        12    /* no such colormap */
#define BadGC                 13    /* parameter not a GC */
#define BadIDChoice           14    /* choice not in range or already used */
#define BadName               15    /* font or color name doesn't exist */
#define BadLength       16    /* Request length incorrect */
#define BadImplementation     17    /* server is defective */

#define FirstExtensionError   128
#define LastExtensionError    255

static const value_string errorcode_vals[] = {
      { Success,               "Success" },
      { BadRequest,            "BadRequest" },
      { BadValue,              "BadValue" },
      { BadWindow,             "BadWindow" },
      { BadPixmap,             "BadPixmap" },
      { BadAtom,               "BadAtom" },
      { BadCursor,             "BadCursor" },
      { BadFont,               "BadFont" },
      { BadMatch,              "BadMatch" },
      { BadDrawable,           "BadDrawable" },
      { BadAccess,             "BadAccess" },
      { BadAlloc,              "BadAlloc" },
      { BadColor,              "BadColor" },
      { BadGC,                 "BadGC" },
      { BadIDChoice,           "BadIDChoice" },
      { BadName,               "BadName" },
      { BadLength,             "BadLength" },
      { BadImplementation,     "BadImplementation" },
      { FirstExtensionError,   "FirstExtensionError" },
      { LastExtensionError,    "LastExtensionError" },
      { 0,                     NULL }
};

static const value_string ordering_vals[] = {
      { 0, "UnSorted" },
      { 1, "YSorted" },
      { 2, "YXSorted" },
      { 3, "YXBanded" },
      { 0, NULL }
};

static const value_string plane_mask_vals[] = {
      { 0xFFFFFFFF, "AllPlanes" },
      { 0, NULL }
};

static const value_string pointer_keyboard_mode_vals[] = {
      { 0, "Synchronous" },
      { 1, "Asynchronous" },
      { 0, NULL }
};

static const value_string revert_to_vals[] = {
      { 0, "None" },
      { 1, "PointerRoot" },
      { 2, "Parent" },
      { 0, NULL }
};

static const value_string insert_delete_vals[] = {
      { 0, "Insert" },
      { 1, "Delete" },
      { 0, NULL }
};

static const value_string screen_saver_mode_vals[] = {
      { 0, "Reset" },
      { 1, "Activate" },
      { 0, NULL }
};

static const value_string shape_vals[] = {
      { 0, "Complex" },
      { 1, "Nonconvex" },
      { 2, "Convex" },
      { 0, NULL }
};

static const value_string stack_mode_vals[] = {
      { 0, "Above" },
      { 1, "Below" },
      { 2, "TopIf" },
      { 3, "BottomIf" },
      { 4, "Opposite" },
      { 0, NULL }
};

static const value_string subwindow_mode_vals[] = {
      { 0, "ClipByChildren" },
      { 1, "IncludeInferiors" },
      { 0, NULL }
};

static const value_string window_class_vals[] = {
      { 0, "CopyFromParent" },
      { 1, "InputOutput" },
      { 2, "InputOnly" },
      { 0, NULL }
};

static const value_string yes_no_default_vals[] = {
      { 0, "No" },
      { 1, "Yes" },
      { 2, "Default" },
      { 0, NULL }
};

static const value_string zero_is_any_property_type_vals[] = {
      { 0, "AnyPropertyType" },
      { 0, NULL }
};

static const value_string zero_is_none_vals[] = {
      { 0, "None" },
      { 0, NULL }
};

/* we have not seen packet before. */
#define PACKET_IS_NEW(pinfo) \
      (!((pinfo)->fd->flags.visited))

/************************************************************************
 ***                                                                  ***
 ***           F I E L D   D E C O D I N G   M A C R O S              ***
 ***                                                                  ***
 ************************************************************************/

#define VALUE8(tvb, offset) (tvb_get_guint8(tvb, offset))
#define VALUE16(tvb, offset) (little_endian ? tvb_get_letohs(tvb, offset) : tvb_get_ntohs(tvb, offset))
#define VALUE32(tvb, offset) (little_endian ? tvb_get_letohl(tvb, offset) : tvb_get_ntohl(tvb, offset))

#define FIELD8(name)  (field8(tvb, offsetp, t, hf_x11_##name, little_endian))
#define FIELD16(name) (field16(tvb, offsetp, t, hf_x11_##name, little_endian))
#define FIELD32(name) (field32(tvb, offsetp, t, hf_x11_##name, little_endian))

#define BITFIELD(TYPE, position, name) {\
  int unused;\
  int save = *offsetp;\
  proto_tree_add_item(bitmask_tree, hf_x11_##position##_##name, tvb, bitmask_offset, \
                      bitmask_size, little_endian); \
  if (bitmask_value & proto_registrar_get_nth(hf_x11_##position##_##name) -> bitmask) {\
       TYPE(name);\
       unused = save + 4 - *offsetp;\
       if (unused)\
           proto_tree_add_item(t, hf_x11_unused, tvb, *offsetp, unused, little_endian);\
       *offsetp = save + 4;\
 }\
}

#define FLAG(position, name) {\
       proto_tree_add_boolean(bitmask_tree, hf_x11_##position##_mask##_##name, tvb, bitmask_offset, bitmask_size, bitmask_value); }

#define FLAG_IF_NONZERO(position, name) do {\
  if (bitmask_value & proto_registrar_get_nth(hf_x11_##position##_mask##_##name) -> bitmask)\
       proto_tree_add_boolean(bitmask_tree, hf_x11_##position##_mask##_##name, tvb, bitmask_offset, bitmask_size, bitmask_value); } while (0)

#define ATOM(name)     { atom(tvb, offsetp, t, hf_x11_##name, little_endian); }
#define BITGRAVITY(name) { gravity(tvb, offsetp, t, hf_x11_##name, "Forget"); }
#define BITMASK(name, size) {\
      proto_item *ti; \
      guint32 bitmask_value; \
      int bitmask_offset; \
      int bitmask_size; \
      proto_tree *bitmask_tree; \
      bitmask_value = ((size == 1) ? (guint32)VALUE8(tvb, *offsetp) : \
                   ((size == 2) ? (guint32)VALUE16(tvb, *offsetp) : \
                                (guint32)VALUE32(tvb, *offsetp))); \
      bitmask_offset = *offsetp; \
      bitmask_size = size; \
      ti = proto_tree_add_uint(t, hf_x11_##name##_mask, tvb, *offsetp, size, bitmask_value); \
      bitmask_tree = proto_item_add_subtree(ti, ett_x11_##name##_mask); \
      *offsetp += size;
#define ENDBITMASK      }
#define BITMASK8(name)  BITMASK(name, 1);
#define BITMASK16(name) BITMASK(name, 2);
#define BITMASK32(name) BITMASK(name, 4);
#define BOOL(name)     (add_boolean(tvb, offsetp, t, hf_x11_##name))
#define BUTTON(name)   FIELD8(name)
#define CARD8(name)    FIELD8(name)
#define CARD16(name)   (FIELD16(name))
#define CARD32(name)   (FIELD32(name))
#define COLOR_FLAGS(name) colorFlags(tvb, offsetp, t)
#define COLORMAP(name) FIELD32(name)
#define CURSOR(name)   FIELD32(name)
#define DRAWABLE(name) FIELD32(name)
#define ENUM8(name)    (FIELD8(name))
#define ENUM16(name)   (FIELD16(name))
#define FONT(name)     FIELD32(name)
#define FONTABLE(name) FIELD32(name)
#define GCONTEXT(name) FIELD32(name)
#define INT8(name)     FIELD8(name)
#define INT16(name)    FIELD16(name)
#define INT32(name)    FIELD32(name)
#define KEYCODE(name)  FIELD8(name)
#define KEYCODE_DECODED(name, keycode, mask)  do {                \
      proto_tree_add_uint_format(t, hf_x11_##name, tvb, offset, 1,      \
      keycode, "keycode: %d (%s)",                    \
      keycode,  keycode2keysymString(state->keycodemap,           \
      state->first_keycode, state->keysyms_per_keycode,           \
      state->modifiermap, state->keycodes_per_modifier,           \
      keycode, mask));                                \
      ++offset;                                       \
} while (0)

#define LISTofARC(name) { listOfArc(tvb, offsetp, t, hf_x11_##name, (next_offset - *offsetp) / 12, little_endian); }
#define LISTofATOM(name, length) { listOfAtom(tvb, offsetp, t, hf_x11_##name, (length) / 4, little_endian); }
#define LISTofBYTE(name, length) { listOfByte(tvb, offsetp, t, hf_x11_##name, (length), little_endian); }
#define LISTofCARD8(name, length) { listOfByte(tvb, offsetp, t, hf_x11_##name, (length), little_endian); }
#define LISTofIPADDRESS(name, length) { listOfByte(tvb, offsetp, t, hf_x11_##name, (length), FALSE); }
#define LISTofCARD32(name, length) { listOfCard32(tvb, offsetp, t, hf_x11_##name, hf_x11_##name##_item, (length) / 4, little_endian); }
#define LISTofCOLORITEM(name, length) { listOfColorItem(tvb, offsetp, t, hf_x11_##name, (length) / 12, little_endian); }
#define LISTofKEYCODE(map, name, length) { listOfKeycode(tvb, offsetp, t, hf_x11_##name, map, (length), little_endian); }
#define LISTofKEYSYM(name, map, keycode_first, keycode_count, \
    keysyms_per_keycode) {\
      listOfKeysyms(tvb, offsetp, t, hf_x11_##name, hf_x11_##name##_item, map, (keycode_first), (keycode_count), (keysyms_per_keycode), little_endian); }
#define LISTofPOINT(name, length) { listOfPoint(tvb, offsetp, t, hf_x11_##name, (length) / 4, little_endian); }
#define LISTofRECTANGLE(name) { listOfRectangle(tvb, offsetp, t, hf_x11_##name, (next_offset - *offsetp) / 8, little_endian); }
#define LISTofSEGMENT(name) { listOfSegment(tvb, offsetp, t, hf_x11_##name, (next_offset - *offsetp) / 8, little_endian); }
#define LISTofSTRING8(name, length) { listOfString8(tvb, offsetp, t, hf_x11_##name, hf_x11_##name##_string, (length), little_endian); }
#define LISTofTEXTITEM8(name) { listOfTextItem(tvb, offsetp, t, hf_x11_##name, FALSE, next_offset, little_endian); }
#define LISTofTEXTITEM16(name) { listOfTextItem(tvb, offsetp, t, hf_x11_##name, TRUE, next_offset, little_endian); }
#define OPCODE()       { opcode = FIELD8(opcode); }
#define PIXMAP(name)   { FIELD32(name); }
#define REQUEST_LENGTH() (requestLength(tvb, offsetp, t, little_endian))
#define SETofEVENT(name) { setOfEvent(tvb, offsetp, t, little_endian); }
#define SETofDEVICEEVENT(name) { setOfDeviceEvent(tvb, offsetp, t, little_endian);}
#define SETofKEYMASK(name) { setOfKeyButMask(tvb, offsetp, t, little_endian, 0); }
#define SETofKEYBUTMASK(name) { setOfKeyButMask(tvb, offsetp, t, little_endian, 1); }
#define SETofPOINTEREVENT(name) { setOfPointerEvent(tvb, offsetp, t, little_endian); }
#define STRING8(name, length)  { string8(tvb, offsetp, t, hf_x11_##name, length); }
#define STRING16(name, length)  { string16(tvb, offsetp, t, hf_x11_##name, hf_x11_##name##_bytes, length, little_endian); }
#define TIMESTAMP(name){ timestamp(tvb, offsetp, t, hf_x11_##name, little_endian); }
#define UNDECODED(x)   { proto_tree_add_item(t, hf_x11_undecoded, tvb, *offsetp,  x, little_endian); *offsetp += x; }
#define UNUSED(x)      { proto_tree_add_item(t, hf_x11_unused, tvb, *offsetp,  x, little_endian); *offsetp += x; }
#define PAD()          { if (next_offset - *offsetp > 0) proto_tree_add_item(t, hf_x11_unused, tvb, *offsetp, next_offset - *offsetp, little_endian); *offsetp = next_offset; }
#define WINDOW(name)   { FIELD32(name); }
#define WINGRAVITY(name) { gravity(tvb, offsetp, t, hf_x11_##name, "Unmap"); }

#define VISUALID(name) { gint32 v = VALUE32(tvb, *offsetp); \
    proto_tree_add_uint_format(t, hf_x11_##name, tvb, *offsetp, 4, v, "Visualid: 0x%08x%s", v, \
                         v ? "" : " (CopyFromParent)"); *offsetp += 4; }
#define REPLY(name)       FIELD8(name);
#define REPLYLENGTH(name) FIELD32(name);

#define EVENTCONTENTS_COMMON() do {                                    \
                  TIMESTAMP(time);                         \
                  WINDOW(rootwindow);                            \
                  WINDOW(eventwindow);                           \
                  WINDOW(childwindow);                           \
                  INT16(root_x);                                 \
                  INT16(root_y);                                 \
                  INT16(event_x);                                \
                  INT16(event_y);                                \
                  setOfKeyButMask(tvb, offsetp, t, little_endian, 1);  \
} while (0)

#define SEQUENCENUMBER_REPLY(name) do {                           \
      guint16 seqno;                                                  \
                                                                        \
      seqno = VALUE16(tvb, *offsetp);                                 \
      proto_tree_add_uint_format(t, hf_x11_reply_##name, tvb,         \
      *offsetp, sizeof(seqno), seqno,                                 \
      "sequencenumber: %d (%s)",                                        \
      (int)seqno,                                                     \
      val_to_str(opcode, state->opcode_vals, "<Unknown opcode %d>"));   \
      *offsetp += sizeof(seqno);                                      \
} while (0) 

#define REPLYCONTENTS_COMMON() do {                               \
      REPLY(reply);                                         \
      proto_tree_add_item(t, hf_x11_undecoded, tvb, offset,             \
      1, little_endian);                                    \
      ++offset;                                       \
      SEQUENCENUMBER_REPLY(sequencenumber);                       \
      REPLYLENGTH(replylength);                             \
      proto_tree_add_item(t, hf_x11_undecoded, tvb, offset,             \
      tvb_reported_length_remaining(tvb, offset), little_endian); \
      offset += tvb_reported_length_remaining(tvb, offset);       \
} while (0)


#define HANDLE_REPLY(plen, length_remaining, str, func) do {            \
      if (length_remaining < plen) {                              \
            if (x11_desegment && pinfo->can_desegment) {          \
                  pinfo->desegment_offset = offset;         \
                  pinfo->desegment_len    = plen - length_remaining;\
                  return;                                   \
            } else {                                  \
                  ; /* XXX yes, what then?  Need to skip/join. */ \
            }                                         \
      }                                               \
      if (length_remaining > plen)                          \
            length_remaining = plen;                        \
      next_tvb = tvb_new_subset(tvb, offset, length_remaining, plen);   \
                                                      \
      if (sep == NULL) {                                    \
         if (check_col(pinfo->cinfo, COL_INFO))             \
               col_add_str(pinfo->cinfo, COL_INFO, str);          \
         sep = ":";                                         \
      }                                               \
                                                      \
      TRY {                                           \
            func(next_tvb, pinfo, tree, sep, state, little_endian);     \
      }                                               \
                                                      \
      CATCH(BoundsError) {                                  \
            RETHROW;                                  \
      }                                               \
      CATCH(ReportedBoundsError) {                          \
            show_reported_bounds_error(next_tvb, pinfo, tree);    \
      }                                               \
      ENDTRY;                                               \
                                                      \
      sep = ",";                                      \
} while (0) 

static void
dissect_x11_initial_reply(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
              const char *sep, x11_conv_data_t *volatile state,
              gboolean little_endian);

static void
dissect_x11_reply(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
              const char *volatile sep, x11_conv_data_t *volatile state,
              gboolean little_endian);

static void
dissect_x11_error(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
              const char *volatile sep, x11_conv_data_t *volatile state,
              gboolean little_endian);

static void
dissect_x11_event(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
              const char *volatile sep, x11_conv_data_t *volatile state,
              gboolean little_endian);

static void
x11_stateinit(x11_conv_data_t **state, conversation_t *conversation);

static const char *
keysymString(guint32 v);


