First import

[xorg_rtime.git] / xorg-server-1.4 / dix / dixutils.c

/***********************************************************

Copyright 1987, 1998  The Open Group

Permission to use, copy, modify, distribute, and sell this software and its
documentation for any purpose is hereby granted without fee, provided that
the above copyright notice appear in all copies and that both that
copyright notice and this permission notice appear in supporting
documentation.

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
OPEN GROUP BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Except as contained in this notice, the name of The Open Group shall not be
used in advertising or otherwise to promote the sale, use or other dealings
in this Software without prior written authorization from The Open Group.


Copyright 1987 by Digital Equipment Corporation, Maynard, Massachusetts.

                        All Rights Reserved

Permission to use, copy, modify, and distribute this software and its 
documentation for any purpose and without fee is hereby granted, 
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in 
supporting documentation, and that the name of Digital not be
used in advertising or publicity pertaining to distribution of the
software without specific, written prior permission.  

DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
SOFTWARE.

******************************************************************/

/*

(c)Copyright 1988,1991 Adobe Systems Incorporated. All rights reserved.

Permission to use, copy, modify, distribute, and sublicense this software and its
documentation for any purpose and without fee is hereby granted, provided that
the above copyright notices appear in all copies and that both those copyright
notices and this permission notice appear in supporting documentation and that
the name of Adobe Systems Incorporated not be used in advertising or publicity
pertaining to distribution of the software without specific, written prior
permission.  No trademark license to use the Adobe trademarks is hereby
granted.  If the Adobe trademark "Display PostScript"(tm) is used to describe
this software, its functionality or for any other purpose, such use shall be
limited to a statement that this software works in conjunction with the Display
PostScript system.  Proper trademark attribution to reflect Adobe's ownership
of the trademark shall be given whenever any such reference to the Display
PostScript system is made.

ADOBE MAKES NO REPRESENTATIONS ABOUT THE SUITABILITY OF THE SOFTWARE FOR ANY
PURPOSE.  IT IS PROVIDED "AS IS" WITHOUT EXPRESS OR IMPLIED WARRANTY.  ADOBE
DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-
INFRINGEMENT OF THIRD PARTY RIGHTS.  IN NO EVENT SHALL ADOBE BE LIABLE TO YOU
OR ANY OTHER PARTY FOR ANY SPECIAL, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY
DAMAGES WHATSOEVER WHETHER IN AN ACTION OF CONTRACT,NEGLIGENCE, STRICT
LIABILITY OR ANY OTHER ACTION ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.  ADOBE WILL NOT PROVIDE ANY TRAINING OR OTHER
SUPPORT FOR THE SOFTWARE.

Adobe, PostScript, and Display PostScript are trademarks of Adobe Systems
Incorporated which may be registered in certain jurisdictions.

Author:  Adobe Systems Incorporated

*/


#ifdef HAVE_DIX_CONFIG_H
#include <dix-config.h>
#endif

#include <X11/X.h>
#include <X11/Xmd.h>
#include "misc.h"
#include "windowstr.h"
#include "dixstruct.h"
#include "pixmapstr.h"
#include "scrnintstr.h"
#define  XK_LATIN1
#include <X11/keysymdef.h>
#include "xace.h"

/*
 * CompareTimeStamps returns -1, 0, or +1 depending on if the first
 * argument is less than, equal to or greater than the second argument.
 */

_X_EXPORT int
CompareTimeStamps(TimeStamp a, TimeStamp b)
{
    if (a.months < b.months)
        return EARLIER;
    if (a.months > b.months)
        return LATER;
    if (a.milliseconds < b.milliseconds)
        return EARLIER;
    if (a.milliseconds > b.milliseconds)
        return LATER;
    return SAMETIME;
}

