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tkGrab.c

/* 
 * tkGrab.c --
 *
 *    This file provides procedures that implement grabs for Tk.
 *
 * Copyright (c) 1992-1994 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: tkGrab.c,v 1.2 1998/09/14 18:23:11 stanton Exp $
 */

#include "tkPort.h"
#include "tkInt.h"

/*
 * The grab state machine has four states: ungrabbed, button pressed,
 * grabbed, and button pressed while grabbed.  In addition, there are
 * three pieces of grab state information: the current grab window,
 * the current restrict window, and whether the mouse is captured.
 *
 * The current grab window specifies the point in the Tk window
 * heirarchy above which pointer events will not be reported.  Any
 * window within the subtree below the grab window will continue to
 * receive events as normal.  Events outside of the grab tree will be
 * reported to the grab window.
 *
 * If the current restrict window is set, then all pointer events will
 * be reported only to the restrict window.  The restrict window is
 * normally set during an automatic button grab.
 *
 * The mouse capture state specifies whether the window system will
 * report mouse events outside of any Tk toplevels.  This is set
 * during a global grab or an automatic button grab.
 *
 * The transitions between different states is given in the following
 * table:
 * 
 * Event\State    U     B     G     GB
 * -----------    --    --    --    --
 * FirstPress     B     B     GB    GB
 * Press    B     B     G     GB
 * Release  U     B     G     GB
 * LastRelease    U     U     G     G
 * Grab           G     G     G     G
 * Ungrab   U     B     U     U
 *
 * Note: U=Ungrabbed, B=Button, G=Grabbed, GB=Grab and Button
 *
 * In addition, the following conditions are always true:
 *
 * State\Variable Grab       Restrict          Capture
 * -------------- ----       --------          -------
 * Ungrabbed             0          0           0
 * Button          0          1           1
 * Grabbed         1          0           b/g
 * Grab and Button       1          1           1
 *
 * Note: 0 means variable is set to NULL, 1 means variable is set to
 * some window, b/g means the variable is set to a window if a button
 * is currently down or a global grab is in effect.
 *
 * The final complication to all of this is enter and leave events.
 * In order to correctly handle all of the various cases, Tk cannot
 * rely on X enter/leave events in all situations.  The following
 * describes the correct sequence of enter and leave events that
 * should be observed by Tk scripts:
 *
 * Event(state)         Enter/Leave From -> To
 * ------------         ----------------------
 * LastRelease(B | GB): restrict window -> anc(grab window, event window)
 * Grab(U | B):   event window -> anc(grab window, event window)
 * Grab(G):       anc(old grab window, event window) ->
 *                      anc(new grab window, event window)
 * Grab(GB):            restrict window -> anc(new grab window, event window)
 * Ungrab(G):           anc(grab window, event window) -> event window
 * Ungrab(GB):          restrict window -> event window
 *
 * Note: anc(x,y) returns the least ancestor of y that is in the tree
 * of x, terminating at toplevels.
 */

/*
 * The following structure is used to pass information to 
 * GrabRestrictProc from EatGrabEvents.
 */

typedef struct {
    Display *display;         /* Display from which to discard events. */
    unsigned int serial;      /* Serial number with which to compare. */
} GrabInfo;

/*
 * Bit definitions for grabFlags field of TkDisplay structures:
 *
 * GRAB_GLOBAL                1 means this is a global grab (we grabbed via
 *                      the server so all applications are locked out).
 *                      0 means this is a local grab that affects
 *                      only this application.
 * GRAB_TEMP_GLOBAL           1 means we've temporarily grabbed via the
 *                      server because a button is down and we want
 *                      to make sure that we get the button-up
 *                      event.  The grab will be released when the
 *                      last mouse button goes up.
 */