/************************************************************************
 ***                                                                  ***
 ***                  D E C O D I N G   F I E L D S                   ***
 ***                                                                  ***
 ************************************************************************/

static void atom(tvbuff_t *tvb, int *offsetp, proto_tree *t, int hf,
             gboolean little_endian)
{
      const char *interpretation = NULL;

      guint32 v = VALUE32(tvb, *offsetp);
      if (v >= 1 && v < array_length(atom_predefined_interpretation))
          interpretation = atom_predefined_interpretation[v];
      else if (v)
          interpretation = "Not a predefined atom";
      else {
          header_field_info *hfi = proto_registrar_get_nth(hf);
          if (hfi -> strings)
              interpretation = match_strval(v, cVALS(hfi -> strings));
      }
      if (!interpretation) interpretation = "error in Xlib client program ?";
      proto_tree_add_uint_format(t, hf, tvb, *offsetp, 4, v, "%s: %u (%s)",
                         proto_registrar_get_nth(hf) -> name, v, interpretation);
      *offsetp += 4;
}

static guint32 add_boolean(tvbuff_t *tvb, int *offsetp, proto_tree *t, int hf)
{
      guint32 v = VALUE8(tvb, *offsetp);
      proto_tree_add_boolean(t, hf, tvb, *offsetp, 1, v);
      *offsetp += 1;
      return v;
}

static void colorFlags(tvbuff_t *tvb, int *offsetp, proto_tree *t)
{
      unsigned do_red_green_blue = VALUE8(tvb, *offsetp);
      proto_item *ti;
      proto_tree *tt;

      if (do_red_green_blue) {
          int sep = FALSE;
          char buffer[512];
          char *bp = buffer + sprintf(buffer, "flags: ");

          if (do_red_green_blue & 0x1) {
              bp += sprintf(bp, "DoRed");
              sep = TRUE;
          }

          if (do_red_green_blue & 0x2) {
              if (sep) bp += sprintf(bp, " | ");
              bp += sprintf(bp, "DoGreen");
              sep = TRUE;
          }

          if (do_red_green_blue & 0x4) {
              if (sep) bp += sprintf(bp, " | ");
              bp += sprintf(bp, "DoBlue");
              sep = TRUE;
          }

          if (do_red_green_blue & 0xf8) {
              if (sep) bp += sprintf(bp, " + ");
              sprintf(bp, "trash");
          }

          ti = proto_tree_add_uint_format(t, hf_x11_coloritem_flags, tvb, *offsetp, 1, do_red_green_blue,
                                  "%s", buffer);
          tt = proto_item_add_subtree(ti, ett_x11_color_flags);
          if (do_red_green_blue & 0x1)
              proto_tree_add_boolean(tt, hf_x11_coloritem_flags_do_red, tvb, *offsetp, 1,
                               do_red_green_blue & 0x1);
          if (do_red_green_blue & 0x2)
              proto_tree_add_boolean(tt, hf_x11_coloritem_flags_do_green, tvb, *offsetp, 1,
                               do_red_green_blue & 0x2);
          if (do_red_green_blue & 0x4)
              proto_tree_add_boolean(tt, hf_x11_coloritem_flags_do_blue, tvb, *offsetp, 1,
                               do_red_green_blue & 0x4);
          if (do_red_green_blue & 0xf8)
              proto_tree_add_boolean(tt, hf_x11_coloritem_flags_unused, tvb, *offsetp, 1,
                               do_red_green_blue & 0xf8);
      } else
          proto_tree_add_uint_format(t, hf_x11_coloritem_flags, tvb, *offsetp, 1, do_red_green_blue,
                               "flags: none");
      *offsetp += 1;
}

static void gravity(tvbuff_t *tvb, int *offsetp, proto_tree *t,
    int hf, const char *nullInterpretation)
{
      guint8 v = VALUE8(tvb, *offsetp);

      if (!v)
          proto_tree_add_uint_format(t, hf, tvb, *offsetp, 1, v, "%s: 0 (%s)",
                               proto_registrar_get_nth(hf) -> name,
                               nullInterpretation);
      else
          proto_tree_add_uint(t, hf, tvb, *offsetp, 1, v);
      *offsetp += 1;
}

static void listOfArc(tvbuff_t *tvb, int *offsetp, proto_tree *t, int hf,
                  int length, gboolean little_endian)
{
      proto_item *ti = proto_tree_add_item(t, hf, tvb, *offsetp, length * 8, little_endian);
      proto_tree *tt = proto_item_add_subtree(ti, ett_x11_list_of_arc);
      while(length--) {
          gint16 x = VALUE16(tvb, *offsetp);
          gint16 y = VALUE16(tvb, *offsetp + 2);
          guint16 width = VALUE16(tvb, *offsetp + 4);
          guint16 height = VALUE16(tvb, *offsetp + 6);
          gint16 angle1 = VALUE16(tvb, *offsetp + 8);
          gint16 angle2 = VALUE16(tvb, *offsetp + 10);

          proto_item *tti = proto_tree_add_none_format(tt, hf_x11_arc, tvb, *offsetp, 12,
                                               "arc: %dx%d+%d+%d, angle %d -> %d (%f degrees -> %f degrees)",
                                               width, height, x, y, angle1, angle2,
                                               angle1 / 64.0, angle2 / 64.0);
          proto_tree *ttt = proto_item_add_subtree(tti, ett_x11_arc);
          proto_tree_add_int(ttt, hf_x11_arc_x, tvb, *offsetp, 2, x);
          *offsetp += 2;
          proto_tree_add_int(ttt, hf_x11_arc_y, tvb, *offsetp, 2, y);
          *offsetp += 2;
          proto_tree_add_uint(ttt, hf_x11_arc_width, tvb, *offsetp, 2, y);
          *offsetp += 2;
          proto_tree_add_uint(ttt, hf_x11_arc_height, tvb, *offsetp, 2, y);
          *offsetp += 2;
          proto_tree_add_int(ttt, hf_x11_arc_angle1, tvb, *offsetp, 2, y);
          *offsetp += 2;
          proto_tree_add_int(ttt, hf_x11_arc_angle2, tvb, *offsetp, 2, y);
          *offsetp += 2;
      }
}

static void listOfAtom(tvbuff_t *tvb, int *offsetp, proto_tree *t, int hf,
                   int length, gboolean little_endian)
{
      proto_item *ti = proto_tree_add_item(t, hf, tvb, *offsetp, length * 4, little_endian);
      proto_tree *tt = proto_item_add_subtree(ti, ett_x11_list_of_atom);
      while(length--)
          atom(tvb, offsetp, tt, hf_x11_properties_item, little_endian);
}

static void listOfByte(tvbuff_t *tvb, int *offsetp, proto_tree *t, int hf,
                   int length, gboolean little_endian)
{
      if (length <= 0) length = 1;
      proto_tree_add_item(t, hf, tvb, *offsetp, length, little_endian);
      *offsetp += length;
}

static void listOfCard32(tvbuff_t *tvb, int *offsetp, proto_tree *t, int hf,
                   int hf_item, int length, gboolean little_endian)
{
      proto_item *ti = proto_tree_add_item(t, hf, tvb, *offsetp, length * 4, little_endian);
      proto_tree *tt = proto_item_add_subtree(ti, ett_x11_list_of_card32);
      while(length--) {
          proto_tree_add_uint(tt, hf_item, tvb, *offsetp, 4, VALUE32(tvb, *offsetp));
          *offsetp += 4;
      }
}

static void listOfColorItem(tvbuff_t *tvb, int *offsetp, proto_tree *t, int hf,
                      int length, gboolean little_endian)
{
      proto_item *ti = proto_tree_add_item(t, hf, tvb, *offsetp, length * 8, little_endian);
      proto_tree *tt = proto_item_add_subtree(ti, ett_x11_list_of_color_item);
      while(length--) {
          proto_item *tti;
          proto_tree *ttt;
          unsigned do_red_green_blue;
          guint16 red, green, blue;
          char buffer[1024];
          char *bp;
          const char *sep;

          red = VALUE16(tvb, *offsetp + 4);
          green = VALUE16(tvb, *offsetp + 6);
          blue = VALUE16(tvb, *offsetp + 8);
          do_red_green_blue = VALUE8(tvb, *offsetp + 10);

          bp = buffer + sprintf(buffer, "colorItem: ");
          sep = "";
          if (do_red_green_blue & 0x1) {
            bp += sprintf(bp, "red = %d", red);
            sep = ", ";
          }
          if (do_red_green_blue & 0x2) {
            bp += sprintf(bp, "%sgreen = %d", sep, green);
            sep = ", ";
          }
          if (do_red_green_blue & 0x4)
            bp += sprintf(bp, "%sblue = %d", sep, blue);

          tti = proto_tree_add_none_format(tt, hf_x11_coloritem, tvb, *offsetp, 12, "%s", buffer);
          ttt = proto_item_add_subtree(tti, ett_x11_color_item);
          proto_tree_add_item(ttt, hf_x11_coloritem_pixel, tvb, *offsetp, 4, little_endian);
          *offsetp += 4;
          proto_tree_add_item(ttt, hf_x11_coloritem_red, tvb, *offsetp, 2, little_endian);
          *offsetp += 2;
          proto_tree_add_item(ttt, hf_x11_coloritem_green, tvb, *offsetp, 2, little_endian);
          *offsetp += 2;
          proto_tree_add_item(ttt, hf_x11_coloritem_blue, tvb, *offsetp, 2, little_endian);
          *offsetp += 2;
          colorFlags(tvb, offsetp, ttt);
          proto_tree_add_item(ttt, hf_x11_coloritem_unused, tvb, *offsetp, 1, little_endian);
          *offsetp += 1;
      }
}

static GTree *keysymTable = NULL;

static gint compareGuint32(gconstpointer a, gconstpointer b)
{
      return GPOINTER_TO_INT(b) - GPOINTER_TO_INT(a);
}

static void
XConvertCase(register int sym, int *lower, int *upper)
{
    *lower = sym;
    *upper = sym;
    switch(sym >> 8) {
    case 0: /* Latin 1 */
      if ((sym >= XK_A) && (sym <= XK_Z))
          *lower += (XK_a - XK_A);
      else if ((sym >= XK_a) && (sym <= XK_z))
          *upper -= (XK_a - XK_A);
      else if ((sym >= XK_Agrave) && (sym <= XK_Odiaeresis))
          *lower += (XK_agrave - XK_Agrave);
      else if ((sym >= XK_agrave) && (sym <= XK_odiaeresis))
          *upper -= (XK_agrave - XK_Agrave);
      else if ((sym >= XK_Ooblique) && (sym <= XK_Thorn))
          *lower += (XK_oslash - XK_Ooblique);
      else if ((sym >= XK_oslash) && (sym <= XK_thorn))
          *upper -= (XK_oslash - XK_Ooblique);
      break;
    case 1: /* Latin 2 */
      /* Assume the KeySym is a legal value (ignore discontinuities) */
      if (sym == XK_Aogonek)
          *lower = XK_aogonek;
      else if (sym >= XK_Lstroke && sym <= XK_Sacute)
          *lower += (XK_lstroke - XK_Lstroke);
      else if (sym >= XK_Scaron && sym <= XK_Zacute)
          *lower += (XK_scaron - XK_Scaron);
      else if (sym >= XK_Zcaron && sym <= XK_Zabovedot)
          *lower += (XK_zcaron - XK_Zcaron);
      else if (sym == XK_aogonek)
          *upper = XK_Aogonek;
      else if (sym >= XK_lstroke && sym <= XK_sacute)
          *upper -= (XK_lstroke - XK_Lstroke);
      else if (sym >= XK_scaron && sym <= XK_zacute)
          *upper -= (XK_scaron - XK_Scaron);
      else if (sym >= XK_zcaron && sym <= XK_zabovedot)
          *upper -= (XK_zcaron - XK_Zcaron);
      else if (sym >= XK_Racute && sym <= XK_Tcedilla)
          *lower += (XK_racute - XK_Racute);
      else if (sym >= XK_racute && sym <= XK_tcedilla)
          *upper -= (XK_racute - XK_Racute);
      break;
    case 2: /* Latin 3 */
      /* Assume the KeySym is a legal value (ignore discontinuities) */
      if (sym >= XK_Hstroke && sym <= XK_Hcircumflex)
          *lower += (XK_hstroke - XK_Hstroke);
      else if (sym >= XK_Gbreve && sym <= XK_Jcircumflex)
          *lower += (XK_gbreve - XK_Gbreve);
      else if (sym >= XK_hstroke && sym <= XK_hcircumflex)
          *upper -= (XK_hstroke - XK_Hstroke);
      else if (sym >= XK_gbreve && sym <= XK_jcircumflex)
          *upper -= (XK_gbreve - XK_Gbreve);
      else if (sym >= XK_Cabovedot && sym <= XK_Scircumflex)
          *lower += (XK_cabovedot - XK_Cabovedot);
      else if (sym >= XK_cabovedot && sym <= XK_scircumflex)
          *upper -= (XK_cabovedot - XK_Cabovedot);
      break;
    case 3: /* Latin 4 */
      /* Assume the KeySym is a legal value (ignore discontinuities) */
      if (sym >= XK_Rcedilla && sym <= XK_Tslash)
          *lower += (XK_rcedilla - XK_Rcedilla);
      else if (sym >= XK_rcedilla && sym <= XK_tslash)
          *upper -= (XK_rcedilla - XK_Rcedilla);
      else if (sym == XK_ENG)
          *lower = XK_eng;
      else if (sym == XK_eng)
          *upper = XK_ENG;
      else if (sym >= XK_Amacron && sym <= XK_Umacron)
          *lower += (XK_amacron - XK_Amacron);
      else if (sym >= XK_amacron && sym <= XK_umacron)
          *upper -= (XK_amacron - XK_Amacron);
      break;
    case 6: /* Cyrillic */
      /* Assume the KeySym is a legal value (ignore discontinuities) */
      if (sym >= XK_Serbian_DJE && sym <= XK_Serbian_DZE)
          *lower -= (XK_Serbian_DJE - XK_Serbian_dje);
      else if (sym >= XK_Serbian_dje && sym <= XK_Serbian_dze)
          *upper += (XK_Serbian_DJE - XK_Serbian_dje);
      else if (sym >= XK_Cyrillic_YU && sym <= XK_Cyrillic_HARDSIGN)
          *lower -= (XK_Cyrillic_YU - XK_Cyrillic_yu);
      else if (sym >= XK_Cyrillic_yu && sym <= XK_Cyrillic_hardsign)
          *upper += (XK_Cyrillic_YU - XK_Cyrillic_yu);
        break;
    case 7: /* Greek */
      /* Assume the KeySym is a legal value (ignore discontinuities) */
      if (sym >= XK_Greek_ALPHAaccent && sym <= XK_Greek_OMEGAaccent)
          *lower += (XK_Greek_alphaaccent - XK_Greek_ALPHAaccent);
      else if (sym >= XK_Greek_alphaaccent && sym <= XK_Greek_omegaaccent &&
             sym != XK_Greek_iotaaccentdieresis &&
             sym != XK_Greek_upsilonaccentdieresis)
          *upper -= (XK_Greek_alphaaccent - XK_Greek_ALPHAaccent);
      else if (sym >= XK_Greek_ALPHA && sym <= XK_Greek_OMEGA)
          *lower += (XK_Greek_alpha - XK_Greek_ALPHA);
      else if (sym >= XK_Greek_alpha && sym <= XK_Greek_omega &&
             sym != XK_Greek_finalsmallsigma)
          *upper -= (XK_Greek_alpha - XK_Greek_ALPHA);
        break;
    }
}

static const char *
keycode2keysymString(int *keycodemap[256], int first_keycode,
                 int keysyms_per_keycode, 
                 int *modifiermap[array_length(modifiers)],
                 int keycodes_per_modifier,
                 guint32 keycode, guint32 bitmask)
{
      static char buf[32];
      int *syms;
      int groupmodkc, numlockkc, numlockmod, groupmod;
      int lockmod_is_capslock = 0, lockmod_is_shiftlock = 0;
      int lockmod_is_nosymbol = 1;
      int modifier, kc, keysym;

      if ((syms = keycodemap[keycode]) == NULL)
            return "<Unknown>";

      for (kc = first_keycode, groupmodkc = numlockkc = -1; kc < 256; ++kc)
            for (keysym = 0; keysym < keysyms_per_keycode; ++keysym) {
                  if (keycodemap[kc] == NULL)
                        return "<Unknown>";
                  switch (keycodemap[kc][keysym]) {
                        case 0xff7e:
                              groupmodkc = kc;
                              break;

                        case 0xff7f:
                              numlockkc = kc;
                              break;

                        case 0xffe5:
                              lockmod_is_capslock = kc;
                              break;

                        case 0xffe6:
                              lockmod_is_shiftlock = kc;
                              break;
                  }
            }


      /*
       * If we have not seen the modifiermap we don't know what the
       * keycode translates to, but we do know it's one of the keys 
       * in syms (give or take a case-conversion), so we could in 
       * theory list them all.
       */
      if (modifiermap[array_length(modifiers) - 1] == NULL) /* all or none */
            return "<Unknown>";

      /* find out what the numlockmodifer and groupmodifier is. */
      for (modifier = 0, numlockmod = groupmod = -1;
          modifier < (int)array_length(modifiers) && numlockmod == -1;
          ++modifier)
            for (kc = 0; kc < keycodes_per_modifier; ++kc)
                  if (modifiermap[modifier][kc] == numlockkc)
                        numlockmod = modifier;
                  else if (modifiermap[modifier][kc] == groupmodkc)
                        groupmod = modifier;

      /*
       * ... and what the lockmodifier is interpreted as.
       * (X11v4r6 ref, keyboard and pointers section.)
       */
      for (kc = 0; kc < keycodes_per_modifier; ++kc)
            if (modifiermap[1][kc] == lockmod_is_capslock) {
                  lockmod_is_shiftlock = lockmod_is_nosymbol = 0;
                  break;
            }
            else if (modifiermap[0][kc] == lockmod_is_shiftlock) {
                  lockmod_is_capslock = lockmod_is_nosymbol = 0;
                  break;
            }

#if 0 
      /* 
       * This is (how I understand) the X11v4R6 protocol description given
       * in A. Nye's book.  It is quite different from the
       * code in _XTranslateKey() in the file 
       * "$XConsortium: KeyBind.c /main/55 1996/02/02 14:08:55 kaleb $"
       * as shipped with XFree, and doesn't work correctly, nor do I see
       * how it could (e.g. the case of lower/uppercase-letters).
       * -- Michael Shuldman
       */

      if (numlockmod >= 0 && (bitmask & modifiermask[numlockmod])
          && ((syms[1] >= 0xff80
           && syms[1] <= 0xffbd)
           || (syms[1] >= 0x11000000
            && syms[1] <= 0x1100ffff))) {
            if ((bitmask & ShiftMask) || lockmod_is_shiftlock)
                  return keysymString(syms[groupmod + 0]);
            else
                  if (syms[groupmod + 1] == NoSymbol)
                        return keysymString(syms[groupmod + 0]);
                  else
                        return keysymString(syms[groupmod + 1]);
      }
      else if (!(bitmask & ShiftMask) && !(bitmask & LockMask))
            return keysymString(syms[groupmod + 0]);
      else if (!(bitmask & ShiftMask)
          && ((bitmask & LockMask) && lockmod_is_capslock))
            if (islower(syms[groupmod + 0]))
/*                return toupper(keysymString(syms[groupmod + 0])); */
                  return "Uppercase"; /* XXX */
            else
                  return keysymString(syms[groupmod + 0]);

      else if ((bitmask & ShiftMask) 
          && ((bitmask & LockMask) && lockmod_is_capslock))
            if (islower(syms[groupmod + 1]))
/*                return toupper(keysymString(syms[groupmod + 1])); */
                  return "Uppercase"; /* XXX */
            else
                  return keysymString(syms[groupmod + 1]);

      else if ((bitmask & ShiftMask) 
          ||  ((bitmask & LockMask) && lockmod_is_shiftlock))
                  return keysymString(syms[groupmod + 1]);
#else /* _XTranslateKey() based code. */

      while (keysyms_per_keycode > 2
          && keycodemap[keysyms_per_keycode - 1] == NoSymbol)
            --keysyms_per_keycode;
      if (keysyms_per_keycode > 2
          && (groupmod >= 0 && (modifiermask[groupmod] & bitmask))) {
            syms += 2;
            keysyms_per_keycode -= 2;
      }
      
      if (numlockmod >= 0 && (bitmask & modifiermask[numlockmod])
          && keysyms_per_keycode > 1
          && ((syms[1] >= 0xff80 && syms[1] <= 0xffbd)
           || (syms[1] >= 0x11000000 && syms[1] <= 0x1100ffff))) {
            if ((bitmask & ShiftMask)
                || (bitmask & LockMask && lockmod_is_shiftlock))
                  keysym = syms[0];
            else
                  keysym = syms[1];
      }
      else if (!(bitmask & ShiftMask)
          && (!(bitmask & LockMask) || lockmod_is_nosymbol)) {
            if (keysyms_per_keycode == 1
                || (keysyms_per_keycode > 1 && syms[1] == NoSymbol)) {
                  int usym;