/*
 * convert client times to server TimeStamps
 */

#define HALFMONTH ((unsigned long) 1<<31)
_X_EXPORT TimeStamp
ClientTimeToServerTime(CARD32 c)
{
    TimeStamp ts;
    if (c == CurrentTime)
        return currentTime;
    ts.months = currentTime.months;
    ts.milliseconds = c;
    if (c > currentTime.milliseconds)
    {
        if (((unsigned long) c - currentTime.milliseconds) > HALFMONTH)
            ts.months -= 1;
    }
    else if (c < currentTime.milliseconds)
    {
        if (((unsigned long)currentTime.milliseconds - c) > HALFMONTH)
            ts.months += 1;
    }
    return ts;
}

/*
 * ISO Latin-1 case conversion routine
 *
 * this routine always null-terminates the result, so
 * beware of too-small buffers
 */

static unsigned char
ISOLatin1ToLower (unsigned char source)
{
    unsigned char   dest;
    if ((source >= XK_A) && (source <= XK_Z))
       dest = source + (XK_a - XK_A);
    else if ((source >= XK_Agrave) && (source <= XK_Odiaeresis))
       dest = source + (XK_agrave - XK_Agrave);
    else if ((source >= XK_Ooblique) && (source <= XK_Thorn))
       dest = source + (XK_oslash - XK_Ooblique);
    else
       dest = source;
    return dest;
}


_X_EXPORT void
CopyISOLatin1Lowered(unsigned char *dest, unsigned char *source, int length)
{
    int i;

    for (i = 0; i < length; i++, source++, dest++)
        *dest = ISOLatin1ToLower (*source);
    *dest = '\0';
}

int
CompareISOLatin1Lowered(unsigned char *s1, int s1len, 
                        unsigned char *s2, int s2len)
{
    unsigned char   c1, c2;
    
    for (;;) 
    {
        /* note -- compare against zero so that -1 ignores len */
        c1 = s1len-- ? *s1++ : '\0';
        c2 = s2len-- ? *s2++ : '\0';
        if (!c1 || 
            (c1 != c2 && 
             (c1 = ISOLatin1ToLower (c1)) != (c2 = ISOLatin1ToLower (c2))))
            break;
    }
    return (int) c1 - (int) c2;
}

/*
 * dixLookupWindow and dixLookupDrawable:
 * Look up the window/drawable taking into account the client doing the
 * lookup, the type of drawable desired, and the type of access desired.
 * Return Success with *pDraw set if the window/drawable exists and the client
 * is allowed access, else return an error code with *pDraw set to NULL.  The
 * access mask values are defined in resource.h.  The type mask values are
 * defined in pixmap.h, with zero equivalent to M_DRAWABLE.
 */
_X_EXPORT int
dixLookupDrawable(DrawablePtr *pDraw, XID id, ClientPtr client,
                  Mask type, Mask access)
{
    DrawablePtr pTmp;
    RESTYPE rtype;
    *pDraw = NULL;
    client->errorValue = id;

    if (id == INVALID)
        return BadDrawable;

    if (id == client->lastDrawableID) {
        pTmp = client->lastDrawable;

        /* an access check is required for cached drawables */
        rtype = (type & M_WINDOW) ? RT_WINDOW : RT_PIXMAP;
        if (!XaceHook(XACE_RESOURCE_ACCESS, client, id, rtype, access, pTmp))
            return BadDrawable;
    } else
        pTmp = (DrawablePtr)SecurityLookupIDByClass(client, id, RC_DRAWABLE,
                                                   access);
    if (!pTmp)
        return BadDrawable;
    if (!((1 << pTmp->type) & (type ? type : M_DRAWABLE)))
        return BadMatch;

    if (type & M_DRAWABLE) {
        client->lastDrawable = pTmp;
        client->lastDrawableID = id;
        client->lastGCID = INVALID;
        client->lastGC = (GCPtr)NULL;
    }
    *pDraw = pTmp;
    return Success;
}

_X_EXPORT int
dixLookupWindow(WindowPtr *pWin, XID id, ClientPtr client, Mask access)
{
    int rc;
    rc = dixLookupDrawable((DrawablePtr*)pWin, id, client, M_WINDOW, access);
    return (rc == BadDrawable) ? BadWindow : rc;
}