#define GRAB_GLOBAL           1
#define GRAB_TEMP_GLOBAL      4

/*
 * The following structure is a Tcl_Event that triggers a change in
 * the grabWinPtr field of a display.  This event guarantees that
 * the change occurs in the proper order relative to enter and leave
 * events.
 */

typedef struct NewGrabWinEvent {
    Tcl_Event header;         /* Standard information for all Tcl events. */
    TkDisplay *dispPtr;       /* Display whose grab window is to change. */
    Window grabWindow;        /* New grab window for display.  This is
                         * recorded instead of a (TkWindow *) because
                         * it will allow us to detect cases where
                         * the window is destroyed before this event
                         * is processed. */
} NewGrabWinEvent;

/*
 * The following magic value is stored in the "send_event" field of
 * EnterNotify and LeaveNotify events that are generated in this
 * file.  This allows us to separate "real" events coming from the
 * server from those that we generated.
 */

#define GENERATED_EVENT_MAGIC ((Bool) 0x147321ac)

/*
 * Mask that selects any of the state bits corresponding to buttons,
 * plus masks that select individual buttons' bits:
 */

#define ALL_BUTTONS \
      (Button1Mask|Button2Mask|Button3Mask|Button4Mask|Button5Mask)
static unsigned int buttonStates[] = {
    Button1Mask, Button2Mask, Button3Mask, Button4Mask, Button5Mask
};

/*
 * Forward declarations for procedures declared later in this file:
 */

static void       EatGrabEvents _ANSI_ARGS_((TkDisplay *dispPtr,
                      unsigned int serial));
static TkWindow * FindCommonAncestor _ANSI_ARGS_((TkWindow *winPtr1,
                      TkWindow *winPtr2, int *countPtr1,
                      int *countPtr2));
static Tk_RestrictAction GrabRestrictProc _ANSI_ARGS_((ClientData arg,
                      XEvent *eventPtr));
static int        GrabWinEventProc _ANSI_ARGS_((Tcl_Event *evPtr,
                      int flags));
static void       MovePointer2 _ANSI_ARGS_((TkWindow *sourcePtr,
                      TkWindow *destPtr, int mode, int leaveEvents,
                      int EnterEvents));
static void       QueueGrabWindowChange _ANSI_ARGS_((TkDisplay *dispPtr,
                      TkWindow *grabWinPtr));
static void       ReleaseButtonGrab _ANSI_ARGS_((TkDisplay *dispPtr));

/*
 *----------------------------------------------------------------------
 *
 * Tk_GrabCmd --
 *
 *    This procedure is invoked to process the "grab" Tcl command.
 *    See the user documentation for details on what it does.
 *
 * Results:
 *    A standard Tcl result.
 *
 * Side effects:
 *    See the user documentation.
 *
 *----------------------------------------------------------------------
 */

      /* ARGSUSED */
int
Tk_GrabCmd(clientData, interp, argc, argv)
    ClientData clientData;    /* Main window associated with
                         * interpreter. */
    Tcl_Interp *interp;       /* Current interpreter. */
    int argc;                 /* Number of arguments. */
    char **argv;        /* Argument strings. */
{
    int globalGrab, c;
    Tk_Window tkwin;
    TkDisplay *dispPtr;
    size_t length;