                  XConvertCase(syms[0], &keysym, &usym);
            }
            else
                  keysym = syms[0];
      }
      else if (!(bitmask & LockMask) || !lockmod_is_capslock) {
            int lsym, usym;

            if (keysyms_per_keycode == 1
                || (keysyms_per_keycode > 1 && (usym = syms[1]) == NoSymbol))
                  XConvertCase(syms[0], &lsym, &usym);
            keysym = usym;
      }
      else {
            int lsym, usym;

            if (keysyms_per_keycode == 1
                || (keysyms_per_keycode > 1 && syms[1] == NoSymbol))
                  keysym = syms[0];

            XConvertCase(keysym, &lsym, &usym);

            if (!(bitmask & ShiftMask) && keysym != syms[0]
            && ((keysym != usym) || (lsym == usym)))
                  XConvertCase(syms[0], &lsym, &usym);
            keysym = usym;
      }
      
      if (keysym == XK_VoidSymbol)
            keysym = NoSymbol;

      sprintf(buf, "%d, \"%s\"", keysym, keysymString(keysym));
      return buf;
#endif
}

static const char *keysymString(guint32 v)
{
      gpointer res;
      if (!keysymTable) {

            /* This table is so big that we built it only if necessary */

          const value_string *p = keysym_vals_source;
          keysymTable = g_tree_new(compareGuint32);
          for(; p -> strptr; p++)
              g_tree_insert(keysymTable, GINT_TO_POINTER(p -> value), p -> strptr);
      }
      res = g_tree_lookup(keysymTable, GINT_TO_POINTER(v));
      return res ? res : "<Unknown>";
}

static void listOfKeycode(tvbuff_t *tvb, int *offsetp, proto_tree *t, int hf,
                    int *modifiermap[], int keycodes_per_modifier,
                    gboolean little_endian)
{
      proto_item *ti = proto_tree_add_item(t, hf, tvb, *offsetp,
        array_length(modifiers) * keycodes_per_modifier, little_endian);
      proto_tree *tt = proto_item_add_subtree(ti, ett_x11_list_of_keycode);
      size_t m;

      for (m = 0; m < array_length(modifiers);
        ++m, *offsetp += keycodes_per_modifier) {
          const guint8 *p;
          proto_item *tikc;
          int i;

          p = tvb_get_ptr(tvb, *offsetp, keycodes_per_modifier);
          modifiermap[m] =
              g_malloc(sizeof(*modifiermap[m]) * keycodes_per_modifier);

          tikc = proto_tree_add_bytes_format(tt, hf_x11_keycodes_item, tvb,
              *offsetp, keycodes_per_modifier, p, "item: ");
          for(i = 0; i < keycodes_per_modifier; ++i) {
            guchar c = p[i];

            if (c)
                proto_item_append_text(tikc, " %s=%d", modifiers[m], c);

            modifiermap[m][i] = c;
          }
      }
}

static void listOfKeysyms(tvbuff_t *tvb, int *offsetp, proto_tree *t, int hf,
                    int hf_item, int *keycodemap[256],
                    int keycode_first, int keycode_count,
                    int keysyms_per_keycode, gboolean little_endian)
{
      proto_item *ti = proto_tree_add_item(t, hf, tvb, *offsetp, keycode_count * keysyms_per_keycode * 4, little_endian);
      proto_tree *tt = proto_item_add_subtree(ti, ett_x11_list_of_keysyms);
      proto_item *tti;
      proto_tree *ttt;
      int i, keycode;

      g_assert(keycode_first >= 0);
      g_assert(keycode_count >= 0);

      for (keycode = keycode_first; keycode_count > 0;
           ++keycode, --keycode_count) {
          if (keycode >= 256) {
            proto_tree_add_text(tt, tvb, *offsetp, 4 * keysyms_per_keycode,
                "keycode value %d is out of range", keycode);
            *offsetp += 4 * keysyms_per_keycode;
            continue;
          }
          tti = proto_tree_add_none_format(tt, hf_item, tvb, *offsetp,
            4 * keysyms_per_keycode, "keysyms (keycode %d):", keycode);

          ttt = proto_item_add_subtree(tti, ett_x11_keysym);

          tvb_ensure_bytes_exist(tvb, *offsetp, 4 * keysyms_per_keycode);
          keycodemap[keycode]
              = g_malloc(sizeof(*keycodemap[keycode]) * keysyms_per_keycode);

          for(i = 0; i < keysyms_per_keycode; ++i) {
              /* keysymvalue = byte3 * 256 + byte4. */
              guint32 v = VALUE32(tvb, *offsetp);

              proto_item_append_text(tti, " %s", keysymString(v));
              proto_tree_add_uint_format(ttt, hf_x11_keysyms_item_keysym,
                  tvb, *offsetp, 4, v,
                  "keysym (keycode %d): 0x%08x (%s)",
                  keycode, v, keysymString(v));

              keycodemap[keycode][i] = v;
              *offsetp += 4;
          }
      
          for (i = 1; i < keysyms_per_keycode; ++i)
            if (keycodemap[keycode][i] != NoSymbol)
                  break;

          if (i == keysyms_per_keycode) {
              /* all but (possibly) first were NoSymbol. */
            if (keysyms_per_keycode == 4) {
                  keycodemap[keycode][1] = NoSymbol;
                  keycodemap[keycode][2] = keycodemap[keycode][0];
                  keycodemap[keycode][3] = NoSymbol;
            }

            continue;
          }

          for (i = 2; i < keysyms_per_keycode; ++i)
            if (keycodemap[keycode][i] != NoSymbol)
                  break;
          if (i == keysyms_per_keycode) {
              /* all but (possibly) first two were NoSymbol. */
            if (keysyms_per_keycode == 4) {
                  keycodemap[keycode][2] = keycodemap[keycode][0];
                  keycodemap[keycode][3] =  keycodemap[keycode][1];
            }

            continue;
          }
      }
}

static void listOfPoint(tvbuff_t *tvb, int *offsetp, proto_tree *t, int hf,
                  int length, gboolean little_endian)
{
      proto_item *ti = proto_tree_add_item(t, hf, tvb, *offsetp, length * 4, little_endian);
      proto_tree *tt = proto_item_add_subtree(ti, ett_x11_list_of_point);
      while(length--) {
          gint16 x, y;
          proto_item *tti;
          proto_tree *ttt;

          x = VALUE16(tvb, *offsetp);
          y = VALUE16(tvb, *offsetp + 2);

          tti = proto_tree_add_none_format(tt, hf_x11_point, tvb, *offsetp, 4, "point: (%d,%d)", x, y);
          ttt = proto_item_add_subtree(tti, ett_x11_point);
          proto_tree_add_int(ttt, hf_x11_point_x, tvb, *offsetp, 2, x);
          *offsetp += 2;
          proto_tree_add_int(ttt, hf_x11_point_y, tvb, *offsetp, 2, y);
          *offsetp += 2;
      }
}

static void listOfRectangle(tvbuff_t *tvb, int *offsetp, proto_tree *t, int hf,
                      int length, gboolean little_endian)
{
      proto_item *ti = proto_tree_add_item(t, hf, tvb, *offsetp, length * 8, little_endian);
      proto_tree *tt = proto_item_add_subtree(ti, ett_x11_list_of_rectangle);
      while(length--) {
          gint16 x, y;
          unsigned width, height;
          proto_item *tti;
          proto_tree *ttt;

          x = VALUE16(tvb, *offsetp);
          y = VALUE16(tvb, *offsetp + 2);
          width = VALUE16(tvb, *offsetp + 4);
          height = VALUE16(tvb, *offsetp + 6);

          tti = proto_tree_add_none_format(tt, hf_x11_rectangle, tvb, *offsetp, 8,
                                     "rectangle: %dx%d+%d+%d", width, height, x, y);
          ttt = proto_item_add_subtree(tti, ett_x11_rectangle);
          proto_tree_add_int(ttt, hf_x11_rectangle_x, tvb, *offsetp, 2, x);
          *offsetp += 2;
          proto_tree_add_int(ttt, hf_x11_rectangle_y, tvb, *offsetp, 2, y);
          *offsetp += 2;
          proto_tree_add_uint(ttt, hf_x11_rectangle_width, tvb, *offsetp, 2, width);
          *offsetp += 2;
          proto_tree_add_uint(ttt, hf_x11_rectangle_height, tvb, *offsetp, 2, height);
          *offsetp += 2;
      }
}

static void listOfSegment(tvbuff_t *tvb, int *offsetp, proto_tree *t, int hf,
                    int length, gboolean little_endian)
{
      proto_item *ti = proto_tree_add_item(t, hf, tvb, *offsetp, length * 8, little_endian);
      proto_tree *tt = proto_item_add_subtree(ti, ett_x11_list_of_segment);
      while(length--) {
          gint16 x1, y1, x2, y2;
          proto_item *tti;
          proto_tree *ttt;

          x1 = VALUE16(tvb, *offsetp);
          y1 = VALUE16(tvb, *offsetp + 2);
          x2 = VALUE16(tvb, *offsetp + 4);
          y2 = VALUE16(tvb, *offsetp + 6);

          tti = proto_tree_add_none_format(tt, hf_x11_segment, tvb, *offsetp, 8,
                                     "segment: (%d,%d)-(%d,%d)", x1, y1, x2, y2);
          ttt = proto_item_add_subtree(tti, ett_x11_segment);
          proto_tree_add_item(ttt, hf_x11_segment_x1, tvb, *offsetp, 2, little_endian);
          *offsetp += 2;
          proto_tree_add_item(ttt, hf_x11_segment_y1, tvb, *offsetp, 2, little_endian);
          *offsetp += 2;
          proto_tree_add_item(ttt, hf_x11_segment_x2, tvb, *offsetp, 2, little_endian);
          *offsetp += 2;
          proto_tree_add_item(ttt, hf_x11_segment_y2, tvb, *offsetp, 2, little_endian);
          *offsetp += 2;
      }
}

/* XXX - the protocol tree code should handle non-printable characters.
   Note that "non-printable characters" may depend on your locale.... */
static void stringCopy(char *dest, const char *source, int length)
{
      guchar c;
      while(length--) {
          c = *source++;
          if (!isgraph(c) && c != ' ') c = '.';
          *dest++ = c;
      }
      *dest++ = '\0';
}

static void listOfString8(tvbuff_t *tvb, int *offsetp, proto_tree *t, int hf,
                    int hf_item, int length, gboolean little_endian)
{
      char *s = NULL;
      guint allocated = 0;
      proto_item *ti;
      proto_tree *tt;
      int i;

      /* Compute total length */

      int scanning_offset = *offsetp; /* Scanning pointer */
      int l;
      for(i = length; i; i--) {
          l = tvb_get_guint8(tvb, scanning_offset);
          scanning_offset += 1 + l;
      }

      ti = proto_tree_add_item(t, hf, tvb, *offsetp, scanning_offset - *offsetp, little_endian);
      tt = proto_item_add_subtree(ti, ett_x11_list_of_string8);

      /*
       * In case we throw an exception, clean up whatever stuff we've
       * allocated (if any).
       */
      CLEANUP_PUSH(g_free, s);

      while(length--) {
          unsigned l = VALUE8(tvb, *offsetp);
          if (allocated < (l + 1)) {
              /* g_realloc doesn't work ??? */
              g_free(s);
              s = g_malloc(l + 1);
              allocated = l + 1;
          }
          stringCopy(s, tvb_get_ptr(tvb, *offsetp + 1, l), l); /* Nothing better for now. We need a better string handling API. */
          proto_tree_add_string_format(tt, hf_item, tvb, *offsetp, l + 1, s, "\"%s\"", s);
          *offsetp += l + 1;
      }

      /*
       * Call the cleanup handler to free the string and pop the handler.
       */
      CLEANUP_CALL_AND_POP;
}

#define STRING16_MAX_DISPLAYED_LENGTH 150

static int stringIsActuallyAn8BitString(tvbuff_t *tvb, int offset, unsigned length)
{
      if (length > STRING16_MAX_DISPLAYED_LENGTH) length = STRING16_MAX_DISPLAYED_LENGTH;
      for(; length > 0; offset += 2, length--) {
          if (tvb_get_guint8(tvb, offset))
            return FALSE;
      }
      return TRUE;
}

/* length is the length of the _byte_zone_ (that is, twice the length of the string) */

static void string16_with_buffer_preallocated(tvbuff_t *tvb, proto_tree *t,
                                    int hf, int hf_bytes,
                                    int offset, unsigned length,
                                    char **s, int *sLength,
                                    gboolean little_endian)
{
      int truncated = FALSE;
      unsigned l = length / 2;

      if (stringIsActuallyAn8BitString(tvb, offset, l)) {
          char *dp;
          int soffset = offset;

          if (l > STRING16_MAX_DISPLAYED_LENGTH) {
              truncated = TRUE;
              l = STRING16_MAX_DISPLAYED_LENGTH;
          }
          if (*sLength < (int) l + 3) {
              g_free(*s);
              *s = g_malloc(l + 3);
              *sLength = l + 3;
          }
          dp = *s;
          *dp++ = '"';
          if (truncated) l -= 3;

          while(l--) {
              soffset++;
              *dp++ = tvb_get_guint8(tvb, soffset);
              soffset++;
          }
          *dp++ = '"';

          /* If truncated, add an ellipsis */
          if (truncated) { *dp++ = '.'; *dp++ = '.'; *dp++ = '.'; }

          *dp++ = '\0';
          proto_tree_add_string_format(t, hf, tvb, offset, length, tvb_get_ptr(tvb, offset, length), "%s: %s",
                              proto_registrar_get_nth(hf) -> name, *s);
      } else
          proto_tree_add_item(t, hf_bytes, tvb, offset, length, little_endian);

}

static void listOfTextItem(tvbuff_t *tvb, int *offsetp, proto_tree *t, int hf,
    int sizeIs16, int next_offset, gboolean little_endian)
{
      int allocated = 0;
      char *s = NULL;
      proto_item *ti;
      proto_tree *tt;
      guint32 fid;

      /* Compute total length */

      int scanning_offset = *offsetp; /* Scanning pointer */
      int l;                            /* Length of an individual item */
      int n = 0;                        /* Number of items */

      while(scanning_offset < next_offset) {
          l = tvb_get_guint8(tvb, scanning_offset);
          scanning_offset++;
          if (!l) break;
          n++;
          scanning_offset += l == 255 ? 4 : l + (sizeIs16 ? l : 0) + 1;
      }

      ti = proto_tree_add_item(t, hf, tvb, *offsetp, scanning_offset - *offsetp, little_endian);
      tt = proto_item_add_subtree(ti, ett_x11_list_of_text_item);

      /*
       * In case we throw an exception, clean up whatever stuff we've
       * allocated (if any).
       */
      CLEANUP_PUSH(g_free, s);

      while(n--) {
          unsigned l = VALUE8(tvb, *offsetp);
          if (l == 255) { /* Item is a font */
              fid = tvb_get_ntohl(tvb, *offsetp + 1);
              proto_tree_add_uint(tt, hf_x11_textitem_font, tvb, *offsetp, 5, fid);
              *offsetp += 5;
          } else { /* Item is a string */
              proto_item *tti;
              proto_tree *ttt;
              gint8 delta = VALUE8(tvb, *offsetp + 1);
              if (sizeIs16) l += l;
              if ((unsigned) allocated < l + 1) {
                  /* g_realloc doesn't work ??? */
                  g_free(s);
                  s = g_malloc(l + 1);
                  allocated = l + 1;
              }
              stringCopy(s, tvb_get_ptr(tvb, *offsetp + 2, l), l);
              tti = proto_tree_add_none_format(tt, hf_x11_textitem_string, tvb, *offsetp, l + 2,
                                           "textitem (string): delta = %d, \"%s\"",
                                           delta, s);
              ttt = proto_item_add_subtree(tti, ett_x11_text_item);
              proto_tree_add_item(ttt, hf_x11_textitem_string_delta, tvb, *offsetp + 1, 1, little_endian);
              if (sizeIs16)
                  string16_with_buffer_preallocated(tvb, ttt, hf_x11_textitem_string_string16,
                                            hf_x11_textitem_string_string16_bytes,
                                            *offsetp + 2, l,
                                            &s, &allocated,
                                            little_endian);
              else
                  proto_tree_add_string_format(ttt, hf_x11_textitem_string_string8, tvb,
                                         *offsetp + 2, l, s, "\"%s\"", s);
              *offsetp += l + 2;
          }
      }

