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/*

 * tkUnixXId.c --

 *

 *      This file provides a replacement function for the default X

 *      resource allocator (_XAllocID).  The problem with the default

 *      allocator is that it never re-uses ids, which causes long-lived

 *      applications to crash when X resource identifiers wrap around.

 *      The replacement functions in this file re-use old identifiers

 *      to prevent this problem.

 *

 *      The code in this file is based on similar implementations by

 *      George C. Kaplan and Michael Hoegeman.

 *

 * Copyright (c) 1993 The Regents of the University of California.

 * Copyright (c) 1994-1995 Sun Microsystems, Inc.

 *

 * See the file "license.terms" for information on usage and redistribution

 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.

 *

 * RCS: @(#) $Id: tkUnixXId.c,v 1.1.1.1 2002-01-16 10:26:02 markom Exp $

 */

/*

 * The definition below is needed on some systems so that we can access

 * the resource_alloc field of Display structures in order to replace

 * the resource allocator.

 */

#define XLIB_ILLEGAL_ACCESS 1

#include "tkInt.h"

#include "tkPort.h"

#include "tkUnixInt.h"

/*

 * A structure of the following type is used to hold one or more

 * available resource identifiers.  There is a list of these structures

 * for each display.

 */

#define IDS_PER_STACK 10

typedef struct TkIdStack {

    XID ids[IDS_PER_STACK];             /* Array of free identifiers. */

    int numUsed;                        /* Indicates how many of the entries

                                         * in ids are currently in use. */

    TkDisplay *dispPtr;                 /* Display to which ids belong. */

    struct TkIdStack *nextPtr;          /* Next bunch of free identifiers

                                         * for the same display. */

} TkIdStack;

/*

 * Forward declarations for procedures defined in this file:

 */

static XID              AllocXId _ANSI_ARGS_((Display *display));

static Tk_RestrictAction CheckRestrictProc _ANSI_ARGS_((

                            ClientData clientData, XEvent *eventPtr));

static void             WindowIdCleanup _ANSI_ARGS_((ClientData clientData));

static void             WindowIdCleanup2 _ANSI_ARGS_((ClientData clientData));

/*

 *----------------------------------------------------------------------

 *

 * TkInitXId --

 *

 *      This procedure is called to initialize the id allocator for

 *      a given display.

 *

 * Results:

 *      None.

 *

 * Side effects:

 *      The official allocator for the display is set up to be Tk_AllocXID.

 *

 *----------------------------------------------------------------------

 */

void

TkInitXId(dispPtr)

    TkDisplay *dispPtr;                 /* Tk's information about the

                                         * display. */

{

    dispPtr->idStackPtr = NULL;

    dispPtr->defaultAllocProc = (XID (*) _ANSI_ARGS_((Display *display)))

            dispPtr->display->resource_alloc;

    dispPtr->display->resource_alloc = AllocXId;

    dispPtr->windowStackPtr = NULL;

    dispPtr->idCleanupScheduled = 0;

}

/*

 *----------------------------------------------------------------------

 *

 * AllocXId --

 *

 *      This procedure is invoked by Xlib as the resource allocator

 *      for a display.

 *

 * Results:

 *      The return value is an X resource identifier that isn't currently

 *      in use.

 *

 * Side effects:

 *      The identifier is removed from the stack of free identifiers,

 *      if it was previously on the stack.

 *

 *----------------------------------------------------------------------

 */

static XID

AllocXId(display)

    Display *display;                   /* Display for which to allocate. */

{

    TkDisplay *dispPtr;

    TkIdStack *stackPtr;

    /*

     * Find Tk's information about the display.

     */

    dispPtr = TkGetDisplay(display);

    /*

     * If the topmost chunk on the stack is empty then free it.  Then

     * check for a free id on the stack and return it if it exists.