_X_EXPORT int
dixLookupGC(GCPtr *pGC, XID id, ClientPtr client, Mask access)
{
    GCPtr pTmp = (GCPtr)SecurityLookupIDByType(client, id, RT_GC, access);
    if (pTmp) {
        *pGC = pTmp;
        return Success;
    }
    client->errorValue = id;
    *pGC = NULL;
    return BadGC;
}

_X_EXPORT int
dixLookupClient(ClientPtr *pClient, XID rid, ClientPtr client, Mask access)
{
    pointer pRes = (pointer)SecurityLookupIDByClass(client, rid, RC_ANY,
                                                    access);
    int clientIndex = CLIENT_ID(rid);
    client->errorValue = rid;

    if (clientIndex && pRes && clients[clientIndex] && !(rid & SERVER_BIT)) {
        *pClient = clients[clientIndex];
        return Success;
    }
    *pClient = NULL;
    return BadValue;
}

/*
 * These are deprecated compatibility functions and will be removed soon!
 * Please use the new dixLookup*() functions above.
 */
_X_EXPORT _X_DEPRECATED WindowPtr
SecurityLookupWindow(XID id, ClientPtr client, Mask access_mode)
{
    WindowPtr pWin;
    int i = dixLookupWindow(&pWin, id, client, access_mode);
    static int warn = 1;
    if (warn-- > 0)
        ErrorF("Warning: LookupWindow()/SecurityLookupWindow() "
               "are deprecated.  Please convert your driver/module "
               "to use dixLookupWindow().\n");
    return (i == Success) ? pWin : NULL;
}

_X_EXPORT _X_DEPRECATED WindowPtr
LookupWindow(XID id, ClientPtr client)
{
    return SecurityLookupWindow(id, client, DixUnknownAccess);
}

_X_EXPORT _X_DEPRECATED pointer
SecurityLookupDrawable(XID id, ClientPtr client, Mask access_mode)
{
    DrawablePtr pDraw;
    int i = dixLookupDrawable(&pDraw, id, client, M_DRAWABLE, access_mode);
    static int warn = 1;
    if (warn-- > 0)
        ErrorF("Warning: LookupDrawable()/SecurityLookupDrawable() "
               "are deprecated.  Please convert your driver/module "
               "to use dixLookupDrawable().\n");
    return (i == Success) ? pDraw : NULL;
}

_X_EXPORT _X_DEPRECATED pointer
LookupDrawable(XID id, ClientPtr client)
{
    return SecurityLookupDrawable(id, client, DixUnknownAccess);
}

_X_EXPORT _X_DEPRECATED ClientPtr
LookupClient(XID id, ClientPtr client)
{
    ClientPtr pClient;
    int i = dixLookupClient(&pClient, id, client, DixUnknownAccess);
    static int warn = 1;
    if (warn-- > 0)
        ErrorF("Warning: LookupClient() is deprecated.  Please convert your "
               "driver/module to use dixLookupClient().\n");
    return (i == Success) ? pClient : NULL;
}

/* end deprecated functions */

int
AlterSaveSetForClient(ClientPtr client, WindowPtr pWin, unsigned mode,
                      Bool toRoot, Bool remap)
{
    int numnow;
    SaveSetElt *pTmp = NULL;
    int j;

    numnow = client->numSaved;
    j = 0;
    if (numnow)
    {
        pTmp = client->saveSet;
        while ((j < numnow) && (SaveSetWindow(pTmp[j]) != (pointer)pWin))
            j++;
    }
    if (mode == SetModeInsert)
    {
        if (j < numnow)         /* duplicate */
           return(Success);
        numnow++;
        pTmp = (SaveSetElt *)xrealloc(client->saveSet, sizeof(*pTmp) * numnow);
        if (!pTmp)
            return(BadAlloc);
        client->saveSet = pTmp;
        client->numSaved = numnow;
        SaveSetAssignWindow(client->saveSet[numnow - 1], pWin);
        SaveSetAssignToRoot(client->saveSet[numnow - 1], toRoot);
        SaveSetAssignRemap(client->saveSet[numnow - 1], remap);
        return(Success);
    }
    else if ((mode == SetModeDelete) && (j < numnow))
    {
        while (j < numnow-1)
        {
           pTmp[j] = pTmp[j+1];
           j++;
        }
        numnow--;
        if (numnow)
        {
            pTmp = (SaveSetElt *)xrealloc(client->saveSet, sizeof(*pTmp) * numnow);
            if (pTmp)
                client->saveSet = pTmp;
        }
        else
        {
            xfree(client->saveSet);
            client->saveSet = (SaveSetElt *)NULL;
        }
        client->numSaved = numnow;
        return(Success);
    }
    return(Success);
}