    if (argc < 2) {
      badArgs:
      Tcl_AppendResult(interp, "wrong # args: should be \"",
            argv[0], " ?-global? window\" or \"", argv[0],
            " option ?arg arg ...?\"", (char *) NULL);
      return TCL_ERROR;
    }
    c = argv[1][0];
    length = strlen(argv[1]);
    if (c == '.') {
      if (argc != 2) {
          goto badArgs;
      }
      tkwin = Tk_NameToWindow(interp, argv[1], (Tk_Window) clientData);
      if (tkwin == NULL) {
          return TCL_ERROR;
      }
      return Tk_Grab(interp, tkwin, 0);
    } else if ((c == '-') && (strncmp(argv[1], "-global", length) == 0)
          && (length >= 2)) {
      if (argc != 3) {
          goto badArgs;
      }
      tkwin = Tk_NameToWindow(interp, argv[2], (Tk_Window) clientData);
      if (tkwin == NULL) {
          return TCL_ERROR;
      }
      return Tk_Grab(interp, tkwin, 1);
    } else if ((c == 'c') && (strncmp(argv[1], "current", length) == 0)) {
      if (argc > 3) {
          Tcl_AppendResult(interp, "wrong # args: should be \"",
                argv[0], " current ?window?\"", (char *) NULL);
          return TCL_ERROR;
      }
      if (argc == 3) {
          tkwin = Tk_NameToWindow(interp, argv[2], (Tk_Window) clientData);
          if (tkwin == NULL) {
            return TCL_ERROR;
          }
          dispPtr = ((TkWindow *) tkwin)->dispPtr;
          if (dispPtr->eventualGrabWinPtr != NULL) {
            interp->result = dispPtr->eventualGrabWinPtr->pathName;
          }
      } else {
          for (dispPtr = tkDisplayList; dispPtr != NULL;
                dispPtr = dispPtr->nextPtr) {
            if (dispPtr->eventualGrabWinPtr != NULL) {
                Tcl_AppendElement(interp,
                      dispPtr->eventualGrabWinPtr->pathName);
            }
          }
      }
      return TCL_OK;
    } else if ((c == 'r') && (strncmp(argv[1], "release", length) == 0)) {
      if (argc != 3) {
          Tcl_AppendResult(interp, "wrong # args: should be \"",
                argv[0], " release window\"", (char *) NULL);
          return TCL_ERROR;
      }
      tkwin = Tk_NameToWindow(interp, argv[2], (Tk_Window) clientData);
      if (tkwin == NULL) {
          Tcl_ResetResult(interp);
      } else {
          Tk_Ungrab(tkwin);
      }
    } else if ((c == 's') && (strncmp(argv[1], "set", length) == 0)
          && (length >= 2)) {
      if ((argc != 3) && (argc != 4)) {
          Tcl_AppendResult(interp, "wrong # args: should be \"",
                argv[0], " set ?-global? window\"", (char *) NULL);
          return TCL_ERROR;
      }
      if (argc == 3) {
          globalGrab = 0;
          tkwin = Tk_NameToWindow(interp, argv[2], (Tk_Window) clientData);
      } else {
          globalGrab = 1;
          length = strlen(argv[2]);
          if ((strncmp(argv[2], "-global", length) != 0) || (length < 2)) {
            Tcl_AppendResult(interp, "bad argument \"", argv[2],
                  "\": must be \"", argv[0], " set ?-global? window\"",
                  (char *) NULL);
            return TCL_ERROR;
          }
          tkwin = Tk_NameToWindow(interp, argv[3], (Tk_Window) clientData);
      }
      if (tkwin == NULL) {
          return TCL_ERROR;
      }
      return Tk_Grab(interp, tkwin, globalGrab);
    } else if ((c == 's') && (strncmp(argv[1], "status", length) == 0)
          && (length >= 2)) {
      TkWindow *winPtr;

      if (argc != 3) {
          Tcl_AppendResult(interp, "wrong # args: should be \"",
                argv[0], " status window\"", (char *) NULL);
          return TCL_ERROR;
      }
      winPtr = (TkWindow *) Tk_NameToWindow(interp, argv[2],
            (Tk_Window) clientData);
      if (winPtr == NULL) {
          return TCL_ERROR;
      }
      dispPtr = winPtr->dispPtr;
      if (dispPtr->eventualGrabWinPtr != winPtr) {
          interp->result = "none";
      } else if (dispPtr->grabFlags & GRAB_GLOBAL) {
          interp->result = "global";
      } else {
          interp->result = "local";
      }
    } else {
      Tcl_AppendResult(interp, "unknown or ambiguous option \"", argv[1],
            "\": must be current, release, set, or status",
            (char *) NULL);
      return TCL_ERROR;
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tk_Grab --
 *
 *    Grabs the pointer and keyboard, so that mouse-related events are
 *    only reported relative to a given window and its descendants.
 *
 * Results:
 *    A standard Tcl result is returned.  TCL_OK is the normal return
 *    value;  if the grab could not be set then TCL_ERROR is returned
 *    and interp->result will hold an error message.
 *
 * Side effects:
 *    Once this call completes successfully, no window outside the
 *    tree rooted at tkwin will receive pointer- or keyboard-related
 *    events until the next call to Tk_Ungrab.  If a previous grab was
 *    in effect within this application, then it is replaced with a new
 *    one.
 *
 *----------------------------------------------------------------------
 */