      /*
       * Call the cleanup handler to free the string and pop the handler.
       */
      CLEANUP_CALL_AND_POP;
}

static guint32 field8(tvbuff_t *tvb, int *offsetp, proto_tree *t, int hf,
                  gboolean little_endian)
{
      guint32 v = VALUE8(tvb, *offsetp);
      header_field_info *hfi = proto_registrar_get_nth(hf);
      gchar *enumValue = NULL;

      if (hfi -> strings)
          enumValue = match_strval(v, cVALS(hfi -> strings));
      if (enumValue)
          proto_tree_add_uint_format(t, hf, tvb, *offsetp, 1, v,
            hfi -> display == BASE_DEC ? "%s: %u (%s)" : "%s: 0x%02x (%s)",
          hfi -> name, v, enumValue);
      else
          proto_tree_add_item(t, hf, tvb, *offsetp, 1, little_endian);
      *offsetp += 1;
      return v;
}

static guint32 field16(tvbuff_t *tvb, int *offsetp, proto_tree *t, int hf,
                   gboolean little_endian)
{
      guint32 v = VALUE16(tvb, *offsetp);
      header_field_info *hfi = proto_registrar_get_nth(hf);
      gchar *enumValue = NULL;

      if (hfi -> strings)
          enumValue = match_strval(v, cVALS(hfi -> strings));
      if (enumValue)
          proto_tree_add_uint_format(t, hf, tvb, *offsetp, 2, v,
                hfi -> display == BASE_DEC ? "%s: %u (%s)" : "%s: 0x%02x (%s)",
          hfi -> name, v, enumValue);
      else
          proto_tree_add_item(t, hf, tvb, *offsetp, 2, little_endian);
      *offsetp += 2;
      return v;
}

static guint32 field32(tvbuff_t *tvb, int *offsetp, proto_tree *t, int hf,
                   gboolean little_endian)
{
      guint32 v = VALUE32(tvb, *offsetp);
      header_field_info *hfi = proto_registrar_get_nth(hf);
      gchar *enumValue = NULL;
      gchar *nameAsChar = hfi -> name;

      if (hfi -> strings)
          enumValue = match_strval(v, cVALS(hfi -> strings));
      if (enumValue)
          proto_tree_add_uint_format(t, hf, tvb, *offsetp, 4, v,
                               hfi -> display == BASE_DEC ? "%s: %u (%s)" : "%s: 0x%08x (%s)",
                               nameAsChar, v, enumValue);
      else
          proto_tree_add_uint_format(t, hf, tvb, *offsetp, 4, v,
                               hfi -> display == BASE_DEC ? "%s: %u" : "%s: 0x%08x",
                               nameAsChar, v);
      *offsetp += 4;
      return v;
}

static void gcAttributes(tvbuff_t *tvb, int *offsetp, proto_tree *t,
                   gboolean little_endian)
{
      BITMASK32(gc_value);
      BITFIELD(ENUM8,  gc_value_mask, function);
      BITFIELD(CARD32, gc_value_mask, plane_mask);
      BITFIELD(CARD32, gc_value_mask, foreground);
      BITFIELD(CARD32, gc_value_mask, background);
      BITFIELD(CARD16, gc_value_mask, line_width);
      BITFIELD(ENUM8,  gc_value_mask, line_style);
      BITFIELD(ENUM8,  gc_value_mask, cap_style);
      BITFIELD(ENUM8,  gc_value_mask, join_style);
      BITFIELD(ENUM8,  gc_value_mask, fill_style);
      BITFIELD(ENUM8,  gc_value_mask, fill_rule);
      BITFIELD(PIXMAP, gc_value_mask, tile);
      BITFIELD(PIXMAP, gc_value_mask, stipple);
      BITFIELD(INT16,  gc_value_mask, tile_stipple_x_origin);
      BITFIELD(INT16,  gc_value_mask, tile_stipple_y_origin);
      BITFIELD(FONT,   gc_value_mask, font);
      BITFIELD(ENUM8,  gc_value_mask, subwindow_mode);
      BITFIELD(BOOL,   gc_value_mask, graphics_exposures);
      BITFIELD(INT16,  gc_value_mask, clip_x_origin);
      BITFIELD(INT16,  gc_value_mask, clip_y_origin);
      BITFIELD(PIXMAP, gc_value_mask, clip_mask);
      BITFIELD(CARD16, gc_value_mask, dash_offset);
      BITFIELD(CARD8,  gc_value_mask, gc_dashes);
      BITFIELD(ENUM8,  gc_value_mask, arc_mode);
      ENDBITMASK;
}

static void gcMask(tvbuff_t *tvb, int *offsetp, proto_tree *t,
               gboolean little_endian)
{
      BITMASK32(gc_value);
      FLAG(gc_value, function);
      FLAG(gc_value, plane_mask);
      FLAG(gc_value, foreground);
      FLAG(gc_value, background);
      FLAG(gc_value, line_width);
      FLAG(gc_value, line_style);
      FLAG(gc_value, cap_style);
      FLAG(gc_value, join_style);
      FLAG(gc_value, fill_style);
      FLAG(gc_value, fill_rule);
      FLAG(gc_value, tile);
      FLAG(gc_value, stipple);
      FLAG(gc_value, tile_stipple_x_origin);
      FLAG(gc_value, tile_stipple_y_origin);
      FLAG(gc_value, font);
      FLAG(gc_value, subwindow_mode);
      FLAG(gc_value, graphics_exposures);
      FLAG(gc_value, clip_x_origin);
      FLAG(gc_value, clip_y_origin);
      FLAG(gc_value, clip_mask);
      FLAG(gc_value, dash_offset);
      FLAG(gc_value, gc_dashes);
      FLAG(gc_value, arc_mode);
      ENDBITMASK;
}

static guint32 requestLength(tvbuff_t *tvb, int *offsetp, proto_tree *t,
                       gboolean little_endian)
{
      guint32 res = VALUE16(tvb, *offsetp);
      proto_tree_add_uint(t, hf_x11_request_length, tvb, *offsetp, 2, res);
      *offsetp += 2;
      return res * 4;
}

static void setOfEvent(tvbuff_t *tvb, int *offsetp, proto_tree *t,
                   gboolean little_endian)
{
      BITMASK32(event);
      FLAG(event, KeyPress);
      FLAG(event, KeyRelease);
      FLAG(event, ButtonPress);
      FLAG(event, ButtonRelease);
      FLAG(event, EnterWindow);
      FLAG(event, LeaveWindow);
      FLAG(event, PointerMotion);
      FLAG(event, PointerMotionHint);
      FLAG(event, Button1Motion);
      FLAG(event, Button2Motion);
      FLAG(event, Button3Motion);
      FLAG(event, Button4Motion);
      FLAG(event, Button5Motion);
      FLAG(event, ButtonMotion);
      FLAG(event, KeymapState);
      FLAG(event, Exposure);
      FLAG(event, VisibilityChange);
      FLAG(event, StructureNotify);
      FLAG(event, ResizeRedirect);
      FLAG(event, SubstructureNotify);
      FLAG(event, SubstructureRedirect);
      FLAG(event, FocusChange);
      FLAG(event, PropertyChange);
      FLAG(event, ColormapChange);
      FLAG(event, OwnerGrabButton);
      FLAG_IF_NONZERO(event, erroneous_bits);
      ENDBITMASK;
}

static void setOfDeviceEvent(tvbuff_t *tvb, int *offsetp, proto_tree *t,
                       gboolean little_endian)
{
      BITMASK32(do_not_propagate);
      FLAG(do_not_propagate, KeyPress);
      FLAG(do_not_propagate, KeyRelease);
      FLAG(do_not_propagate, ButtonPress);
      FLAG(do_not_propagate, ButtonRelease);
      FLAG(do_not_propagate, PointerMotion);
      FLAG(do_not_propagate, Button1Motion);
      FLAG(do_not_propagate, Button2Motion);
      FLAG(do_not_propagate, Button3Motion);
      FLAG(do_not_propagate, Button4Motion);
      FLAG(do_not_propagate, Button5Motion);
      FLAG(do_not_propagate, ButtonMotion);
      FLAG_IF_NONZERO(do_not_propagate, erroneous_bits);
      ENDBITMASK;
}


static void setOfKeyButMask(tvbuff_t *tvb, int *offsetp, proto_tree *t,
                   gboolean little_endian, gboolean butmask)
{
      proto_item *ti;
      guint32 bitmask_value;
      int bitmask_offset;
      int bitmask_size;
      proto_tree *bitmask_tree;

      bitmask_value = VALUE16(tvb, *offsetp);
      bitmask_offset = *offsetp;
      bitmask_size = 2;

      if (!butmask && bitmask_value == 0x8000)
          proto_tree_add_uint_format(t, hf_x11_modifiers_mask_AnyModifier, tvb, *offsetp, 2, 0x8000,
                               "modifiers-masks: 0x8000 (AnyModifier)");
      else {
          ti = proto_tree_add_uint(t, hf_x11_modifiers_mask, tvb, *offsetp, 2,
                                     bitmask_value);
          bitmask_tree = proto_item_add_subtree(ti, ett_x11_set_of_key_mask);
          FLAG(modifiers, Shift);
          FLAG(modifiers, Lock);
          FLAG(modifiers, Control);
          FLAG(modifiers, Mod1);
          FLAG(modifiers, Mod2);
          FLAG(modifiers, Mod3);
          FLAG(modifiers, Mod4);
          FLAG(modifiers, Mod5);

          if (butmask) {
                FLAG(modifiers, Button1);
                FLAG(modifiers, Button2);
                FLAG(modifiers, Button3);
                FLAG(modifiers, Button4);
                FLAG(modifiers, Button5);
          }

          if (butmask)
                FLAG_IF_NONZERO(keybut, erroneous_bits);
          else
                FLAG_IF_NONZERO(modifiers, erroneous_bits);
      }
      *offsetp += 2;
}

static void setOfPointerEvent(tvbuff_t *tvb, int *offsetp, proto_tree *t,
                        gboolean little_endian)
{
      BITMASK16(pointer_event);
      FLAG(pointer_event, ButtonPress);
      FLAG(pointer_event, ButtonRelease);
      FLAG(pointer_event, EnterWindow);
      FLAG(pointer_event, LeaveWindow);
      FLAG(pointer_event, PointerMotion);
      FLAG(pointer_event, PointerMotionHint);
      FLAG(pointer_event, Button1Motion);
      FLAG(pointer_event, Button2Motion);
      FLAG(pointer_event, Button3Motion);
      FLAG(pointer_event, Button4Motion);
      FLAG(pointer_event, Button5Motion);
      FLAG(pointer_event, ButtonMotion);
      FLAG(pointer_event, KeymapState);
      FLAG_IF_NONZERO(pointer_event, erroneous_bits);
      ENDBITMASK;
}

static void string8(tvbuff_t *tvb, int *offsetp, proto_tree *t,
    int hf, unsigned length)
{
      const guint8 *p;
      char *s;

      p = tvb_get_ptr(tvb, *offsetp, length);
      s = g_malloc(length + 1);
      stringCopy(s, p, length);
      proto_tree_add_string(t, hf, tvb, *offsetp, length, s);
      g_free(s);
      *offsetp += length;
}

/* The length is the length of the _byte_zone_ (twice the length of the string) */

static void string16(tvbuff_t *tvb, int *offsetp, proto_tree *t, int hf,
    int hf_bytes, unsigned length, gboolean little_endian)
{
      char *s = NULL;
      unsigned l = 0;

      /*
       * In case we throw an exception, clean up whatever stuff we've
       * allocated (if any).
       */
      CLEANUP_PUSH(g_free, s);

      length += length;
      string16_with_buffer_preallocated(tvb, t, hf, hf_bytes, *offsetp, length,
                              &s, &l, little_endian);

      /*
       * Call the cleanup handler to free the string and pop the handler.
       */
      CLEANUP_CALL_AND_POP;

      *offsetp += length;
}

static void timestamp(tvbuff_t *tvb, int *offsetp, proto_tree *t, int hf,
                  gboolean little_endian)
{
      guint32 v = VALUE32(tvb, *offsetp);

      if (!v)
          proto_tree_add_uint_format(t, hf, tvb, *offsetp, 4, 0, "%s: 0 (CurrentTime)",
            proto_registrar_get_nth(hf) -> name);
      else
          proto_tree_add_uint(t, hf, tvb, *offsetp, 4, v);
      *offsetp += 4;
}

static void windowAttributes(tvbuff_t *tvb, int *offsetp, proto_tree *t,
                       gboolean little_endian)
{
      BITMASK32(window_value);
      BITFIELD(PIXMAP, window_value_mask, background_pixmap);
      BITFIELD(CARD32, window_value_mask, background_pixel);
      BITFIELD(PIXMAP, window_value_mask, border_pixmap);
      BITFIELD(CARD32, window_value_mask, border_pixel);
      BITFIELD(BITGRAVITY, window_value_mask, bit_gravity);
      BITFIELD(WINGRAVITY, window_value_mask, win_gravity);
      BITFIELD(ENUM8, window_value_mask, backing_store);
      BITFIELD(CARD32, window_value_mask, backing_planes);
      BITFIELD(CARD32, window_value_mask, backing_pixel);
      BITFIELD(BOOL,   window_value_mask, override_redirect);
      BITFIELD(BOOL,   window_value_mask, save_under);
      BITFIELD(SETofEVENT, window_value_mask, event_mask);
      BITFIELD(SETofDEVICEEVENT, window_value_mask, do_not_propagate_mask);
      BITFIELD(COLORMAP, window_value_mask, colormap);
      BITFIELD(CURSOR, window_value_mask, cursor);
      ENDBITMASK;
}

static void x11_init_protocol(void)
{
      if (x11_state_chunk != NULL)
          g_mem_chunk_destroy(x11_state_chunk);

      x11_state_chunk = g_mem_chunk_new("x11_state_chunk",
                              sizeof (x11_conv_data_t),
                              128 * sizeof (x11_conv_data_t),
                              G_ALLOC_ONLY);
}

/************************************************************************
 ***                                                                  ***
 ***         G U E S S I N G   T H E   B Y T E   O R D E R I N G      ***
 ***                                                                  ***
 ************************************************************************/

/* If we can't guess, we return TRUE (that is little_endian), cause
   I'm developing on a Linux box :-). The (non-)guess isn't cached
   however, so we may have more luck next time. I'm quite conservative
   in my assertions, cause once it's cached, it's stay in cache, and
   we may be fooled up by a packet starting with the end of a request
   started in a previous packet...
*/

static int numberOfBitSetTable[] = { 0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4 };

static int numberOfBitSet(tvbuff_t *tvb, int offset, int maskLength)
{
      int res = 0;
      while(maskLength--) {
          int c = tvb_get_guint8(tvb, offset);
          offset++;
          res += numberOfBitSetTable[c & 0xf] + numberOfBitSetTable[c >> 4];
      }
      return res;
}

static int listOfStringLengthConsistent(tvbuff_t *tvb, int offset, int length, int listLength)
{
      if (listLength > length) return FALSE;
      while(listLength--) {
          int l;
          if (!tvb_bytes_exist(tvb, offset, 1)) return TRUE;
          l = tvb_get_guint8(tvb, offset);
          if (!l) break;
          l++;
          if (l > length) return FALSE;
          if (!tvb_bytes_exist(tvb, offset, l)) return TRUE;
          offset += l;
          length -= l;
      }
      if (length > 3) return FALSE;
      return TRUE;
}

static int rounded4(int n)
{
      int remainder = n % 4;
      int res = n / 4;
      if (remainder) res++;
      return res;
}

/* We assume the order to be consistent, until proven wrong. */

static gboolean consistentWithOrder(int length, tvbuff_t *tvb, int offset, guint16 (*v16)(tvbuff_t *, gint))
{
      switch(tvb_get_guint8(tvb, offset)) {
        case X_CreateWindow:
          return !tvb_bytes_exist(tvb, offset, 32) || length == 8 + numberOfBitSet(tvb, offset + 7 * 4, 4);

        case X_ChangeWindowAttributes:
        case X_ChangeGC:
          return !tvb_bytes_exist(tvb, offset, 12) || length == 3 + numberOfBitSet(tvb, offset + 8, 4);

        case X_GetWindowAttributes:
        case X_DestroyWindow:
        case X_DestroySubwindows:
        case X_ChangeSaveSet:
        case X_MapWindow:
        case X_MapSubwindows:
        case X_UnmapWindow:
        case X_UnmapSubwindows:
        case X_CirculateWindow:
        case X_GetGeometry:
        case X_QueryTree:
        case X_GetAtomName:
        case X_ListProperties:
        case X_GetSelectionOwner:
        case X_UngrabPointer:
        case X_UngrabKeyboard:
        case X_AllowEvents:
        case X_QueryPointer:
        case X_CloseFont:
        case X_QueryFont:
        case X_FreePixmap:
        case X_FreeGC:
        case X_FreeColormap:
        case X_InstallColormap:
        case X_UninstallColormap:
        case X_ListInstalledColormaps:
        case X_FreeCursor:
        case X_GetKeyboardMapping:
        case X_KillClient:
          return length == 2;

        case X_ReparentWindow:
        case X_SetSelectionOwner:
        case X_ChangeActivePointerGrab:
        case X_GrabKeyboard:
        case X_GrabKey:
        case X_GetMotionEvents:
        case X_TranslateCoords:
        case X_CreatePixmap:
        case X_CopyGC:
        case X_ClearArea:
        case X_CreateColormap:
        case X_AllocColor:
        case X_AllocColorPlanes:
          return length == 4;

        case X_ConfigureWindow:
          return !tvb_bytes_exist(tvb, offset, 10) || length == 3 + numberOfBitSet(tvb, offset + 8, 2);

        case X_InternAtom:
        case X_QueryExtension:
          return !tvb_bytes_exist(tvb, offset, 6) || length == 2 + rounded4(v16(tvb, offset + 4));

        case X_ChangeProperty:
          {
              int multiplier, type;
              if (!tvb_bytes_exist(tvb, offset, 17)) return TRUE;
              type = tvb_get_guint8(tvb, 16);
              if (type != 8 && type != 16 && type != 32) return FALSE;
              multiplier = type == 8 ? 1 : type == 16 ? 2 : 4;
              if (!tvb_bytes_exist(tvb, offset, 24)) return TRUE;
              return length == 6 + rounded4((v16 == tvb_get_letohs ? tvb_get_letohl : tvb_get_ntohl)(tvb, offset + 20) * multiplier);
          }

        case X_DeleteProperty:
        case X_UngrabButton:
        case X_UngrabKey:
        case X_SetInputFocus:
        case X_CopyColormapAndFree:
        case X_AllocColorCells:
        case X_QueryBestSize:
        case X_ChangePointerControl:
        case X_SetScreenSaver:
          return length == 3;

        case X_GetProperty:
        case X_ConvertSelection:
        case X_GrabPointer:
        case X_GrabButton:
        case X_WarpPointer:
          return length == 6;

        case X_SendEvent:
          return length == 11;

        case X_GrabServer:
        case X_UngrabServer:
        case X_GetInputFocus:
        case X_QueryKeymap:
        case X_GetFontPath:
        case X_ListExtensions:
        case X_GetKeyboardControl:
        case X_Bell:
        case X_GetPointerControl:
        case X_GetScreenSaver:
        case X_ListHosts:
        case X_SetAccessControl:
        case X_SetCloseDownMode:
        case X_ForceScreenSaver:
        case X_GetPointerMapping:
        case X_GetModifierMapping:
          return length == 1;

        case X_OpenFont:
        case X_AllocNamedColor:
        case X_LookupColor:
          return !tvb_bytes_exist(tvb, offset, 10) || length == 3 + rounded4(v16(tvb, offset + 8));

        case X_QueryTextExtents:
          return length >= 2;

        case X_ListFonts:
        case X_ListFontsWithInfo:
        case X_ChangeHosts:
          return !tvb_bytes_exist(tvb, offset, 8) || length == 2 + rounded4(v16(tvb, offset + 6));

        case X_SetFontPath:
          if (length < 2) return FALSE;
          if (!tvb_bytes_exist(tvb, offset, 8)) return TRUE;
          return listOfStringLengthConsistent(tvb, offset + 8, (length - 2) * 4, v16(tvb, offset + 4));

        case X_CreateGC:
          return !tvb_bytes_exist(tvb, offset, 16) || length == 4 + numberOfBitSet(tvb, offset + 12, 4);

        case X_SetDashes:
          return !tvb_bytes_exist(tvb, offset, 12) || length == 3 + rounded4(v16(tvb, offset + 10));

        case X_SetClipRectangles:
        case X_PolySegment:
        case X_PolyRectangle:
        case X_PolyFillRectangle:
          return length >= 3 && (length - 3) % 2 == 0;

        case X_CopyArea:
          return length == 7;

        case X_CopyPlane:
        case X_CreateCursor:
        case X_CreateGlyphCursor:
          return length == 8;