void
DeleteWindowFromAnySaveSet(WindowPtr pWin)
{
    int i;
    ClientPtr client;
    
    for (i = 0; i< currentMaxClients; i++)
    {    
        client = clients[i];
        if (client && client->numSaved)
            (void)AlterSaveSetForClient(client, pWin, SetModeDelete, FALSE, TRUE);
    }
}

/* No-op Don't Do Anything : sometimes we need to be able to call a procedure
 * that doesn't do anything.  For example, on screen with only static
 * colormaps, if someone calls install colormap, it's easier to have a dummy
 * procedure to call than to check if there's a procedure 
 */
_X_EXPORT void
NoopDDA(void)
{
}

typedef struct _BlockHandler {
    BlockHandlerProcPtr BlockHandler;
    WakeupHandlerProcPtr WakeupHandler;
    pointer blockData;
    Bool    deleted;
} BlockHandlerRec, *BlockHandlerPtr;

static BlockHandlerPtr  handlers;
static int              numHandlers;
static int              sizeHandlers;
static Bool             inHandler;
static Bool             handlerDeleted;

/**
 * 
 *  \param pTimeout   DIX doesn't want to know how OS represents time
 *  \param pReadMask  nor how it represents the det of descriptors
 */
void
BlockHandler(pointer pTimeout, pointer pReadmask)
{
    int i, j;
    
    ++inHandler;
    for (i = 0; i < screenInfo.numScreens; i++)
        (* screenInfo.screens[i]->BlockHandler)(i, 
                                screenInfo.screens[i]->blockData,
                                pTimeout, pReadmask);
    for (i = 0; i < numHandlers; i++)
        (*handlers[i].BlockHandler) (handlers[i].blockData,
                                     pTimeout, pReadmask);
    if (handlerDeleted)
    {
        for (i = 0; i < numHandlers;)
            if (handlers[i].deleted)
            {
                for (j = i; j < numHandlers - 1; j++)
                    handlers[j] = handlers[j+1];
                numHandlers--;
            }
            else
                i++;
        handlerDeleted = FALSE;
    }
    --inHandler;
}

/**
 *
 *  \param result    32 bits of undefined result from the wait
 *  \param pReadmask the resulting descriptor mask
 */
void
WakeupHandler(int result, pointer pReadmask)
{
    int i, j;

    ++inHandler;
    for (i = numHandlers - 1; i >= 0; i--)
        (*handlers[i].WakeupHandler) (handlers[i].blockData,
                                      result, pReadmask);
    for (i = 0; i < screenInfo.numScreens; i++)
        (* screenInfo.screens[i]->WakeupHandler)(i, 
                                screenInfo.screens[i]->wakeupData,
                                result, pReadmask);
    if (handlerDeleted)
    {
        for (i = 0; i < numHandlers;)
            if (handlers[i].deleted)
            {
                for (j = i; j < numHandlers - 1; j++)
                    handlers[j] = handlers[j+1];
                numHandlers--;
            }
            else
                i++;
        handlerDeleted = FALSE;
    }
    --inHandler;
}