int
Tk_Grab(interp, tkwin, grabGlobal)
    Tcl_Interp *interp;             /* Used for error reporting. */
    Tk_Window tkwin;                /* Window on whose behalf the pointer
                               * is to be grabbed. */
    int grabGlobal;                 /* Non-zero means issue a grab to the
                               * server so that no other application
                               * gets mouse or keyboard events.
                               * Zero means the grab only applies
                               * within this application. */
{
    int grabResult, numTries;
    TkWindow *winPtr = (TkWindow *) tkwin;
    TkDisplay *dispPtr = winPtr->dispPtr;
    TkWindow *winPtr2;
    unsigned int serial;

    ReleaseButtonGrab(dispPtr);
    if (dispPtr->eventualGrabWinPtr != NULL) {
      if ((dispPtr->eventualGrabWinPtr == winPtr)
            && (grabGlobal == ((dispPtr->grabFlags & GRAB_GLOBAL) != 0))) {
          return TCL_OK;
      }
      if (dispPtr->eventualGrabWinPtr->mainPtr != winPtr->mainPtr) {
          alreadyGrabbed:
          interp->result = "grab failed: another application has grab";
          return TCL_ERROR;
      }
      Tk_Ungrab((Tk_Window) dispPtr->eventualGrabWinPtr);
    }

    Tk_MakeWindowExist(tkwin);
    if (!grabGlobal) {
      Window dummy1, dummy2;
      int dummy3, dummy4, dummy5, dummy6;
      unsigned int state;

      /*
       * Local grab.  However, if any mouse buttons are down, turn
       * it into a global grab temporarily, until the last button
       * goes up.  This does two things: (a) it makes sure that we
       * see the button-up event;  and (b) it allows us to track mouse
       * motion among all of the windows of this application.
       */

      dispPtr->grabFlags &= ~(GRAB_GLOBAL|GRAB_TEMP_GLOBAL);
      XQueryPointer(dispPtr->display, winPtr->window, &dummy1,
            &dummy2, &dummy3, &dummy4, &dummy5, &dummy6, &state);
      if ((state & ALL_BUTTONS) != 0) {
          dispPtr->grabFlags |= GRAB_TEMP_GLOBAL;
          goto setGlobalGrab;
      }
    } else {
      dispPtr->grabFlags |= GRAB_GLOBAL;
      setGlobalGrab:

      /*
       * Tricky point: must ungrab before grabbing.  This is needed
       * in case there is a button auto-grab already in effect.  If
       * there is, and the mouse has moved to a different window, X
       * won't generate enter and leave events to move the mouse if
       * we grab without ungrabbing.
       */

      XUngrabPointer(dispPtr->display, CurrentTime);
      serial = NextRequest(dispPtr->display);

      /*
       * Another tricky point: there are races with some window
       * managers that can cause grabs to fail because the window
       * manager hasn't released its grab quickly enough.  To work
       * around this problem, retry a few times after AlreadyGrabbed
       * errors to give the grab release enough time to register with
       * the server.
       */

      grabResult = 0;               /* Needed only to prevent gcc
                               * compiler warnings. */
      for (numTries = 0; numTries < 10; numTries++) {
          grabResult = XGrabPointer(dispPtr->display, winPtr->window,
                True, ButtonPressMask|ButtonReleaseMask|ButtonMotionMask
                |PointerMotionMask, GrabModeAsync, GrabModeAsync, None,
                None, CurrentTime);
          if (grabResult != AlreadyGrabbed) {
            break;
          }
          Tcl_Sleep(100);
      }
      if (grabResult != 0) {
          grabError:
          if (grabResult == GrabNotViewable) {
            interp->result = "grab failed: window not viewable";
          } else if (grabResult == AlreadyGrabbed) {
            goto alreadyGrabbed;
          } else if (grabResult == GrabFrozen) {
            interp->result = "grab failed: keyboard or pointer frozen";
          } else if (grabResult == GrabInvalidTime) {
            interp->result = "grab failed: invalid time";
          } else {
            char msg[100];
      