     */

    stackPtr = dispPtr->idStackPtr;

    if (stackPtr != NULL) {

        while (stackPtr->numUsed == 0) {

            dispPtr->idStackPtr = stackPtr->nextPtr;

            ckfree((char *) stackPtr);

            stackPtr = dispPtr->idStackPtr;

            if (stackPtr == NULL) {

                goto defAlloc;

            }

        }

        stackPtr->numUsed--;

        return stackPtr->ids[stackPtr->numUsed];

    }

    /*

     * No free ids in the stack:  just get one from the default

     * allocator.

     */

    defAlloc:

    return (*dispPtr->defaultAllocProc)(display);

}

/*

 *----------------------------------------------------------------------

 *

 * Tk_FreeXId --

 *

 *      This procedure is called to indicate that an X resource identifier

 *      is now free.

 *

 * Results:

 *      None.

 *

 * Side effects:

 *      The identifier is added to the stack of free identifiers for its

 *      display, so that it can be re-used.

 *

 *----------------------------------------------------------------------

 */

void

Tk_FreeXId(display, xid)

    Display *display;                   /* Display for which xid was

                                         * allocated. */

    XID xid;                            /* Identifier that is no longer

                                         * in use. */

{

    TkDisplay *dispPtr;

    TkIdStack *stackPtr;

    /*

     * Find Tk's information about the display.

     */

    dispPtr = TkGetDisplay(display);

    /*

     * Add a new chunk to the stack if the current chunk is full.

     */

    stackPtr = dispPtr->idStackPtr;

    if ((stackPtr == NULL) || (stackPtr->numUsed >= IDS_PER_STACK)) {

        stackPtr = (TkIdStack *) ckalloc(sizeof(TkIdStack));

        stackPtr->numUsed = 0;

        stackPtr->dispPtr = dispPtr;

        stackPtr->nextPtr = dispPtr->idStackPtr;

        dispPtr->idStackPtr = stackPtr;

    }

    /*

     * Add the id to the current chunk.

     */

    stackPtr->ids[stackPtr->numUsed] = xid;

    stackPtr->numUsed++;

}

/*

 *----------------------------------------------------------------------

 *

 * TkFreeWindowId --

 *

 *      This procedure is invoked instead of TkFreeXId for window ids.

 *      See below for the reason why.

 *

 * Results:

 *      None.

 *

 * Side effects:

 *      The id given by w will eventually be freed, so that it can be

 *      reused for other resources.

 *

 * Design:

 *      Freeing window ids is very tricky because there could still be

 *      events pending for a window in the event queue (or even in the

 *      server) at the time the window is destroyed.  If the window

 *      id were to get reused immediately for another window, old

 *      events could "drop in" on the new window, causing unexpected

 *      behavior.

 *

 *      Thus we have to wait to re-use a window id until we know that

 *      there are no events left for it.  Right now this is done in

 *      two steps.  First, we wait until we know that the server

 *      has seen the XDestroyWindow request, so we can be sure that

 *      it won't generate more events for the window and that any

 *      existing events are in our queue.  Second, we make sure that

 *      there are no events whatsoever in our queue (this is conservative

 *      but safe).

 *

 *      The first step is done by remembering the request id of the

 *      XDestroyWindow request and using LastKnownRequestProcessed to

 *      see what events the server has processed.  If multiple windows

 *      get destroyed at about the same time, we just remember the

 *      most recent request number for any of them (again, conservative

 *      but safe).

 *

 *      There are a few other complications as well.  When Tk destroys a

 *      sub-tree of windows, it only issues a single XDestroyWindow call,

 *      at the very end for the root of the subtree.  We can't free any of

 *      the window ids until the final XDestroyWindow call.  To make sure

 *      that this happens, we have to keep track of deletions in progress,

 *      hence the need for the "destroyCount" field of the display.

 *

 *      One final problem.  Some servers, like Sun X11/News servers still

 *      seem to have problems with ids getting reused too quickly.  I'm

 *      not completely sure why this is a problem, but delaying the

 *      recycling of ids appears to eliminate it.  Therefore, we wait

 *      an additional few seconds, even after "the coast is clear"

 *      before reusing the ids.