/**
 * Reentrant with BlockHandler and WakeupHandler, except wakeup won't
 * get called until next time
 */
_X_EXPORT Bool
RegisterBlockAndWakeupHandlers (BlockHandlerProcPtr blockHandler, 
                                WakeupHandlerProcPtr wakeupHandler, 
                                pointer blockData)
{
    BlockHandlerPtr new;

    if (numHandlers >= sizeHandlers)
    {
        new = (BlockHandlerPtr) xrealloc (handlers, (numHandlers + 1) *
                                          sizeof (BlockHandlerRec));
        if (!new)
            return FALSE;
        handlers = new;
        sizeHandlers = numHandlers + 1;
    }
    handlers[numHandlers].BlockHandler = blockHandler;
    handlers[numHandlers].WakeupHandler = wakeupHandler;
    handlers[numHandlers].blockData = blockData;
    handlers[numHandlers].deleted = FALSE;
    numHandlers = numHandlers + 1;
    return TRUE;
}

_X_EXPORT void
RemoveBlockAndWakeupHandlers (BlockHandlerProcPtr blockHandler, 
                              WakeupHandlerProcPtr wakeupHandler, 
                              pointer blockData)
{
    int     i;

    for (i = 0; i < numHandlers; i++)
        if (handlers[i].BlockHandler == blockHandler &&
            handlers[i].WakeupHandler == wakeupHandler &&
            handlers[i].blockData == blockData)
        {
            if (inHandler)
            {
                handlerDeleted = TRUE;
                handlers[i].deleted = TRUE;
            }
            else
            {
                for (; i < numHandlers - 1; i++)
                    handlers[i] = handlers[i+1];
                numHandlers--;
            }
            break;
        }
}

void
InitBlockAndWakeupHandlers (void)
{
    xfree (handlers);
    handlers = (BlockHandlerPtr) 0;
    numHandlers = 0;
    sizeHandlers = 0;
}

/*
 * A general work queue.  Perform some task before the server
 * sleeps for input.
 */

WorkQueuePtr            workQueue;
static WorkQueuePtr     *workQueueLast = &workQueue;

void
ProcessWorkQueue(void)
{
    WorkQueuePtr    q, *p;

    p = &workQueue;
    /*
     * Scan the work queue once, calling each function.  Those
     * which return TRUE are removed from the queue, otherwise
     * they will be called again.  This must be reentrant with
     * QueueWorkProc.
     */
    while ((q = *p))
    {
        if ((*q->function) (q->client, q->closure))
        {
            /* remove q from the list */
            *p = q->next;    /* don't fetch until after func called */
            xfree (q);
        }
        else
        {
            p = &q->next;    /* don't fetch until after func called */
        }
    }
    workQueueLast = p;
}

void
ProcessWorkQueueZombies(void)
{
    WorkQueuePtr    q, *p;

    p = &workQueue;
    while ((q = *p))
    {
        if (q->client && q->client->clientGone)
        {
            (void) (*q->function) (q->client, q->closure);
            /* remove q from the list */
            *p = q->next;    /* don't fetch until after func called */
            xfree (q);
        }
        else
        {
            p = &q->next;    /* don't fetch until after func called */
        }
    }
    workQueueLast = p;
}

_X_EXPORT Bool
QueueWorkProc (
    Bool (*function)(ClientPtr /* pClient */, pointer /* closure */),
    ClientPtr client, pointer closure)
{
    WorkQueuePtr    q;

    q = (WorkQueuePtr) xalloc (sizeof *q);
    if (!q)
        return FALSE;
    q->function = function;
    q->client = client;
    q->closure = closure;
    q->next = NULL;
    *workQueueLast = q;
    workQueueLast = &q->next;
    return TRUE;
}

/*
 * Manage a queue of sleeping clients, awakening them
 * when requested, by using the OS functions IgnoreClient
 * and AttendClient.  Note that this *ignores* the troubles
 * with request data interleaving itself with events, but
 * we'll leave that until a later time.
 */

typedef struct _SleepQueue {
    struct _SleepQueue  *next;
    ClientPtr           client;
    ClientSleepProcPtr  function;
    pointer             closure;
} SleepQueueRec, *SleepQueuePtr;

static SleepQueuePtr    sleepQueue = NULL;