            sprintf(msg, "grab failed for unknown reason (code %d)",
                  grabResult);
            Tcl_AppendResult(interp, msg, (char *) NULL);
          }
          return TCL_ERROR;
      }
      grabResult = XGrabKeyboard(dispPtr->display, Tk_WindowId(tkwin),
            False, GrabModeAsync, GrabModeAsync, CurrentTime);
      if (grabResult != 0) {
          XUngrabPointer(dispPtr->display, CurrentTime);
          goto grabError;
      }

      /*
       * Eat up any grab-related events generated by the server for the
       * grab.  There are several reasons for doing this:
       *
       * 1. We have to synthesize the events for local grabs anyway, since
       *    the server doesn't participate in them.
       * 2. The server doesn't always generate the right events for global
       *    grabs (e.g. it generates events even if the current window is
       *    in the grab tree, which we don't want).
       * 3. We want all the grab-related events to be processed immediately
       *    (before other events that are already queued); events coming
       *    from the server will be in the wrong place, but events we
       *    synthesize here will go to the front of the queue.
       */

      EatGrabEvents(dispPtr, serial);
    }

    /*
     * Synthesize leave events to move the pointer from its current window
     * up to the lowest ancestor that it has in common with the grab window.
     * However, only do this if the pointer is outside the grab window's
     * subtree but inside the grab window's application.
     */

    if ((dispPtr->serverWinPtr != NULL)
          && (dispPtr->serverWinPtr->mainPtr == winPtr->mainPtr)) {
      for (winPtr2 = dispPtr->serverWinPtr; ; winPtr2 = winPtr2->parentPtr) {
          if (winPtr2 == winPtr) {
            break;
          }
          if (winPtr2 == NULL) {
            MovePointer2(dispPtr->serverWinPtr, winPtr, NotifyGrab, 1, 0);
            break;
          }
      }
    }
    QueueGrabWindowChange(dispPtr, winPtr);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tk_Ungrab --
 *
 *    Releases a grab on the mouse pointer and keyboard, if there
 *    is one set on the specified window.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    Pointer and keyboard events will start being delivered to other
 *    windows again.
 *
 *----------------------------------------------------------------------
 */

void
Tk_Ungrab(tkwin)
    Tk_Window tkwin;                /* Window whose grab should be
                               * released. */
{
    TkDisplay *dispPtr;
    TkWindow *grabWinPtr, *winPtr;
    unsigned int serial;

    grabWinPtr = (TkWindow *) tkwin;
    dispPtr = grabWinPtr->dispPtr;
    if (grabWinPtr != dispPtr->eventualGrabWinPtr) {
      return;
    }
    ReleaseButtonGrab(dispPtr);
    QueueGrabWindowChange(dispPtr, (TkWindow *) NULL);
    if (dispPtr->grabFlags & (GRAB_GLOBAL|GRAB_TEMP_GLOBAL)) {
      dispPtr->grabFlags &= ~(GRAB_GLOBAL|GRAB_TEMP_GLOBAL);
      serial = NextRequest(dispPtr->display);
      XUngrabPointer(dispPtr->display, CurrentTime);
      XUngrabKeyboard(dispPtr->display, CurrentTime);
      EatGrabEvents(dispPtr, serial);
    }

    /*
     * Generate events to move the pointer back to the window where it
     * really is.  Some notes:
     * 1. As with grabs, only do this if the "real" window is not a
     *    descendant of the grab window, since in this case the pointer
     *    is already where it's supposed to be.
     * 2. If the "real" window is in some other application then don't
     *    generate any events at all, since everything's already been
     *    reported correctly.
     * 3. Only generate enter events.  Don't generate leave events,
     *    because we never told the lower-level windows that they
     *    had the pointer in the first place.
     */

    for (winPtr = dispPtr->serverWinPtr; ; winPtr = winPtr->parentPtr) {
      if (winPtr == grabWinPtr) {
          break;
      }
      if (winPtr == NULL) {
          if ((dispPtr->serverWinPtr == NULL) ||
                (dispPtr->serverWinPtr->mainPtr == grabWinPtr->mainPtr)) {
            MovePointer2(grabWinPtr, dispPtr->serverWinPtr,
                  NotifyUngrab, 0, 1);
          }
          break;
      }
    }
}