 *

 *----------------------------------------------------------------------

 */

void

TkFreeWindowId(dispPtr, w)

    TkDisplay *dispPtr;         /* Display that w belongs to. */

    Window w;                   /* X identifier for window on dispPtr. */

{

    TkIdStack *stackPtr;

    /*

     * Put the window id on a separate stack of window ids, rather

     * than the main stack, so it won't get reused right away.  Add

     * a new chunk to the stack if the current chunk is full.

     */

    stackPtr = dispPtr->windowStackPtr;

    if ((stackPtr == NULL) || (stackPtr->numUsed >= IDS_PER_STACK)) {

        stackPtr = (TkIdStack *) ckalloc(sizeof(TkIdStack));

        stackPtr->numUsed = 0;

        stackPtr->dispPtr = dispPtr;

        stackPtr->nextPtr = dispPtr->windowStackPtr;

        dispPtr->windowStackPtr = stackPtr;

    }

    /*

     * Add the id to the current chunk.

     */

    stackPtr->ids[stackPtr->numUsed] = w;

    stackPtr->numUsed++;

    /*

     * Schedule a call to WindowIdCleanup if one isn't already

     * scheduled.

     */

    if (!dispPtr->idCleanupScheduled) {

        dispPtr->idCleanupScheduled = 1;

        Tcl_CreateTimerHandler(100, WindowIdCleanup, (ClientData) dispPtr);

    }

}

/*

 *----------------------------------------------------------------------

 *

 * WindowIdCleanup --

 *

 *      See if we can now free up all the accumulated ids of

 *      deleted windows.

 *

 * Results:

 *      None.

 *

 * Side effects:

 *      If it's safe to move the window ids back to the main free

 *      list, we schedule this to happen after a few mores seconds

 *      of delay.  If it's not safe to move them yet, a timer handler

 *      gets invoked to try again later.

 *

 *----------------------------------------------------------------------

 */

static void

WindowIdCleanup(clientData)

    ClientData clientData;      /* Pointer to TkDisplay for display */

{

    TkDisplay *dispPtr = (TkDisplay *) clientData;

    int anyEvents, delta;

    Tk_RestrictProc *oldProc;

    ClientData oldData;

    static Tcl_Time timeout = {0, 0};

    dispPtr->idCleanupScheduled = 0;

    /*

     * See if it's safe to recycle the window ids.  It's safe if:

     * (a) no deletions are in progress.

     * (b) the server has seen all of the requests up to the last

     *     XDestroyWindow request.

     * (c) there are no events in the event queue; the only way to

     *     test for this right now is to create a restrict proc that

     *     will filter the events, then call Tcl_DoOneEvent to see if

     *     the procedure gets invoked.

     */

    if (dispPtr->destroyCount > 0) {

        goto tryAgain;

    }

    delta = LastKnownRequestProcessed(dispPtr->display)

            - dispPtr->lastDestroyRequest;

    if (delta < 0) {

        XSync(dispPtr->display, False);

    }

    anyEvents = 0;

    oldProc = Tk_RestrictEvents(CheckRestrictProc, (ClientData) &anyEvents,

            &oldData);

    TkUnixDoOneXEvent(&timeout);

    Tk_RestrictEvents(oldProc, oldData, &oldData);

    if (anyEvents) {

        goto tryAgain;

    }

    /*

     * These ids look safe to recycle, but we still need to delay a bit

     * more (see comments for TkFreeWindowId).  Schedule the final freeing.

     */

    if (dispPtr->windowStackPtr != NULL) {

        Tcl_CreateTimerHandler(5000, WindowIdCleanup2,

                (ClientData) dispPtr->windowStackPtr);

        dispPtr->windowStackPtr = NULL;

    }

    return;

    /*

     * It's still not safe to free up the ids.  Try again a bit later.

     */

    tryAgain:

    dispPtr->idCleanupScheduled = 1;

    Tcl_CreateTimerHandler(500, WindowIdCleanup, (ClientData) dispPtr);

}

/*

 *----------------------------------------------------------------------

 *

 * WindowIdCleanup2 --

 *

 *      This procedure is the last one in the chain that recycles

 *      window ids.  It takes all of the ids indicated by its

 *      argument and adds them back to the main id free list.