_X_EXPORT Bool
ClientSleep (ClientPtr client, ClientSleepProcPtr function, pointer closure)
{
    SleepQueuePtr   q;

    q = (SleepQueuePtr) xalloc (sizeof *q);
    if (!q)
        return FALSE;

    IgnoreClient (client);
    q->next = sleepQueue;
    q->client = client;
    q->function = function;
    q->closure = closure;
    sleepQueue = q;
    return TRUE;
}

Bool
ClientSignal (ClientPtr client)
{
    SleepQueuePtr   q;

    for (q = sleepQueue; q; q = q->next)
        if (q->client == client)
        {
            return QueueWorkProc (q->function, q->client, q->closure);
        }
    return FALSE;
}

_X_EXPORT void
ClientWakeup (ClientPtr client)
{
    SleepQueuePtr   q, *prev;

    prev = &sleepQueue;
    while ( (q = *prev) )
    {
        if (q->client == client)
        {
            *prev = q->next;
            xfree (q);
            if (client->clientGone)
                /* Oops -- new zombie cleanup code ensures this only
                 * happens from inside CloseDownClient; don't want to
                 * recurse here...
                 */
                /* CloseDownClient(client) */;
            else
                AttendClient (client);
            break;
        }
        prev = &q->next;
    }
}

Bool
ClientIsAsleep (ClientPtr client)
{
    SleepQueuePtr   q;

    for (q = sleepQueue; q; q = q->next)
        if (q->client == client)
            return TRUE;
    return FALSE;
}

/*
 *  Generic Callback Manager
 */

/* ===== Private Procedures ===== */

static int numCallbackListsToCleanup = 0;
static CallbackListPtr **listsToCleanup = NULL;

static Bool 
_AddCallback(
    CallbackListPtr *pcbl,
    CallbackProcPtr callback,
    pointer         data)
{
    CallbackPtr     cbr;

    cbr = (CallbackPtr) xalloc(sizeof(CallbackRec));
    if (!cbr)
        return FALSE;
    cbr->proc = callback;
    cbr->data = data;
    cbr->next = (*pcbl)->list;
    cbr->deleted = FALSE;
    (*pcbl)->list = cbr;
    return TRUE;
}

static Bool 
_DeleteCallback(
    CallbackListPtr *pcbl,
    CallbackProcPtr callback,
    pointer         data)
{
    CallbackListPtr cbl = *pcbl;
    CallbackPtr     cbr, pcbr;

    for (pcbr = NULL, cbr = cbl->list;
         cbr != NULL;
         pcbr = cbr, cbr = cbr->next)
    {
        if ((cbr->proc == callback) && (cbr->data == data))
            break;
    }
    if (cbr != NULL)
    {
        if (cbl->inCallback)
        {
            ++(cbl->numDeleted);
            cbr->deleted = TRUE;
        }
        else
        {
            if (pcbr == NULL)
                cbl->list = cbr->next;
            else
                pcbr->next = cbr->next;
            xfree(cbr);
        }
        return TRUE;
    }
    return FALSE;
}

static void 
_CallCallbacks(
    CallbackListPtr    *pcbl,
    pointer         call_data)
{
    CallbackListPtr cbl = *pcbl;
    CallbackPtr     cbr, pcbr;

    ++(cbl->inCallback);
    for (cbr = cbl->list; cbr != NULL; cbr = cbr->next)
    {
        (*(cbr->proc)) (pcbl, cbr->data, call_data);
    }
    --(cbl->inCallback);

    if (cbl->inCallback) return;