/*
 *----------------------------------------------------------------------
 *
 * ReleaseButtonGrab --
 *
 *    This procedure is called to release a simulated button grab, if
 *    there is one in effect.  A button grab is present whenever
 *    dispPtr->buttonWinPtr is non-NULL or when the GRAB_TEMP_GLOBAL
 *    flag is set.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    DispPtr->buttonWinPtr is reset to NULL, and enter and leave
 *    events are generated if necessary to move the pointer from
 *    the button grab window to its current window.
 *
 *----------------------------------------------------------------------
 */

static void
ReleaseButtonGrab(dispPtr)
    register TkDisplay *dispPtr;    /* Display whose button grab is to be
                               * released. */
{
    unsigned int serial;

    if (dispPtr->buttonWinPtr != NULL) {
      if (dispPtr->buttonWinPtr != dispPtr->serverWinPtr) {
          MovePointer2(dispPtr->buttonWinPtr, dispPtr->serverWinPtr,
                NotifyUngrab, 1, 1);
      }
      dispPtr->buttonWinPtr = NULL;
    }
    if (dispPtr->grabFlags & GRAB_TEMP_GLOBAL) {
      dispPtr->grabFlags &= ~GRAB_TEMP_GLOBAL;
      serial = NextRequest(dispPtr->display);
      XUngrabPointer(dispPtr->display, CurrentTime);
      XUngrabKeyboard(dispPtr->display, CurrentTime);
      EatGrabEvents(dispPtr, serial);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * TkPointerEvent --
 *
 *    This procedure is called for each pointer-related event, before
 *    the event has been processed.  It does various things to make
 *    grabs work correctly.
 *
 * Results:
 *    If the return value is 1 it means the event should be processed
 *    (event handlers should be invoked).  If the return value is 0
 *    it means the event should be ignored in order to make grabs
 *    work correctly.  In some cases this procedure modifies the event.
 *
 * Side effects:
 *    Grab state information may be updated.  New events may also be
 *    pushed back onto the event queue to replace or augment the
 *    one passed in here.
 *
 *----------------------------------------------------------------------
 */

int
TkPointerEvent(eventPtr, winPtr)
    register XEvent *eventPtr;            /* Pointer to the event. */
    TkWindow *winPtr;               /* Tk's information for window
                               * where event was reported. */
{
    register TkWindow *winPtr2;
    TkDisplay *dispPtr = winPtr->dispPtr;
    unsigned int serial;
    int outsideGrabTree = 0;
    int ancestorOfGrab = 0;
    int appGrabbed = 0;             /* Non-zero means event is being
                               * reported to an application that is
                               * affected by the grab. */

    /*
     * Collect information about the grab (if any).
     */

    switch (TkGrabState(winPtr)) {
      case TK_GRAB_IN_TREE:
          appGrabbed = 1;
          break;
      case TK_GRAB_ANCESTOR:
          appGrabbed = 1;
          outsideGrabTree = 1;
          ancestorOfGrab = 1;
          break;
      case TK_GRAB_EXCLUDED:
          appGrabbed = 1;
          outsideGrabTree = 1;
          break;
    }

    if ((eventPtr->type == EnterNotify) || (eventPtr->type == LeaveNotify)) {
      /*
       * Keep track of what window the mouse is *really* over.
       * Any events that we generate have a special send_event value,
       * which is detected below and used to ignore the event for
       * purposes of setting serverWinPtr.
       */

      if (eventPtr->xcrossing.send_event != GENERATED_EVENT_MAGIC) {
          if ((eventPtr->type == LeaveNotify) &&
                (winPtr->flags & TK_TOP_LEVEL)) {
            dispPtr->serverWinPtr = NULL;
          } else {
            dispPtr->serverWinPtr = winPtr;
          }
      }