 *

 * Results:

 *      None.

 *

 * Side effects:

 *      Window ids get added to the main free list for their display.

 *

 *----------------------------------------------------------------------

 */

static void

WindowIdCleanup2(clientData)

    ClientData clientData;      /* Pointer to TkIdStack list. */

{

    TkIdStack *stackPtr = (TkIdStack *) clientData;

    TkIdStack *lastPtr;

    lastPtr = stackPtr;

    while (lastPtr->nextPtr != NULL) {

        lastPtr = lastPtr->nextPtr;

    }

    lastPtr->nextPtr = stackPtr->dispPtr->idStackPtr;

    stackPtr->dispPtr->idStackPtr = stackPtr;

}

/*

 *----------------------------------------------------------------------

 *

 * CheckRestrictProc --

 *

 *      This procedure is a restrict procedure, called by Tcl_DoOneEvent

 *      to filter X events.  All it does is to set a flag to indicate

 *      that there are X events present.

 *

 * Results:

 *      Sets the integer pointed to by the argument, then returns

 *      TK_DEFER_EVENT.

 *

 * Side effects:

 *      None.

 *

 *----------------------------------------------------------------------

 */

static Tk_RestrictAction

CheckRestrictProc(clientData, eventPtr)

    ClientData clientData;      /* Pointer to flag to set. */

    XEvent *eventPtr;           /* Event to filter;  not used. */

{

    int *flag = (int *) clientData;

    *flag = 1;

    return TK_DEFER_EVENT;

}

/*

 *----------------------------------------------------------------------

 *

 * Tk_GetPixmap --

 *

 *      Same as the XCreatePixmap procedure except that it manages

 *      resource identifiers better.

 *

 * Results:

 *      Returns a new pixmap.

 *

 * Side effects:

 *      None.

 *

 *----------------------------------------------------------------------

 */

Pixmap

Tk_GetPixmap(display, d, width, height, depth)

    Display *display;           /* Display for new pixmap. */

    Drawable d;                 /* Drawable where pixmap will be used. */

    int width, height;          /* Dimensions of pixmap. */

    int depth;                  /* Bits per pixel for pixmap. */

{

    return XCreatePixmap(display, d, (unsigned) width, (unsigned) height,

            (unsigned) depth);

}

/*

 *----------------------------------------------------------------------

 *

 * Tk_FreePixmap --

 *

 *      Same as the XFreePixmap procedure except that it also marks

 *      the resource identifier as free.

 *

 * Results:

 *      None.

 *

 * Side effects:

 *      The pixmap is freed in the X server and its resource identifier

 *      is saved for re-use.

 *

 *----------------------------------------------------------------------

 */

void

Tk_FreePixmap(display, pixmap)

    Display *display;           /* Display for which pixmap was allocated. */

    Pixmap pixmap;              /* Identifier for pixmap. */

{

    XFreePixmap(display, pixmap);

    Tk_FreeXId(display, (XID) pixmap);

}

/*

 *----------------------------------------------------------------------

 *

 * TkpWindowWasRecentlyDeleted --

 *

 *      Checks whether the window was recently deleted. This is called

 *      by the generic error handler to detect asynchronous notification

 *      of errors due to operations by Tk on a window that was already

 *      deleted by the server.

 *

 * Results:

 *      1 if the window was deleted recently, 0 otherwise.

 *

 * Side effects:

 *      None.

 *

 *----------------------------------------------------------------------

 */

int

TkpWindowWasRecentlyDeleted(win, dispPtr)

    Window win;         /* The window to check for. */

    TkDisplay *dispPtr; /* The window belongs to this display. */

{

    TkIdStack *stackPtr;

    int i;

    for (stackPtr = dispPtr->windowStackPtr;

         stackPtr != NULL;

         stackPtr = stackPtr->nextPtr) {

        for (i = 0; i < stackPtr->numUsed; i++) {

            if ((Window) stackPtr->ids[i] == win) {

                return 1;

            }

        }

    }

    return 0;

}