        case X_PolyPoint:
        case X_PolyLine:
        case X_FreeColors:
          return length >= 3;

        case X_PolyArc:
        case X_PolyFillArc:
          return length >= 3 && (length - 3) % 3 == 0;

        case X_FillPoly:
        case X_ImageText8:
          return length >= 4;

        case X_PutImage:
          return length >= 6;

        case X_GetImage:
        case X_RecolorCursor:
          return length == 5;

        case X_PolyText8:
          if (length < 4) return FALSE;
          return TRUE; /* We don't perform many controls on this one */

        case X_PolyText16:
          if (length < 4) return FALSE;
          return TRUE; /* We don't perform many controls on this one */

        case X_ImageText16:
          return length >= 4;

        case X_StoreColors:
          return length > 2 && (length - 2) % 3 == 0;

        case X_StoreNamedColor:
          return !tvb_bytes_exist(tvb, offset, 14) || length == 4 + rounded4(v16(tvb, offset + 12));

        case X_QueryColors:
          return length >= 2;

        case X_ChangeKeyboardMapping:
          return !tvb_bytes_exist(tvb, offset, 6) || length == 2 + tvb_get_guint8(tvb, 1) * tvb_get_guint8(tvb, 5);

        case X_ChangeKeyboardControl:
          return !tvb_bytes_exist(tvb, offset, 6) || length == 2 + numberOfBitSet(tvb, offset + 4, 2);

        case X_RotateProperties:
          return !tvb_bytes_exist(tvb, offset, 10) || length == 3 + v16(tvb, offset + 8);

        case X_SetPointerMapping:
          return length == 1 + rounded4(tvb_get_guint8(tvb, 1));

        case X_SetModifierMapping:
          return length == 1 + tvb_get_guint8(tvb, 1) * 2;

        case X_NoOperation:
          return length >= 1;

        default:
          return TRUE;
      }
}

/* -1 means doesn't match, +1 means match, 0 means don't know */

static int x_endian_match(tvbuff_t *tvb, guint16 (*v16)(tvbuff_t *, gint))
{
      int offset, nextoffset;
      int atLeastOne = 0;

      for(offset = 0; tvb_bytes_exist(tvb, offset, 4); offset = nextoffset) {
          int length;
          length = v16(tvb, offset + 2);
          if (!length) return -1;
          nextoffset = offset + length * 4;
          if (!consistentWithOrder(length, tvb, offset, v16)) return -1;
          atLeastOne = 1;
      }
      return atLeastOne;
}

static gboolean
guess_byte_ordering(tvbuff_t *tvb, packet_info *pinfo,
                x11_conv_data_t *state)
{
      /* With X the client gives the byte ordering for the protocol,
       and the port on the server tells us we're speaking X. */

      int le, be, decision, decisionToCache;

      if (state->byte_order == BYTE_ORDER_BE)
          return FALSE; /* known to be big-endian */
      else if (state->byte_order == BYTE_ORDER_LE)
          return TRUE;  /* known to be little-endian */

      if (pinfo->srcport == pinfo->match_port) {
                /*
                 * This is a reply or event; we don't try to guess the
                 * byte order on it for now.
                 */
          return TRUE;
      }

      le = x_endian_match(tvb, tvb_get_letohs);
      be = x_endian_match(tvb, tvb_get_ntohs);

      /* remember that "decision" really means "little_endian". */
      if (le == be) {
          /* We have no reason to believe it's little- rather than
             big-endian, so we guess the shortest length is the
             right one.
          */
          if (!tvb_bytes_exist(tvb, 0, 4))
              /* Not even a way to get the length. We're biased
                 toward little endianness here (essentially the
                 x86 world right now). Decoding won't go very far
                 anyway.
              */
              decision = TRUE;
          else
              decision = tvb_get_letohs(tvb, 2) <= tvb_get_ntohs(tvb, 2);
      } else
        decision = le >= be;

      decisionToCache = (le < 0 && be > 0) || (le > 0 && be < 0);
      if (decisionToCache) {
          /*
           * Remember the decision.
           */
          state->byte_order = decision ? BYTE_ORDER_LE : BYTE_ORDER_BE;
      }

      /*
      fprintf(stderr, "packet %d\tle %d\tbe %d\tlittle_endian %d\tcache %d\n",
            pinfo->fd -> num, le, be, decision, decisionToCache);
      */
      return decision;
}

/************************************************************************
 ***                                                                  ***
 ***              D E C O D I N G   O N E   P A C K E T               ***
 ***                                                                  ***
 ************************************************************************/

/*
 * Decode an initial connection request.
 */
static void dissect_x11_initial_conn(tvbuff_t *tvb, packet_info *pinfo,
    proto_tree *tree, x11_conv_data_t *state, gboolean little_endian)
{
      int offset = 0;
      int *offsetp = &offset;
      proto_item *ti;
      proto_tree *t;
      guint16 auth_proto_name_length, auth_proto_data_length;
      gint left;

      ti = proto_tree_add_item(tree, proto_x11, tvb, 0, -1, FALSE);
      proto_item_append_text(ti, ", Request, Initial connection request");
      t = proto_item_add_subtree(ti, ett_x11);

      CARD8(byte_order);
      UNUSED(1);
      CARD16(protocol_major_version);
      CARD16(protocol_minor_version);
      auth_proto_name_length = CARD16(authorization_protocol_name_length);
      auth_proto_data_length = CARD16(authorization_protocol_data_length);
      UNUSED(2);

      if (auth_proto_name_length != 0) {
          STRING8(authorization_protocol_name, auth_proto_name_length);
          offset = ROUND_LENGTH(offset);
      }

      if (auth_proto_data_length != 0) {
          STRING8(authorization_protocol_data, auth_proto_data_length);
          offset = ROUND_LENGTH(offset);
      }

      if ((left = tvb_reported_length_remaining(tvb, offset)) > 0)
            proto_tree_add_item(t, hf_x11_undecoded, tvb, offset, left,
            little_endian);

      /*
       * This is the initial connection request...
       */
      state->iconn_frame = pinfo->fd->num;

      /*
       * ...and we're expecting a reply to it.
       */
      state->sequencenumber = 0;
      g_hash_table_insert(state->seqtable, GINT_TO_POINTER(state->sequencenumber),
                    (int *)INITIAL_CONN);
}

static void dissect_x11_initial_reply(tvbuff_t *tvb, packet_info *pinfo,
    proto_tree *tree, const char _U_ *sep, x11_conv_data_t *volatile state,
    gboolean little_endian)
{
            int offset = 0, *offsetp = &offset, left;
      unsigned char success;
      int length_of_vendor;
      int length_of_reason;
      proto_item *ti;
      proto_tree *t;

      ti = proto_tree_add_item(tree, proto_x11, tvb, 0, -1, FALSE);
      proto_item_append_text(ti, ", Reply, Initial connection reply");
      t = proto_item_add_subtree(ti, ett_x11);

      state->iconn_reply = pinfo->fd->num;
      success = INT8(success);
      if (success) {
            UNUSED(1);
            length_of_reason = 0;
      }
      else {
            length_of_reason = INT8(length_of_reason);
      }

      INT16(protocol_major_version);
      INT16(protocol_minor_version);
      INT16(replylength);
      if (success) {
            INT32(release_number);
            INT32(resource_id_base);
            INT32(resource_id_mask);
            INT32(motion_buffer_size);
            length_of_vendor = INT16(length_of_vendor);
            INT16(maximum_request_length);
            INT8(number_of_screens_in_roots);
            INT8(number_of_formats_in_pixmap_formats);
            INT8(image_byte_order);
            INT8(bitmap_format_bit_order);
            INT8(bitmap_format_scanline_unit);
            INT8(bitmap_format_scanline_pad);
            INT8(min_keycode);
            INT8(max_keycode);
            UNUSED(4);
            STRING8(vendor, length_of_vendor);
      } else {
            STRING8(reason, length_of_reason);
      }

            if ((left = tvb_reported_length_remaining(tvb, offset)) > 0)
          UNDECODED(left);

}

static void dissect_x11_request(tvbuff_t *tvb, packet_info *pinfo,
    proto_tree *tree, const char *sep, x11_conv_data_t *state,
    gboolean little_endian)
{
      int offset = 0;
      int *offsetp = &offset;
      int next_offset;
      proto_item *ti;
      proto_tree *t;
      int length, opcode, i;
      guint8 v8, v8_2, v8_3;
      guint16 v16;
      guint32 v32;
      gint left;
      gchar *name;

      length = VALUE16(tvb, 2) * 4;

      if (length < 4) {
          /* Bogus message length? */
          return;
      }

      next_offset = offset + length;

      ti = proto_tree_add_item(tree, proto_x11, tvb, 0, -1, FALSE);
      t = proto_item_add_subtree(ti, ett_x11);

      if (PACKET_IS_NEW(pinfo))
            ++state->sequencenumber;

      OPCODE();

      if (check_col(pinfo->cinfo, COL_INFO))
        col_append_fstr(pinfo->cinfo, COL_INFO, "%s %s", sep,
                    val_to_str(opcode, state->opcode_vals, 
                             "<Unknown opcode %d>"));

      proto_item_append_text(ti, ", Request, opcode: %d (%s)", 
                       opcode, val_to_str(opcode, state->opcode_vals,
                                    "<Unknown opcode %d>"));

      /*
       * Does this request expect a reply?
       */
      switch(opcode) {

      case X_QueryExtension:

            /* necessary processing even if tree == NULL */

            v16 = VALUE16(tvb, 4);
            name = g_malloc(v16 + 1);
            stringCopy(name, tvb_get_ptr(tvb, 8, v16), v16);

            /* store string of extension, opcode will be set at reply */
            i = 0;
            while(i < MAX_OPCODES) {
                  if (state->opcode_vals[i].strptr == NULL) {
                        state->opcode_vals[i].strptr = name;
                        g_hash_table_insert(state->valtable,
                                        GINT_TO_POINTER(state->sequencenumber), 
                                        (int *)&state->opcode_vals[i]);
                        break;
                  } else if (strcmp(state->opcode_vals[i].strptr,
                                name) == 0) {
                        g_hash_table_insert(state->valtable,
                                        GINT_TO_POINTER(state->sequencenumber), 
                                        (int *)&state->opcode_vals[i]);
                        break;
                  }
                  i++;
            }

            /* QueryExtension expects a reply, fall through */

      case X_AllocColor:
      case X_AllocColorCells:
      case X_AllocColorPlanes:
      case X_AllocNamedColor:
      case X_GetAtomName:
      case X_GetFontPath:
      case X_GetGeometry:
      case X_GetImage:
      case X_GetInputFocus:
      case X_GetKeyboardControl:
      case X_GetKeyboardMapping:
      case X_GetModifierMapping:
      case X_GetMotionEvents:
      case X_GetPointerControl:
      case X_GetPointerMapping:
      case X_GetProperty:
      case X_GetScreenSaver:
      case X_GetSelectionOwner:
      case X_GetWindowAttributes:
      case X_GrabKeyboard:
      case X_GrabPointer:
      case X_InternAtom:
      case X_ListExtensions:
      case X_ListFonts:
      case X_ListFontsWithInfo:
      case X_ListHosts:
      case X_ListInstalledColormaps:
      case X_ListProperties:
      case X_LookupColor:
      case X_QueryBestSize:
      case X_QueryColors:
      case X_QueryFont:
      case X_QueryKeymap:
      case X_QueryPointer:
      case X_QueryTextExtents:
      case X_QueryTree:
      case X_SetModifierMapping:
      case X_SetPointerMapping:
      case X_TranslateCoords:
            /*
             * Those requests expect a reply.
             */
            g_hash_table_insert(state->seqtable,
                            GINT_TO_POINTER(state->sequencenumber), 
                            GINT_TO_POINTER(opcode));

            break;

      default:
            /* 
             * With Extension, we don't know, so assume there could be one
             */
            if (opcode >= X_FirstExtension && opcode <= X_LastExtension) {
                  g_hash_table_insert(state->seqtable,
                                  GINT_TO_POINTER(state->sequencenumber), 
                                  GINT_TO_POINTER(opcode));
            }

            /*
             * No reply is expected from any other request.
             */
            break;
      }

      if (tree == NULL)
       return; 

      switch(opcode) {

      case X_CreateWindow:
          CARD8(depth);
          REQUEST_LENGTH();
          WINDOW(wid);
          WINDOW(parent);
          INT16(x);
          INT16(y);
          CARD16(width);
          CARD16(height);
          CARD16(border_width);
          ENUM16(window_class);
          VISUALID(visual);
          windowAttributes(tvb, offsetp, t, little_endian);
          break;

      case X_ChangeWindowAttributes:
          UNUSED(1);
          REQUEST_LENGTH();
          WINDOW(window);
          windowAttributes(tvb, offsetp, t, little_endian);
          break;

      case X_GetWindowAttributes:
      case X_DestroyWindow:
      case X_DestroySubwindows:
          UNUSED(1);
          REQUEST_LENGTH();
          WINDOW(window);
          break;

      case X_ChangeSaveSet:
          ENUM8(save_set_mode);
          REQUEST_LENGTH();
          WINDOW(window);
          break;

      case X_ReparentWindow:
          UNUSED(1);
          REQUEST_LENGTH();
          WINDOW(window);
          WINDOW(parent);
          INT16(x);
          INT16(y);
          break;

      case X_MapWindow:
      case X_MapSubwindows:
      case X_UnmapWindow:
      case X_UnmapSubwindows:
          UNUSED(1);
          REQUEST_LENGTH();
          WINDOW(window);
          break;

      case X_ConfigureWindow:
          UNUSED(1);
          REQUEST_LENGTH();
          WINDOW(window);
          BITMASK16(configure_window);
          UNUSED(2);
          BITFIELD(INT16,  configure_window_mask, x);
          BITFIELD(INT16,  configure_window_mask, y);
          BITFIELD(CARD16, configure_window_mask, width);
          BITFIELD(CARD16, configure_window_mask, height);
          BITFIELD(CARD16, configure_window_mask, border_width);
          BITFIELD(WINDOW, configure_window_mask, sibling);
          BITFIELD(ENUM8,  configure_window_mask, stack_mode);
          ENDBITMASK;
          PAD();
          break;

      case X_CirculateWindow:
          ENUM8(direction);
          REQUEST_LENGTH();
          WINDOW(window);
          break;

      case X_GetGeometry:
      case X_QueryTree:
          UNUSED(1);
          REQUEST_LENGTH();
          DRAWABLE(drawable);
          break;

      case X_InternAtom:
          BOOL(only_if_exists);
          REQUEST_LENGTH();
          v16 = FIELD16(name_length);
          UNUSED(2);
          STRING8(name, v16);
          PAD();
          break;

      case X_GetAtomName:
          UNUSED(1);
          REQUEST_LENGTH();
          ATOM(atom);
          break;

      case X_ChangeProperty:
          ENUM8(mode);
          REQUEST_LENGTH();
          WINDOW(window);
          ATOM(property);
          ATOM(type);
          CARD8(format);
          UNUSED(3);
          v32 = CARD32(data_length);
          LISTofBYTE(data, v32);
          PAD();
          break;

      case X_DeleteProperty:
          UNUSED(1);
          REQUEST_LENGTH();
          WINDOW(window);
          ATOM(property);
          break;

      case X_GetProperty:
          BOOL(delete);
          REQUEST_LENGTH();
          WINDOW(window);
          ATOM(property);
          ATOM(get_property_type);
          CARD32(long_offset);
          CARD32(long_length);
          break;

      case X_ListProperties:
          UNUSED(1);
          REQUEST_LENGTH();
          WINDOW(window);
          break;

      case X_SetSelectionOwner:
          UNUSED(1);
          REQUEST_LENGTH();
          WINDOW(owner);
          ATOM(selection);
          TIMESTAMP(time);
          break;

      case X_GetSelectionOwner:
          UNUSED(1);
          REQUEST_LENGTH();
          ATOM(selection);
          break;

      case X_ConvertSelection:
          UNUSED(1);
          REQUEST_LENGTH();
          WINDOW(requestor);
          ATOM(selection);
          ATOM(target);
          ATOM(property);
          TIMESTAMP(time);
          break;

      case X_SendEvent:
          BOOL(propagate);
          REQUEST_LENGTH();
          WINDOW(destination);
          SETofEVENT(event_mask);
          UNDECODED(32);
          break;

      case X_GrabPointer:
          BOOL(owner_events);
          REQUEST_LENGTH();
          WINDOW(grab_window);
          SETofPOINTEREVENT(pointer_event_mask);
          ENUM8(pointer_mode);
          ENUM8(keyboard_mode);
          WINDOW(confine_to);
          CURSOR(cursor);
          TIMESTAMP(time);
          break;

      case X_UngrabPointer:
          UNUSED(1);
          REQUEST_LENGTH();
          TIMESTAMP(time);
          break;

      case X_GrabButton:
          BOOL(owner_events);
          REQUEST_LENGTH();
          WINDOW(grab_window);
          SETofPOINTEREVENT(event_mask);
          ENUM8(pointer_mode);
          ENUM8(keyboard_mode);
          WINDOW(confine_to);
          CURSOR(cursor);
          BUTTON(button);
          UNUSED(1);
          SETofKEYMASK(modifiers);
          break;

      case X_UngrabButton:
          BUTTON(button);
          REQUEST_LENGTH();
          WINDOW(grab_window);
          SETofKEYMASK(modifiers);
          UNUSED(2);
          break;

      case X_ChangeActivePointerGrab:
          UNUSED(1);
          REQUEST_LENGTH();
          CURSOR(cursor);
          TIMESTAMP(time);
          SETofPOINTEREVENT(event_mask);
          UNUSED(2);
          break;

      case X_GrabKeyboard:
          BOOL(owner_events);
          REQUEST_LENGTH();
          WINDOW(grab_window);
          TIMESTAMP(time);
          ENUM8(pointer_mode);
          ENUM8(keyboard_mode);
          UNUSED(2);
          break;

      case X_UngrabKeyboard:
          UNUSED(1);
          REQUEST_LENGTH();
          TIMESTAMP(time);
          break;

      case X_GrabKey:
          BOOL(owner_events);
          REQUEST_LENGTH();
          WINDOW(grab_window);
          SETofKEYMASK(modifiers);
          KEYCODE(key);
          ENUM8(pointer_mode);
          ENUM8(keyboard_mode);
          UNUSED(3);
          break;

      case X_UngrabKey:
          KEYCODE(key);
          REQUEST_LENGTH();
          WINDOW(grab_window);
          SETofKEYMASK(modifiers);
          UNUSED(2);
          break;