    /* Was the entire list marked for deletion? */

    if (cbl->deleted)
    {
        DeleteCallbackList(pcbl);
        return;
    }

    /* Were some individual callbacks on the list marked for deletion?
     * If so, do the deletions.
     */

    if (cbl->numDeleted)
    {
        for (pcbr = NULL, cbr = cbl->list; (cbr != NULL) && cbl->numDeleted; )
        {
            if (cbr->deleted)
            {
                if (pcbr)
                {
                    cbr = cbr->next;
                    xfree(pcbr->next);
                    pcbr->next = cbr;
                } else
                {
                    cbr = cbr->next;
                    xfree(cbl->list);
                    cbl->list = cbr;
                }
                cbl->numDeleted--;
            }
            else /* this one wasn't deleted */
            {
                pcbr = cbr;
                cbr = cbr->next;
            }
        }
    }
}

static void
_DeleteCallbackList(
    CallbackListPtr    *pcbl)
{
    CallbackListPtr cbl = *pcbl;
    CallbackPtr     cbr, nextcbr;
    int i;

    if (cbl->inCallback)
    {
        cbl->deleted = TRUE;
        return;
    }

    for (i = 0; i < numCallbackListsToCleanup; i++)
    {
        if ((listsToCleanup[i] = pcbl) != 0)
        {
            listsToCleanup[i] = NULL;
            break;
        }
    }

    for (cbr = cbl->list; cbr != NULL; cbr = nextcbr)
    {
        nextcbr = cbr->next;
        xfree(cbr);
    }
    xfree(cbl);
    *pcbl = NULL;
}

static CallbackFuncsRec default_cbfuncs =
{
    _AddCallback,
    _DeleteCallback,
    _CallCallbacks,
    _DeleteCallbackList
};

static Bool
CreateCallbackList(CallbackListPtr *pcbl, CallbackFuncsPtr cbfuncs)
{
    CallbackListPtr  cbl;
    int i;

    if (!pcbl) return FALSE;
    cbl = (CallbackListPtr) xalloc(sizeof(CallbackListRec));
    if (!cbl) return FALSE;
    cbl->funcs = cbfuncs ? *cbfuncs : default_cbfuncs;
    cbl->inCallback = 0;
    cbl->deleted = FALSE;
    cbl->numDeleted = 0;
    cbl->list = NULL;
    *pcbl = cbl;

    for (i = 0; i < numCallbackListsToCleanup; i++)
    {
        if (!listsToCleanup[i])
        {
            listsToCleanup[i] = pcbl;
            return TRUE;
        }    
    }

    listsToCleanup = (CallbackListPtr **)xnfrealloc(listsToCleanup,
                sizeof(CallbackListPtr *) * (numCallbackListsToCleanup+1));
    listsToCleanup[numCallbackListsToCleanup] = pcbl;
    numCallbackListsToCleanup++;
    return TRUE;
}

/* ===== Public Procedures ===== */

_X_EXPORT Bool 
AddCallback(CallbackListPtr *pcbl, CallbackProcPtr callback, pointer data)
{
    if (!pcbl) return FALSE;
    if (!*pcbl)
    {   /* list hasn't been created yet; go create it */
        if (!CreateCallbackList(pcbl, (CallbackFuncsPtr)NULL))
            return FALSE;
    }
    return ((*(*pcbl)->funcs.AddCallback) (pcbl, callback, data));
}

_X_EXPORT Bool 
DeleteCallback(CallbackListPtr *pcbl, CallbackProcPtr callback, pointer data)
{
    if (!pcbl || !*pcbl) return FALSE;
    return ((*(*pcbl)->funcs.DeleteCallback) (pcbl, callback, data));
}

void 
CallCallbacks(CallbackListPtr *pcbl, pointer call_data)
{
    if (!pcbl || !*pcbl) return;
    (*(*pcbl)->funcs.CallCallbacks) (pcbl, call_data);
}

void
DeleteCallbackList(CallbackListPtr *pcbl)
{
    if (!pcbl || !*pcbl) return;
    (*(*pcbl)->funcs.DeleteCallbackList) (pcbl);
}

void 
InitCallbackManager(void)
{
    int i;

    for (i = 0; i < numCallbackListsToCleanup; i++)
    {
        DeleteCallbackList(listsToCleanup[i]);
    }
    if (listsToCleanup) xfree(listsToCleanup);

    numCallbackListsToCleanup = 0;
    listsToCleanup = NULL;
}