      case X_AllowEvents:
          ENUM8(allow_events_mode);
          REQUEST_LENGTH();
          TIMESTAMP(time);
          break;

      case X_GrabServer:
          UNUSED(1);
          REQUEST_LENGTH();
          break;

      case X_UngrabServer:
          UNUSED(1);
          REQUEST_LENGTH();
          break;

      case X_QueryPointer:
          UNUSED(1);
          REQUEST_LENGTH();
          WINDOW(window);
          break;

      case X_GetMotionEvents:
          UNUSED(1);
          REQUEST_LENGTH();
          WINDOW(window);
          TIMESTAMP(start);
          TIMESTAMP(stop);
          break;

      case X_TranslateCoords:
          UNUSED(1);
          REQUEST_LENGTH();
          WINDOW(src_window);
          WINDOW(dst_window);
          INT16(src_x);
          INT16(src_y);
          break;

      case X_WarpPointer:
          UNUSED(1);
          REQUEST_LENGTH();
          WINDOW(warp_pointer_src_window);
          WINDOW(warp_pointer_dst_window);
          INT16(src_x);
          INT16(src_y);
          CARD16(src_width);
          CARD16(src_height);
          INT16(dst_x);
          INT16(dst_y);
          break;

      case X_SetInputFocus:
          ENUM8(revert_to);
          REQUEST_LENGTH();
          WINDOW(focus);
          TIMESTAMP(time);
          break;

      case X_GetInputFocus:
          UNUSED(1);
          REQUEST_LENGTH();
          break;

      case X_QueryKeymap:
          UNUSED(1);
          REQUEST_LENGTH();
          break;

      case X_OpenFont:
          UNUSED(1);
          REQUEST_LENGTH();
          FONT(fid);
          v16 = FIELD16(name_length);
          UNUSED(2);
          STRING8(name, v16);
          PAD();
          break;

      case X_CloseFont:
          UNUSED(1);
          REQUEST_LENGTH();
          FONT(font);
          break;

      case X_QueryFont:
          UNUSED(1);
          REQUEST_LENGTH();
          FONTABLE(font);
          break;

      case X_QueryTextExtents:
          v8 = BOOL(odd_length);
          REQUEST_LENGTH();
          FONTABLE(font);
          STRING16(string16, (next_offset - offset - (v8 ? 2 : 0)) / 2);
          PAD();
          break;

      case X_ListFonts:
          UNUSED(1);
          REQUEST_LENGTH();
          CARD16(max_names);
          v16 = FIELD16(pattern_length);
          STRING8(pattern, v16);
          PAD();
          break;

      case X_ListFontsWithInfo:
          UNUSED(1);
          REQUEST_LENGTH();
          CARD16(max_names);
          v16 = FIELD16(pattern_length);
          STRING8(pattern, v16);
          PAD();
          break;

      case X_SetFontPath:
          UNUSED(1);
          REQUEST_LENGTH();
          v16 = CARD16(str_number_in_path);
          UNUSED(2);
          LISTofSTRING8(path, v16);
          PAD();
          break;

      case X_GetFontPath:
          UNUSED(1);
          REQUEST_LENGTH();
          break;

      case X_CreatePixmap:
          CARD8(depth);
          REQUEST_LENGTH();
          PIXMAP(pid);
          DRAWABLE(drawable);
          CARD16(width);
          CARD16(height);
          break;

      case X_FreePixmap:
          UNUSED(1);
          REQUEST_LENGTH();
          PIXMAP(pixmap);
          break;

      case X_CreateGC:
          UNUSED(1);
          REQUEST_LENGTH();
          GCONTEXT(cid);
          DRAWABLE(drawable);
          gcAttributes(tvb, offsetp, t, little_endian);
          break;

      case X_ChangeGC:
          UNUSED(1);
          REQUEST_LENGTH();
          GCONTEXT(gc);
          gcAttributes(tvb, offsetp, t, little_endian);
          break;

      case X_CopyGC:
          UNUSED(1);
          REQUEST_LENGTH();
          GCONTEXT(src_gc);
          GCONTEXT(dst_gc);
          gcMask(tvb, offsetp, t, little_endian);
          break;

      case X_SetDashes:
          UNUSED(1);
          REQUEST_LENGTH();
          GCONTEXT(gc);
          CARD16(dash_offset);
          v16 = FIELD16(dashes_length);
          LISTofCARD8(dashes, v16);
          PAD();
          break;

      case X_SetClipRectangles:
          ENUM8(ordering);
          REQUEST_LENGTH();
          GCONTEXT(gc);
          INT16(clip_x_origin);
          INT16(clip_y_origin);
          LISTofRECTANGLE(rectangles);
          break;

      case X_FreeGC:
          UNUSED(1);
          REQUEST_LENGTH();
          GCONTEXT(gc);
          break;

      case X_ClearArea:
          BOOL(exposures);
          REQUEST_LENGTH();
          WINDOW(window);
          INT16(x);
          INT16(y);
          CARD16(width);
          CARD16(height);
          break;

      case X_CopyArea:
          UNUSED(1);
          REQUEST_LENGTH();
          DRAWABLE(src_drawable);
          DRAWABLE(dst_drawable);
          GCONTEXT(gc);
          INT16(src_x);
          INT16(src_y);
          INT16(dst_x);
          INT16(dst_y);
          CARD16(width);
          CARD16(height);
          break;

      case X_CopyPlane:
          UNUSED(1);
          REQUEST_LENGTH();
          DRAWABLE(src_drawable);
          DRAWABLE(dst_drawable);
          GCONTEXT(gc);
          INT16(src_x);
          INT16(src_y);
          INT16(dst_x);
          INT16(dst_y);
          CARD16(width);
          CARD16(height);
          CARD32(bit_plane);
          break;

      case X_PolyPoint:
          ENUM8(coordinate_mode);
          v16 = REQUEST_LENGTH();
          DRAWABLE(drawable);
          GCONTEXT(gc);
          LISTofPOINT(points, v16 - 12);
          break;

      case X_PolyLine:
          ENUM8(coordinate_mode);
          v16 = REQUEST_LENGTH();
          DRAWABLE(drawable);
          GCONTEXT(gc);
          LISTofPOINT(points, v16 - 12);
          break;

      case X_PolySegment:
          UNUSED(1);
          REQUEST_LENGTH();
          DRAWABLE(drawable);
          GCONTEXT(gc);
          LISTofSEGMENT(segments);
          break;

      case X_PolyRectangle:
          UNUSED(1);
          REQUEST_LENGTH();
          DRAWABLE(drawable);
          GCONTEXT(gc);
          LISTofRECTANGLE(rectangles);
          break;

      case X_PolyArc:
          UNUSED(1);
          REQUEST_LENGTH();
          DRAWABLE(drawable);
          GCONTEXT(gc);
          LISTofARC(arcs);
          break;

      case X_FillPoly:
          UNUSED(1);
          v16 = REQUEST_LENGTH();
          DRAWABLE(drawable);
          GCONTEXT(gc);
          ENUM8(shape);
          ENUM8(coordinate_mode);
          UNUSED(2);
          LISTofPOINT(points, v16 - 16);
          break;

      case X_PolyFillRectangle:
          UNUSED(1);
          REQUEST_LENGTH();
          DRAWABLE(drawable);
          GCONTEXT(gc);
          LISTofRECTANGLE(rectangles);
          break;

      case X_PolyFillArc:
          UNUSED(1);
          REQUEST_LENGTH();
          DRAWABLE(drawable);
          GCONTEXT(gc);
          LISTofARC(arcs);
          break;

      case X_PutImage:
          ENUM8(image_format);
          v16 = REQUEST_LENGTH();
          DRAWABLE(drawable);
          GCONTEXT(gc);
          CARD16(width);
          CARD16(height);
          INT16(dst_x);
          INT16(dst_y);
          CARD8(left_pad);
          CARD8(depth);
          UNUSED(2);
          LISTofBYTE(data, v16 - 24);
          PAD();
          break;

      case X_GetImage:
          ENUM8(image_pixmap_format);
          REQUEST_LENGTH();
          DRAWABLE(drawable);
          INT16(x);
          INT16(y);
          CARD16(width);
          CARD16(height);
          CARD32(plane_mask);
          break;

      case X_PolyText8:
          UNUSED(1);
          v16 = REQUEST_LENGTH();
          DRAWABLE(drawable);
          GCONTEXT(gc);
          INT16(x);
          INT16(y);
          LISTofTEXTITEM8(items);
          PAD();
          break;

      case X_PolyText16:
          UNUSED(1);
          v16 = REQUEST_LENGTH();
          DRAWABLE(drawable);
          GCONTEXT(gc);
          INT16(x);
          INT16(y);
          LISTofTEXTITEM16(items);
          PAD();
          break;

      case X_ImageText8:
          v8 = FIELD8(string_length);
          REQUEST_LENGTH();
          DRAWABLE(drawable);
          GCONTEXT(gc);
          INT16(x);
          INT16(y);
          STRING8(string, v8);
          PAD();
          break;

      case X_ImageText16:
          v8 = FIELD8(string_length);
          REQUEST_LENGTH();
          DRAWABLE(drawable);
          GCONTEXT(gc);
          INT16(x);
          INT16(y);
          STRING16(string16, v8);
          PAD();
          break;

      case X_CreateColormap:
          ENUM8(alloc);
          REQUEST_LENGTH();
          COLORMAP(mid);
          WINDOW(window);
          VISUALID(visual);
          break;

      case X_FreeColormap:
          UNUSED(1);
          REQUEST_LENGTH();
          COLORMAP(cmap);
          break;

      case X_CopyColormapAndFree:
          UNUSED(1);
          REQUEST_LENGTH();
          COLORMAP(mid);
          COLORMAP(src_cmap);
          break;

      case X_InstallColormap:
          UNUSED(1);
          REQUEST_LENGTH();
          COLORMAP(cmap);
          break;

      case X_UninstallColormap:
          UNUSED(1);
          REQUEST_LENGTH();
          COLORMAP(cmap);
          break;

      case X_ListInstalledColormaps:
          UNUSED(1);
          REQUEST_LENGTH();
          WINDOW(window);
          break;

      case X_AllocColor:
          UNUSED(1);
          REQUEST_LENGTH();
          COLORMAP(cmap);
          CARD16(red);
          CARD16(green);
          CARD16(blue);
          UNUSED(2);
          break;

      case X_AllocNamedColor:
          UNUSED(1);
          REQUEST_LENGTH();
          COLORMAP(cmap);
          v16 = FIELD16(name_length);
          UNUSED(2);
          STRING8(name, v16);
          PAD();
          break;

      case X_AllocColorCells:
          BOOL(contiguous);
          REQUEST_LENGTH();
          COLORMAP(cmap);
          CARD16(colors);
          CARD16(planes);
          break;

      case X_AllocColorPlanes:
          BOOL(contiguous);
          REQUEST_LENGTH();
          COLORMAP(cmap);
          CARD16(colors);
          CARD16(reds);
          CARD16(greens);
          CARD16(blues);
          break;

      case X_FreeColors:
          UNUSED(1);
          v16 = REQUEST_LENGTH();
          COLORMAP(cmap);
          CARD32(plane_mask);
          LISTofCARD32(pixels, v16 - 12);
          break;

      case X_StoreColors:
          UNUSED(1);
          v16 = REQUEST_LENGTH();
          COLORMAP(cmap);
          LISTofCOLORITEM(color_items, v16 - 8);
          break;

      case X_StoreNamedColor:
          COLOR_FLAGS(color);
          REQUEST_LENGTH();
          COLORMAP(cmap);
          CARD32(pixel);
          v16 = FIELD16(name_length);
          UNUSED(2);
          STRING8(name, v16);
          PAD();
          break;

      case X_QueryColors:
          UNUSED(1);
          v16 = REQUEST_LENGTH();
          COLORMAP(cmap);
          LISTofCARD32(pixels, v16 - 8);
          break;

      case X_LookupColor:
          UNUSED(1);
          REQUEST_LENGTH();
          COLORMAP(cmap);
          v16 = FIELD16(name_length);
          UNUSED(2);
          STRING8(name, v16);
          PAD();
          break;

      case X_CreateCursor:
          UNUSED(1);
          REQUEST_LENGTH();
          CURSOR(cid);
          PIXMAP(source_pixmap);
          PIXMAP(mask);
          CARD16(fore_red);
          CARD16(fore_green);
          CARD16(fore_blue);
          CARD16(back_red);
          CARD16(back_green);
          CARD16(back_blue);
          CARD16(x);
          CARD16(y);
          break;

      case X_CreateGlyphCursor:
          UNUSED(1);
          REQUEST_LENGTH();
          CURSOR(cid);
          FONT(source_font);
          FONT(mask_font);
          CARD16(source_char);
          CARD16(mask_char);
          CARD16(fore_red);
          CARD16(fore_green);
          CARD16(fore_blue);
          CARD16(back_red);
          CARD16(back_green);
          CARD16(back_blue);
          break;

      case X_FreeCursor:
          UNUSED(1);
          REQUEST_LENGTH();
          CURSOR(cursor);
          break;

      case X_RecolorCursor:
          UNUSED(1);
          REQUEST_LENGTH();
          CURSOR(cursor);
          CARD16(fore_red);
          CARD16(fore_green);
          CARD16(fore_blue);
          CARD16(back_red);
          CARD16(back_green);
          CARD16(back_blue);
          break;

      case X_QueryBestSize:
          ENUM8(class);
          REQUEST_LENGTH();
          DRAWABLE(drawable);
          CARD16(width);
          CARD16(height);
          break;

      case X_QueryExtension:
          UNUSED(1);
          REQUEST_LENGTH();
          v16 = FIELD16(name_length);
          UNUSED(2);
          STRING8(name, v16);
          PAD();
          break;

      case X_ListExtensions:
          UNUSED(1);
          REQUEST_LENGTH();
          break;

      case X_ChangeKeyboardMapping:
          v8 = FIELD8(keycode_count);
          REQUEST_LENGTH();
          v8_2 = KEYCODE(first_keycode);
          v8_3 = FIELD8(keysyms_per_keycode);
          UNUSED(2);
          LISTofKEYSYM(keysyms, state->keycodemap, v8_2, v8, v8_3);
          break;

      case X_GetKeyboardMapping:
          UNUSED(1);
          REQUEST_LENGTH();
          state->request.GetKeyboardMapping.first_keycode
          = KEYCODE(first_keycode);
          FIELD8(count);
          UNUSED(2);
          break;

      case X_ChangeKeyboardControl:
          UNUSED(1);
          REQUEST_LENGTH();
          BITMASK32(keyboard_value);
          BITFIELD(INT8, keyboard_value_mask, key_click_percent);
          BITFIELD(INT8, keyboard_value_mask, bell_percent);
          BITFIELD(INT16, keyboard_value_mask, bell_pitch);
          BITFIELD(INT16, keyboard_value_mask, bell_duration);
          BITFIELD(INT16, keyboard_value_mask, led);
          BITFIELD(ENUM8, keyboard_value_mask, led_mode);
          BITFIELD(KEYCODE, keyboard_value_mask, keyboard_key);
          BITFIELD(ENUM8, keyboard_value_mask, auto_repeat_mode);
          ENDBITMASK;
          break;

      case X_GetKeyboardControl:
          UNUSED(1);
          REQUEST_LENGTH();
          break;

      case X_Bell:
          INT8(percent);
          REQUEST_LENGTH();
          break;

      case X_ChangePointerControl:
          UNUSED(1);
          REQUEST_LENGTH();
          INT16(acceleration_numerator);
          INT16(acceleration_denominator);
          INT16(threshold);
          BOOL(do_acceleration);
          BOOL(do_threshold);
          break;

      case X_GetPointerControl:
          UNUSED(1);
          REQUEST_LENGTH();
          break;

      case X_SetScreenSaver:
          UNUSED(1);
          REQUEST_LENGTH();
          INT16(timeout);
          INT16(interval);
          ENUM8(prefer_blanking);
          ENUM8(allow_exposures);
          UNUSED(2);
          break;

      case X_GetScreenSaver:
          UNUSED(1);
          REQUEST_LENGTH();
          break;

      case X_ChangeHosts:
          ENUM8(change_host_mode);
          REQUEST_LENGTH();
          v8 = ENUM8(family);
          UNUSED(1);
          v16 = CARD16(address_length);
          if (v8 == FAMILY_INTERNET && v16 == 4) {
              /*
               * IPv4 addresses.
               * XXX - what about IPv6?  Is that a family of
               * FAMILY_INTERNET (0) with a length of 16?
               */
              LISTofIPADDRESS(ip_address, v16);
          } else
              LISTofCARD8(address, v16);
          break;

      case X_ListHosts:
          UNUSED(1);
          REQUEST_LENGTH();
          break;

      case X_SetAccessControl:
          ENUM8(access_mode);
          REQUEST_LENGTH();
          break;

      case X_SetCloseDownMode:
          ENUM8(close_down_mode);
          REQUEST_LENGTH();
          break;

      case X_KillClient:
          UNUSED(1);
          REQUEST_LENGTH();
          CARD32(resource);
          break;

      case X_RotateProperties:
          UNUSED(1);
          v16 = REQUEST_LENGTH();
          WINDOW(window);
          CARD16(property_number);
          INT16(delta);
          LISTofATOM(properties, (v16 - 12));
          break;

      case X_ForceScreenSaver:
          ENUM8(screen_saver_mode);
          REQUEST_LENGTH();
          break;

      case X_SetPointerMapping:
          v8 = FIELD8(map_length);
          REQUEST_LENGTH();
          LISTofCARD8(map, v8);
          PAD();
          break;

      case X_GetPointerMapping:
          UNUSED(1);
          REQUEST_LENGTH();
          break;

      case X_SetModifierMapping:
          v8 = FIELD8(keycodes_per_modifier);
          REQUEST_LENGTH();
          LISTofKEYCODE(state->modifiermap, keycodes, v8);
          break;

      case X_GetModifierMapping:
          UNUSED(1);
          REQUEST_LENGTH();
          break;

      case X_NoOperation:
          UNUSED(1);
          REQUEST_LENGTH();
          break;
      }

      if ((left = tvb_reported_length_remaining(tvb, offset)) > 0)
          UNDECODED(left);
}

static void dissect_x11_requests(tvbuff_t *tvb, packet_info *pinfo,
    proto_tree *tree)
{
      volatile int offset = 0;
      int length_remaining;
      volatile gboolean little_endian;
      guint8 opcode;
      volatile int plen;
      proto_item *ti;
      proto_tree *t;
      volatile gboolean is_initial_creq;
      guint16 auth_proto_len, auth_data_len;
      const char *volatile sep = NULL;
      conversation_t *conversation;
      x11_conv_data_t *state;
      int length;
      tvbuff_t *next_tvb;

      while (tvb_reported_length_remaining(tvb, offset) != 0) {
          /*
           * We use "tvb_ensure_length_remaining()" to make sure there
           * actually *is* data remaining.
           *
           * This means we're guaranteed that "length_remaining" is
           * positive.
           */
          length_remaining = tvb_ensure_length_remaining(tvb, offset);

          /*
           * Can we do reassembly?
           */
          if (x11_desegment && pinfo->can_desegment) {
              /*
               * Yes - is the X11 request header split across
               * segment boundaries?
               */
              if (length_remaining < 4) {
                  /*
                   * Yes.  Tell the TCP dissector where the data
                   * for this message starts in the data it handed
                   * us, and how many more bytes we need, and return.
                   */
                  pinfo->desegment_offset = offset;
                  pinfo->desegment_len = 4 - length_remaining;
                  return;
              }
          }

          /*
           * Get the state for this conversation; create the conversation
           * if we don't have one, and create the state if we don't have
           * any.
           */
          conversation = find_conversation(pinfo->fd->num, &pinfo->src, &pinfo->dst,
            pinfo->ptype, pinfo->srcport, pinfo->destport, 0);
          if (conversation == NULL) {
              /*
               * No - create one.
               */
              conversation = conversation_new(pinfo->fd->num, &pinfo->src,
                  &pinfo->dst, pinfo->ptype, pinfo->srcport,
                  pinfo->destport, 0);
          }

          /*
           * Is there state attached to this conversation?
           */
          if ((state = conversation_get_proto_data(conversation, proto_x11))
          == NULL)
            x11_stateinit(&state, conversation);

          /*
           * Guess the byte order if we don't already know it.
           */
          little_endian = guess_byte_ordering(tvb, pinfo, state);

          /*
           * Get the opcode and length of the putative X11 request.
           */
          opcode = VALUE8(tvb, 0);
          plen = VALUE16(tvb, offset + 2);

          if (plen == 0) {
              /*
               * This can't be 0, as it includes the header length.
               * A different choice of byte order wouldn't have
               * helped.
               * Give up.
               */
              ti = proto_tree_add_item(tree, proto_x11, tvb, offset, -1,
              FALSE);
              t = proto_item_add_subtree(ti, ett_x11);
              proto_tree_add_text(t, tvb, offset, -1,
              "Bogus request length (0)");
              return;
          }

          if (state->iconn_frame == pinfo->fd->num ||
            (g_hash_table_lookup(state->seqtable,
            GINT_TO_POINTER(state->sequencenumber)) == (int *)NOTHING_SEEN &&
               (opcode == 'B' || opcode == 'l') &&
               (plen == 11 || plen == 2816))) {
              /*
               * Either
               *
               *  we saw this on the first pass and this is
               *    it again
               *
               * or
               *    we haven't already seen any requests, the first
               *    byte of the message is 'B' or 'l', and the 16-bit
               *    integer 2 bytes into the data stream is either 11
               *    or a byte-swapped 11.
               *
               * This means it's probably an initial connection
               * request, not a message.
               *
               * 'B' is decimal 66, which is the opcode for a
               * PolySegment request; unfortunately, 11 is a valid
               * length for a PolySegment request request, so we
               * might mis-identify that request.  (Are there any
               * other checks we can do?)
               *
               * 'l' is decimal 108, which is the opcode for a
               * GetScreenSaver request; the only valid length
               * for that request is 1.
               */
              is_initial_creq = TRUE;

              /*
               * We now know the byte order.  Override the guess.
               */
              if (state->byte_order == BYTE_ORDER_UNKNOWN) {
                  if (opcode == 'B') {
                        /*
                         * Big-endian.
                         */
                        state->byte_order = BYTE_ORDER_BE;
                        little_endian = FALSE;
                  } else {
                        /*
                         * Little-endian.
                         */
                        state->byte_order = BYTE_ORDER_LE;
                        little_endian = TRUE;
                  }
              }

              /*
               * Can we do reassembly?
               */
              if (x11_desegment && pinfo->can_desegment) {
                  /*
                   * Yes - is the fixed-length portion of the
                   * initial connection header split across
                   * segment boundaries?
                   */
                  if (length_remaining < 10) {
                        /*
                         * Yes.  Tell the TCP dissector where the
                         * data for this message starts in the data
                         * it handed us, and how many more bytes we
                         * need, and return.
                         */
                        pinfo->desegment_offset = offset;
                        pinfo->desegment_len = 10 - length_remaining;
                        return;
                  }
              }

              /*
               * Get the lengths of the authorization protocol and
               * the authorization data.
               */
              auth_proto_len = VALUE16(tvb, offset + 6);
              auth_data_len = VALUE16(tvb, offset + 8);
              plen = 12 + ROUND_LENGTH(auth_proto_len) +
                  ROUND_LENGTH(auth_data_len);
          } else {
              /*
               * This is probably an ordinary request.
               */
              is_initial_creq = FALSE;

              /*
               * The length of a request is in 4-byte words.
               */
              plen *= 4;
          }

          /*
           * Can we do reassembly?
           */
          if (x11_desegment && pinfo->can_desegment) {
              /*
               * Yes - is the X11 request split across segment
               * boundaries?
               */
              if (length_remaining < plen) {
                  /*
                   * Yes.  Tell the TCP dissector where the data
                   * for this message starts in the data it handed
                   * us, and how many more bytes we need, and return.
                   */
                  pinfo->desegment_offset = offset;
                  pinfo->desegment_len = plen - length_remaining;
                  return;
              }
          }

          /*
           * Construct a tvbuff containing the amount of the payload
           * we have available.  Make its reported length the
           * amount of data in the X11 request.
           *
           * XXX - if reassembly isn't enabled. the subdissector
           * will throw a BoundsError exception, rather than a
           * ReportedBoundsError exception.  We really want a tvbuff
           * where the length is "length", the reported length is "plen",
           * and the "if the snapshot length were infinite" length is the
           * minimum of the reported length of the tvbuff handed to us
           * and "plen", with a new type of exception thrown if the offset
           * is within the reported length but beyond that third length,
           * with that exception getting the "Unreassembled Packet" error.
           */
          length = length_remaining;
          if (length > plen)
              length = plen;
          next_tvb = tvb_new_subset(tvb, offset, length, plen);

          /*
           * Set the column appropriately.
           */
          if (is_initial_creq) {
              if (check_col(pinfo->cinfo, COL_INFO))
                  col_set_str(pinfo->cinfo, COL_INFO,
                  "Initial connection request");
          } else {
              if (sep == NULL) {
                  /*
                   * We haven't set the column yet; set it.
                   */
                  if (check_col(pinfo->cinfo, COL_INFO))
                        col_add_str(pinfo->cinfo, COL_INFO, "Requests");

                  /*
                   * Initialize the separator.
                   */
                  sep = ":";
              }
          }

          /*
           * Dissect the X11 request.
           *
           * Catch the ReportedBoundsError exception; if this
           * particular message happens to get a ReportedBoundsError
           * exception, that doesn't mean that we should stop
           * dissecting X11 requests within this frame or chunk of
           * reassembled data.
           *
           * If it gets a BoundsError, we can stop, as there's nothing
           * more to see, so we just re-throw it.
           */
          TRY {
              if (is_initial_creq) {
                  dissect_x11_initial_conn(next_tvb, pinfo, tree,
                      state, little_endian);
              } else {
                  dissect_x11_request(next_tvb, pinfo, tree, sep,
                      state, little_endian);
              }
          }
          CATCH(BoundsError) {
              RETHROW;
          }
          CATCH(ReportedBoundsError) {
              show_reported_bounds_error(tvb, pinfo, tree);
          }
          ENDTRY;

          /*
           * Skip the X11 message.
           */
          offset += plen;

          sep = ",";
      }
}

static void
x11_stateinit(x11_conv_data_t **state, conversation_t *conversation)
{
      static x11_conv_data_t stateinit;
      int i = 0;

      *state = g_mem_chunk_alloc(x11_state_chunk);
      **state = stateinit; 

      /* initialise opcodes */
      while (1) {
        if (opcode_vals[i].strptr == NULL) break;
        (*state)->opcode_vals[i].value = opcode_vals[i].value;
        (*state)->opcode_vals[i].strptr = opcode_vals[i].strptr;
        i++;
      }
      while (i <= MAX_OPCODES) {
        (*state)->opcode_vals[i].value = 0;
        (*state)->opcode_vals[i].strptr = NULL;
        i++;
      }     

      (*state)->seqtable = g_hash_table_new(g_direct_hash, g_direct_equal);
      (*state)->valtable = g_hash_table_new(g_direct_hash, g_direct_equal);
            g_hash_table_insert((*state)->seqtable, (int *)0, (int *)NOTHING_SEEN);
      (*state)->byte_order = BYTE_ORDER_UNKNOWN; /* don't know yet*/
      conversation_add_proto_data(conversation, proto_x11, *state);
}


static void
dissect_x11_replies(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
/* Set up structures we will need to add the protocol subtree and manage it */
      volatile int offset, plen;
      tvbuff_t * volatile next_tvb;
      conversation_t *conversation;
      x11_conv_data_t *state;
      gboolean little_endian;
      int length_remaining;
      const char *volatile sep = NULL;


      /*
      * Get the state for this conversation; create the conversation
      * if we don't have one, and create the state if we don't have
      * any.
      */
      conversation = find_conversation(pinfo->fd->num, &pinfo->src, &pinfo->dst,
      pinfo->ptype, pinfo->srcport, pinfo->destport, 0);
      if (conversation == NULL) {
            /*
             * No - create one.
            */
            conversation = conversation_new(pinfo->fd->num, &pinfo->src, &pinfo->dst,
            pinfo->ptype, pinfo->srcport, pinfo->destport, 0);
      }

      /*
       * Is there state attached to this conversation?
      */
      if ((state = conversation_get_proto_data(conversation, proto_x11))
      == NULL) {
            /*
             * No - create a state structure and attach it.
             */
            x11_stateinit(&state, conversation);
      }

      /*
       * Guess the byte order if we don't already know it.
       */
      little_endian = guess_byte_ordering(tvb, pinfo, state);

      offset = 0;
      while (tvb_reported_length_remaining(tvb, offset) != 0) {
            /*
             * We use "tvb_ensure_length_remaining()" to make sure there
             * actually *is* data remaining.
             *
             * This means we're guaranteed that "length_remaining" is
             * positive.
             */
            length_remaining = tvb_ensure_length_remaining(tvb, offset);

            /*
            * Can we do reassembly?
            */
            if (x11_desegment && pinfo->can_desegment) {
                    /*
                     * Yes - is the X11 reply header split across
                     * segment boundaries?
                     */
                    if (length_remaining < 8) {
                        /*
                         * Yes.  Tell the TCP dissector where the data
                         * for this message starts in the data it handed
                         * us, and how many more bytes we need, and
                         * return.
                         */
                        pinfo->desegment_offset = offset;
                        pinfo->desegment_len = 4 - length_remaining;
                        return;
                  }
            }

            /*
             * Find out what kind of a reply it is.
             * There are four possible:
             *    - reply to initial connection
             *    - errorreply (a request generated an error)
             *    - requestreply (reply to a request)
             *    - event (some event occured)
             */
            if (g_hash_table_lookup(state->seqtable,
                GINT_TO_POINTER(state->sequencenumber)) == (int *)INITIAL_CONN 
                || (state->iconn_reply == pinfo->fd->num)) {
                  /*
                   * Either the connection is in the "initial
                   * connection" state, or this frame is known
                   * to have the initial connection reply.
                   * That means this is the initial connection
                   * reply.
                   */
                  plen = 8 + VALUE16(tvb, offset + 6) * 4;

                  HANDLE_REPLY(plen, length_remaining,
                      "Initial connection reply", 
                      dissect_x11_initial_reply); 
            } else {
                  /*
                   * This isn't an initial connection reply
                   * (XXX - unless we missed the initial
                   * connection request).  Look at the first
                   * byte to determine what it is; errors
                   * start with a byte of 0, replies start
                   * with a byte of 1, events start with
                   * a byte with of 2 or greater.
                   */
                  switch (tvb_get_guint8(tvb, offset)) {

                  case 0:
                        plen = 32;
                        HANDLE_REPLY(plen, length_remaining,
                            "Error", dissect_x11_error); 
                        break;

                  case 1:
                        /* replylength is in units of four. */
                        plen = 32 + VALUE32(tvb, offset + 4) * 4;

                        HANDLE_REPLY(plen, length_remaining,
                            "Reply", dissect_x11_reply); 
                        break;

                        default:
                              /* Event */
                        plen = 32;
                        HANDLE_REPLY(plen, length_remaining,
                            "Event", dissect_x11_event);
                        break;
                  }
            }

            offset += plen;
      }

      return;
}

static void
dissect_x11_reply(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
              const char *volatile sep, x11_conv_data_t *volatile state,
              gboolean little_endian)
{
      int offset = 0, *offsetp = &offset, length, left, opcode;
      int major_opcode, sequence_number;
      value_string *vals_p;
      proto_item *ti;
      proto_tree *t;
      
      ti = proto_tree_add_item(tree, proto_x11, tvb, 0,
                               tvb_reported_length_remaining(tvb, offset),
                               FALSE);
      t = proto_item_add_subtree(ti, ett_x11);


      /*
       * XXX - this doesn't work correctly if either
       *
       *    1) the request sequence number wraps in the lower 16
       *       bits;
       *
       *    2) we don't see the initial connection request and the
       *         resynchronization of sequence number fails and thus
       *       don't have the right sequence numbers 
       *
       *    3) we don't have all the packets in the capture and
       *       get out of sequence.
       *
       * We might, instead, want to assume that a reply is a reply to
       * the most recent not-already-replied-to request in the same
       * connection.  That also might mismatch replies to requests if
       * packets are lost, but there's nothing you can do to fix that.
       */

      sequence_number = VALUE16(tvb, offset + 2);
      opcode = GPOINTER_TO_INT(g_hash_table_lookup(state->seqtable,
                                GINT_TO_POINTER(sequence_number)));

      if (state->iconn_frame == 0 &&  state->resync == FALSE) {

            /*
             * We don't see the initial connection request and no
             * resynchronization has been performed yet (first reply),
             * set the current sequence number to the one of the 
             * current reply (this is only performed once).
             */
            state->sequencenumber = sequence_number;
            state->resync = TRUE;
      }

      if (opcode == UNKNOWN_OPCODE) {
            if (check_col(pinfo->cinfo, COL_INFO))
                  col_append_fstr(pinfo->cinfo, COL_INFO, 
                              "%s to unknown request", sep);
            proto_item_append_text(ti, ", Reply to unknown request");
      } else {
            if (check_col(pinfo->cinfo, COL_INFO))
                  col_append_fstr(pinfo->cinfo, COL_INFO, "%s %s",
                              sep,
                              val_to_str(opcode, state->opcode_vals, 
                                       "<Unknown opcode %d>"));

            proto_item_append_text(ti, ", Reply, opcode: %d (%s)", 
                               opcode, val_to_str(opcode, 
                                            state->opcode_vals,
                                            "<Unknown opcode %d>"));
      }

      switch (opcode) {

                  /*
                   * Replies that need special processing outside tree
             */

            case X_QueryExtension:    

                  /* 
                   * if extension is present and request is known:
                   * store opcode of extension in value_string of
                   * opcodes
                   */
                  if (!VALUE8(tvb, offset + 8)) {
                        /* not present */
                        break;
                  }

                  vals_p = g_hash_table_lookup(state->valtable,
                                         GINT_TO_POINTER(sequence_number));
                  if (vals_p != NULL) {
                        major_opcode = VALUE8(tvb, offset + 9);
                        vals_p->value = major_opcode;
                        g_hash_table_remove(state->valtable,
                                        GINT_TO_POINTER(sequence_number));
                  }
                  break;

            default:
                  break;
      }

      if (tree == NULL)
            return; 

      switch (opcode) {
                  /*
                   * Requests that expect a reply.
             */

            case X_GetWindowAttributes:
                  REPLYCONTENTS_COMMON();
                  break; 

            case X_GetGeometry:
                  REPLY(reply);
                  CARD8(depth);
                  SEQUENCENUMBER_REPLY(sequencenumber);
                  REPLYLENGTH(replylength);
                  WINDOW(rootwindow);
                  INT16(x);
                  INT16(y);
                  CARD16(width);
                  CARD16(height);
                  CARD16(border_width);
                  UNUSED(10);
                  break;

            case X_QueryTree:
                  REPLYCONTENTS_COMMON();
                  break; 

            case X_InternAtom:
                  REPLY(reply);
                  UNUSED(1);
                  SEQUENCENUMBER_REPLY(sequencenumber);
                  REPLYLENGTH(replylength);
                  ATOM(atom);
                  UNUSED(20);
                  break;

            case X_GetAtomName:
                  REPLYCONTENTS_COMMON();
                  break; 

            case X_GetProperty:
                  REPLY(reply);
                  CARD8(format);
                  SEQUENCENUMBER_REPLY(sequencenumber);
                  length = REPLYLENGTH(replylength);
                  ATOM(get_property_type);
                  CARD32(bytes_after);
                  CARD32(valuelength);
                  UNUSED(12);
                  break;

            case X_ListProperties:
                  REPLY(reply);
                  UNUSED(1);
                  SEQUENCENUMBER_REPLY(sequencenumber);
                  REPLYLENGTH(replylength);
                  length = CARD16(property_number);
                  UNUSED(22);
                  LISTofATOM(properties, length*4);
                  break;

            case X_GetSelectionOwner:
                  REPLY(reply);
                  UNUSED(1);
                  SEQUENCENUMBER_REPLY(sequencenumber);
                  REPLYLENGTH(replylength);
                  WINDOW(owner);
                  UNUSED(20);
                  break;

            case X_GrabPointer:
            case X_GrabKeyboard:
                  REPLY(reply);
                  ENUM8(grab_status);
                  SEQUENCENUMBER_REPLY(sequencenumber);
                  REPLYLENGTH(replylength);
                  UNUSED(24);
                  break;

            case X_QueryPointer:
                  REPLY(reply);
                  BOOL(same_screen);
                  SEQUENCENUMBER_REPLY(sequencenumber);
                  REPLYLENGTH(replylength);
                  WINDOW(rootwindow);
                  WINDOW(childwindow);
                  INT16(root_x);
                  INT16(root_y);
                  INT16(win_x);
                  INT16(win_y);
                  SETofKEYBUTMASK(mask);
                  UNUSED(6);
                  break; 

            case X_GetMotionEvents:
                  REPLYCONTENTS_COMMON();
                  break; 

            case X_TranslateCoords:
                  REPLY(reply);
                  BOOL(same_screen);
                  SEQUENCENUMBER_REPLY(sequencenumber);
                  REPLYLENGTH(replylength);
                  WINDOW(childwindow);
                  INT16(dst_x);
                  INT16(dst_y);
                  UNUSED(16);
                  break; 
                  
            case X_GetInputFocus:
                  REPLY(reply);
                  ENUM8(revert_to);
                  SEQUENCENUMBER_REPLY(sequencenumber);
                  REPLYLENGTH(replylength);
                  WINDOW(focus);
                  UNUSED(20);
                  break;

            case X_QueryKeymap:
                  REPLY(reply);
                  UNUSED(1);
                  SEQUENCENUMBER_REPLY(sequencenumber);
                  REPLYLENGTH(replylength);
                  LISTofCARD8(keys, 32);
                  break;

            case X_QueryFont:
            case X_QueryTextExtents:
            case X_ListFonts:
            case X_GetImage:
            case X_ListInstalledColormaps:
                  REPLYCONTENTS_COMMON();
                  break;

            case X_AllocColor:
                  REPLY(reply);
                  UNUSED(1);
                  SEQUENCENUMBER_REPLY(sequencenumber);
                  REPLYLENGTH(replylength);
                  CARD16(red);
                  CARD16(green);
                  CARD16(blue);
                  UNUSED(2);
                  CARD32(pixel);
                  UNUSED(12);
                  break;

            case X_QueryColors:
                  REPLYCONTENTS_COMMON();
                  break;

            case X_LookupColor:
                  REPLY(reply);
                  UNUSED(1);
                  SEQUENCENUMBER_REPLY(sequencenumber);
                  REPLYLENGTH(replylength);
                  CARD16(exact_red);
                  CARD16(exact_green);
                  CARD16(exact_blue);
                  CARD16(visual_red);
                  CARD16(visual_green);
                  CARD16(visual_blue);
                  UNUSED(12);
                  break;

            case X_QueryBestSize:
                  REPLY(reply);
                  UNUSED(1);
                  SEQUENCENUMBER_REPLY(sequencenumber);
                  REPLYLENGTH(replylength);
                  CARD16(width);
                  CARD16(height);
                  UNUSED(20);
                  break;

            case X_QueryExtension:
                  REPLY(reply);
                  UNUSED(1);
                  SEQUENCENUMBER_REPLY(sequencenumber);
                  REPLYLENGTH(replylength);
                  BOOL(present);
                  CARD8(major_opcode);
                  CARD8(first_event);
                  CARD8(first_error);
                  UNUSED(20);
                  break;
              
            case X_ListExtensions:
                  REPLYCONTENTS_COMMON();
                  break; 

            case X_GetKeyboardMapping:
                  state->first_keycode =
                        state->request.GetKeyboardMapping.first_keycode;
                  REPLY(reply);
                  state->keysyms_per_keycode =
                        FIELD8(keysyms_per_keycode);
                  SEQUENCENUMBER_REPLY(sequencenumber);
                  length = REPLYLENGTH(replylength);
                  UNUSED(24);
                  LISTofKEYSYM(keysyms, state->keycodemap,
                             state->request.GetKeyboardMapping.first_keycode, 
                             length / state->keysyms_per_keycode,
                             state->keysyms_per_keycode);
                  break; 

            case X_GetKeyboardControl:
                  REPLYCONTENTS_COMMON();
                  break; 

            case X_GetPointerControl:
                  REPLY(reply);
                  UNUSED(1);
                  SEQUENCENUMBER_REPLY(sequencenumber);
                  REPLYLENGTH(replylength);
                  CARD16(acceleration_numerator);
                  CARD16(acceleration_denominator);
                  CARD16(threshold);
                  UNUSED(18);
                  break;

            case X_GetScreenSaver:
                  REPLY(reply);
                  UNUSED(1);
                  SEQUENCENUMBER_REPLY(sequencenumber);
                  REPLYLENGTH(replylength);
                  CARD16(timeout);
                  CARD16(interval);
                  ENUM8(prefer_blanking);
                  ENUM8(allow_exposures);
                  UNUSED(18);
                  break;

            case X_ListHosts:
            case X_SetPointerMapping:
            case X_GetPointerMapping:
            case X_SetModifierMapping:
                  REPLYCONTENTS_COMMON();
                  break; 

            case X_GetModifierMapping:
                  REPLY(reply);
                  state->keycodes_per_modifier =
                        FIELD8(keycodes_per_modifier);
                  SEQUENCENUMBER_REPLY(sequencenumber);
                  REPLYLENGTH(replylength);
                  UNUSED(24);
                  LISTofKEYCODE(state->modifiermap, keycodes,
                              state->keycodes_per_modifier);
                  break; 

            default:
                  REPLYCONTENTS_COMMON();
      }

            if ((left = tvb_reported_length_remaining(tvb, offset)) > 0)
          UNDECODED(left);
}

static void
same_screen_focus(tvbuff_t *tvb, int *offsetp, proto_tree *t)
{
      proto_item *ti;
      guint32 bitmask_value;
      int bitmask_offset;
      int bitmask_size;
      proto_tree *bitmask_tree;

      bitmask_value = VALUE8(tvb, *offsetp);
      bitmask_offset = *offsetp;
      bitmask_size = 1;

      ti = proto_tree_add_uint(t, hf_x11_same_screen_focus_mask, tvb, *offsetp, 1,
                                     bitmask_value);
      bitmask_tree = proto_item_add_subtree(ti, ett_x11_same_screen_focus);
      FLAG(same_screen_focus, focus);
      FLAG(same_screen_focus, same_screen);

      *offsetp += 1;
}

static void
dissect_x11_event(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
              const char *volatile sep, x11_conv_data_t *volatile state,
              gboolean little_endian)
{
      int offset = 0, *offsetp = &offset, left;
      unsigned char eventcode;
      proto_item *ti;
      proto_tree *t;

      ti = proto_tree_add_item(tree, proto_x11, tvb, 0, -1, FALSE);
      t = proto_item_add_subtree(ti, ett_x11);

      eventcode = tvb_get_guint8(tvb, offset);

      if (check_col(pinfo->cinfo, COL_INFO))
            col_append_fstr(pinfo->cinfo, COL_INFO, "%s %s",
                        sep, val_to_str(eventcode, eventcode_vals,
                        "<Unknown eventcode %u>"));

      proto_tree_add_uint_format(t, hf_x11_eventcode, tvb, offset, 1,
                           eventcode, 
                           "eventcode: %d (%s)",
                           eventcode, 
                           val_to_str(eventcode, eventcode_vals,
                           "<Unknown eventcode %u>"));
      ++offset;

      proto_item_append_text(ti, ", Event, eventcode: %d (%s)", 
                        eventcode, val_to_str(eventcode, eventcode_vals,
                        "<Unknown eventcode %u>"));

      if (tree == NULL)
            return; 

      switch (eventcode) {
            case KeyPress:
            case KeyRelease: {
                  int code, mask;

                  /* need to do some prefetching here ... */
                  code = VALUE8(tvb, offset);
                  mask = VALUE16(tvb, 28);

                  KEYCODE_DECODED(keycode, code, mask);
                  CARD16(event_sequencenumber);
                  EVENTCONTENTS_COMMON();
                  BOOL(same_screen);
                  UNUSED(1);
                  break;
            }

            case ButtonPress:
            case ButtonRelease:
                  BUTTON(eventbutton);
                  CARD16(event_sequencenumber);
                  EVENTCONTENTS_COMMON();
                  BOOL(same_screen);
                  UNUSED(1);
                  break;

            case MotionNotify:
                  CARD8(detail);
                  CARD16(event_sequencenumber);
                  EVENTCONTENTS_COMMON();
                  BOOL(same_screen);
                  UNUSED(1);
                  break;

            case EnterNotify:
            case LeaveNotify:
                  ENUM8(event_detail);
                  CARD16(event_sequencenumber);
                  EVENTCONTENTS_COMMON();
                  ENUM8(grab_mode);
                  same_screen_focus(tvb, offsetp, t);
                  break;

            case FocusIn:
            case FocusOut:
                  ENUM8(focus_detail);
                  CARD16(event_sequencenumber);
                  WINDOW(eventwindow);
                  ENUM8(focus_mode);
                  UNUSED(23);
                  break;

            case KeymapNotify:
                  break;

            case Expose:
                  UNUSED(1);
                  CARD16(event_sequencenumber);
                  WINDOW(eventwindow);
                  INT16(x);
                  INT16(y);
                  CARD16(width);
                  CARD16(height);
                  CARD16(count);
                  UNUSED(14);
                  break;

            case GraphicsExpose:
                  UNUSED(1);
                  CARD16(event_sequencenumber);
                  DRAWABLE(drawable);
                  CARD16(x);
                  CARD16(y);
                  CARD16(width);
                  CARD16(height);
                  CARD16(minor_opcode);
                  CARD16(count);
                  CARD8(major_opcode);
                  UNUSED(11);
                  break;

            case NoExpose:
                  UNUSED(1);
                  CARD16(event_sequencenumber);
                  DRAWABLE(drawable);
                  CARD16(minor_opcode);
                  CARD8(major_opcode);
                  UNUSED(21);
                  break;

            case VisibilityNotify:
                  UNUSED(1);
                  CARD16(event_sequencenumber);
                  WINDOW(eventwindow);
                  ENUM8(visibility_state);
                  UNUSED(23);
                  break;

            case CreateNotify:
                  UNUSED(1);
                  CARD16(event_sequencenumber);
                  WINDOW(parent);
                  WINDOW(eventwindow);
                  INT16(x);
                  INT16(y);
                  CARD16(width);
                  CARD16(height);
                  CARD16(border_width);
                  BOOL(override_redirect);
                  UNUSED(9);
                  break;

            case DestroyNotify:
                  UNUSED(1);
                  CARD16(event_sequencenumber);
                  WINDOW(eventwindow);
                  WINDOW(window);
                  UNUSED(20);
                  break;

            case UnmapNotify:
                  UNUSED(1);
                  CARD16(event_sequencenumber);
                  WINDOW(eventwindow);
                  WINDOW(window);
                  BOOL(from_configure);
                  UNUSED(19);
                  break;

            case MapNotify:
                  UNUSED(1);
                  CARD16(event_sequencenumber);
                  WINDOW(eventwindow);
                  WINDOW(window);
                  BOOL(override_redirect);
                  UNUSED(19);
                  break;

            case MapRequest:
                  UNUSED(1);
                  CARD16(event_sequencenumber);
                  WINDOW(parent);
                  WINDOW(eventwindow);
                  UNUSED(20);
                  break;

            case ReparentNotify:
                  UNUSED(1);
                  CARD16(event_sequencenumber);
                  WINDOW(eventwindow);
                  WINDOW(window);
                  WINDOW(parent);
                  INT16(x);
                  INT16(y);
                  BOOL(override_redirect);
                  UNUSED(11);
                  break;

            case ConfigureNotify:
                  UNUSED(1);
                  CARD16(event_sequencenumber);
                  WINDOW(eventwindow);
                  WINDOW(window);
                  WINDOW(above_sibling);
                  INT16(x);
                  INT16(y);
                  CARD16(width);
                  CARD16(height);
                  CARD16(border_width);
                  BOOL(override_redirect);
                  UNUSED(5);
                  break;

            case ConfigureRequest:
                  break;

            case GravityNotify:
                  UNUSED(1);
                  CARD16(event_sequencenumber);
                  WINDOW(eventwindow);
                  WINDOW(window);
                  INT16(x);
                  INT16(y);
                  UNUSED(16);
                  break;

            case ResizeRequest:
                  UNUSED(1);
                  CARD16(event_sequencenumber);
                  WINDOW(eventwindow);
                  CARD16(width);
                  CARD16(height);
                  UNUSED(20);
                  break;

            case CirculateNotify:
                  UNUSED(1);
                  CARD16(event_sequencenumber);
                  WINDOW(eventwindow);
                  WINDOW(window);
                  UNUSED(4);
                  ENUM8(place);
                  UNUSED(15);
                  break;

            case CirculateRequest:
                  UNUSED(1);
                  CARD16(event_sequencenumber);
                  WINDOW(parent);
                  WINDOW(eventwindow);
                  UNUSED(4);
                  ENUM8(place);
                  UNUSED(15);
                  break;

            case PropertyNotify:
                  UNUSED(1);
                  CARD16(event_sequencenumber);
                  WINDOW(eventwindow);
                  ATOM(atom);
                  TIMESTAMP(time);
                  ENUM8(property_state);
                  UNUSED(15);
                  break;

            case SelectionClear:
                  UNUSED(1);
                  CARD16(event_sequencenumber);
                  TIMESTAMP(time);
                  WINDOW(owner);
                  ATOM(selection);
                  UNUSED(16);
                  break;

            case SelectionRequest:
                  UNUSED(1);
                  CARD16(event_sequencenumber);
                  TIMESTAMP(time);
                  WINDOW(owner);
                  WINDOW(requestor);
                  ATOM(selection);
                  ATOM(target);
                  ATOM(property);
                  UNUSED(4);
                  break;

            case SelectionNotify:
                  UNUSED(1);
                  CARD16(event_sequencenumber);
                  TIMESTAMP(time);
                  WINDOW(requestor);
                  ATOM(selection);
                  ATOM(target);
                  ATOM(property);
                  UNUSED(8);
                  break;

            case ColormapNotify:
                  UNUSED(1);
                  CARD16(event_sequencenumber);
                  WINDOW(eventwindow);
                  COLORMAP(cmap);
                  BOOL(new);
                  ENUM8(colormap_state);
                  UNUSED(18);
                  break;

            case ClientMessage:
                  CARD8(format);
                  CARD16(event_sequencenumber);
                  WINDOW(eventwindow);
                  ATOM(type);
                  LISTofBYTE(data, 20);
                  break;

            case MappingNotify:
            default:
                  break;
      }

            if ((left = tvb_reported_length_remaining(tvb, offset)) > 0) 
          UNDECODED(left);

      return;
}

static void
dissect_x11_error(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
              const char *volatile sep, x11_conv_data_t *volatile state _U_,
              gboolean little_endian)
{
      int offset = 0, *offsetp = &offset, left;
      unsigned char errorcode, error;
      proto_item *ti;
      proto_tree *t;

      ti = proto_tree_add_item(tree, proto_x11, tvb, 0, -1, FALSE);
      t = proto_item_add_subtree(ti, ett_x11);

      error = tvb_get_guint8(tvb, offset);
      CARD8(error);

      errorcode = tvb_get_guint8(tvb, offset);
      if (check_col(pinfo->cinfo, COL_INFO))
            col_append_fstr(pinfo->cinfo, COL_INFO, "%s %s",
            sep, val_to_str(errorcode, errorcode_vals, "<Unknown errorcode %u>"));

      proto_tree_add_uint_format(t, hf_x11_errorcode, tvb, offset, 1,
                           errorcode, 
                           "errorcode: %d (%s)",
                           errorcode, 
                           val_to_str(errorcode, errorcode_vals,
                           "<Unknown errocode %u>"));
      ++offset;

        proto_item_append_text(ti, ", Error, errorcode: %d (%s)", 
                              errorcode, val_to_str(errorcode, errorcode_vals,
                              "<Unknown errorcode %u>"));

      if (tree == NULL)
            return; 

      CARD16(error_sequencenumber);

      switch (errorcode) {
            case BadValue:
                  CARD32(error_badvalue);
                  break;

            default:
                  UNDECODED(4);
      }

      CARD16(minor_opcode);
      CARD8(major_opcode);

            if ((left = tvb_reported_length_remaining(tvb, offset)) > 0)
          UNDECODED(left);
}

                  

/************************************************************************
 ***                                                                  ***
 ***         I N I T I A L I Z A T I O N   A N D   M A I N            ***
 ***                                                                  ***
 ************************************************************************/

static void
dissect_x11(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
      if (check_col(pinfo->cinfo, COL_PROTOCOL))
            col_set_str(pinfo->cinfo, COL_PROTOCOL, "X11");

      if (pinfo->match_port == pinfo->srcport)
            dissect_x11_replies(tvb, pinfo, tree);
      else
            dissect_x11_requests(tvb, pinfo, tree);
}

/* Register the protocol with Ethereal */
void proto_register_x11(void)
{

/* Setup list of header fields */
      static hf_register_info hf[] = {
#include "x11-register-info.h"
      };

/* Setup protocol subtree array */
      static gint *ett[] = {
          &ett_x11,
          &ett_x11_color_flags,
          &ett_x11_list_of_arc,
          &ett_x11_arc,
          &ett_x11_list_of_atom,
          &ett_x11_list_of_card32,
          &ett_x11_list_of_color_item,
          &ett_x11_color_item,
          &ett_x11_list_of_keycode,
          &ett_x11_list_of_keysyms,
          &ett_x11_keysym,
          &ett_x11_list_of_point,
          &ett_x11_point,
          &ett_x11_list_of_rectangle,
          &ett_x11_rectangle,
          &ett_x11_list_of_segment,
          &ett_x11_segment,
          &ett_x11_list_of_string8,
          &ett_x11_list_of_text_item,
          &ett_x11_text_item,
          &ett_x11_gc_value_mask,
          &ett_x11_event_mask,
          &ett_x11_do_not_propagate_mask,
          &ett_x11_set_of_key_mask,
          &ett_x11_pointer_event_mask,
          &ett_x11_window_value_mask,
          &ett_x11_configure_window_mask,
          &ett_x11_keyboard_value_mask,
          &ett_x11_same_screen_focus,
      };
      module_t *x11_module;

/* Register the protocol name and description */
      proto_x11 = proto_register_protocol("X11", "X11", "x11");

/* Required function calls to register the header fields and subtrees used */
      proto_register_field_array(proto_x11, hf, array_length(hf));
      proto_register_subtree_array(ett, array_length(ett));

      register_init_routine(x11_init_protocol);

      x11_module = prefs_register_protocol(proto_x11, NULL);
      prefs_register_bool_preference(x11_module, "desegment",
          "Reassemble X11 messages spanning multiple TCP segments",
          "Whether the X11 dissector should reassemble messages spanning multiple TCP segments. "
          "To use this option, you must also enable \"Allow subdissectors to reassemble TCP streams\" in the TCP protocol settings.",
          &x11_desegment);
}

void
proto_reg_handoff_x11(void)
{
  dissector_handle_t x11_handle;

  x11_handle = create_dissector_handle(dissect_x11, proto_x11);
  dissector_add("tcp.port", TCP_PORT_X11, x11_handle);
  dissector_add("tcp.port", TCP_PORT_X11_2, x11_handle);
  dissector_add("tcp.port", TCP_PORT_X11_3, x11_handle);
  data_handle = find_dissector("data");
}


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