      /*
       * When a grab is active, X continues to report enter and leave
       * events for windows outside the tree of the grab window:
       * 1. Detect these events and ignore them except for
       *    windows above the grab window.
       * 2. Allow Enter and Leave events to pass through the
       *    windows above the grab window, but never let them
       *    end up with the pointer *in* one of those windows.
       */

      if (dispPtr->grabWinPtr != NULL) {
          if (outsideGrabTree && appGrabbed) {
            if (!ancestorOfGrab) {
                return 0;
            }
            switch (eventPtr->xcrossing.detail) {
                case NotifyInferior:
                  return 0;
                case NotifyAncestor:
                  eventPtr->xcrossing.detail = NotifyVirtual;
                  break;
                case NotifyNonlinear:
                  eventPtr->xcrossing.detail = NotifyNonlinearVirtual;
                  break;
            }
          }

          /*
           * Make buttons have the same grab-like behavior inside a grab
           * as they do outside a grab:  do this by ignoring enter and
           * leave events except for the window in which the button was
           * pressed.
           */

          if ((dispPtr->buttonWinPtr != NULL)
                && (winPtr != dispPtr->buttonWinPtr)) {
            return 0;
          }
      }
      return 1;
    }

    if (!appGrabbed) {
      return 1;
    }

    if (eventPtr->type == MotionNotify) {
      /*
       * When grabs are active, X reports motion events relative to the
       * window under the pointer.  Instead, it should report the events
       * relative to the window the button went down in, if there is a
       * button down.  Otherwise, if the pointer window is outside the
       * subtree of the grab window, the events should be reported
       * relative to the grab window.  Otherwise, the event should be
       * reported to the pointer window.
       */

      winPtr2 = winPtr;
      if (dispPtr->buttonWinPtr != NULL) {
          winPtr2 = dispPtr->buttonWinPtr;
      } else if (outsideGrabTree || (dispPtr->serverWinPtr == NULL)) {
          winPtr2 = dispPtr->grabWinPtr;
      }
      if (winPtr2 != winPtr) {
          TkChangeEventWindow(eventPtr, winPtr2);
          Tk_QueueWindowEvent(eventPtr, TCL_QUEUE_HEAD);
          return 0;
      }
      return 1;
    }

    /*
     * Process ButtonPress and ButtonRelease events:
     * 1. Keep track of whether a button is down and what window it
     *    went down in.
     * 2. If the first button goes down outside the grab tree, pretend
     *    it went down in the grab window.  Note: it's important to
     *    redirect events to the grab window like this in order to make
     *    things like menus work, where button presses outside the
     *    grabbed menu need to be seen.  An application can always
     *    ignore the events if they occur outside its window.
     * 3. If a button press or release occurs outside the window where
     *    the first button was pressed, retarget the event so it's reported
     *    to the window where the first button was pressed.
     * 4. If the last button is released in a window different than where
     *    the first button was pressed, generate Enter/Leave events to
     *    move the mouse from the button window to its current window.
     * 5. If the grab is set at a time when a button is already down, or
     *    if the window where the button was pressed was deleted, then
     *    dispPtr->buttonWinPtr will stay NULL.  Just forget about the
     *    auto-grab for the button press;  events will go to whatever
     *    window contains the pointer.  If this window isn't in the grab
     *    tree then redirect events to the grab window.
     * 6. When a button is pressed during a local grab, the X server sets
     *    a grab of its own, since it doesn't even know about our local
     *    grab.  This causes enter and leave events no longer to be
     *    generated in the same way as for global grabs.  To eliminate this
     *    problem, set a temporary global grab when the first button goes
     *    down and release it when the last button comes up.
     */

    if ((eventPtr->type == ButtonPress) || (eventPtr->type == ButtonRelease)) {
      winPtr2 = dispPtr->buttonWinPtr;
      if (winPtr2 == NULL) {
          if (outsideGrabTree) {
            winPtr2 = dispPtr->grabWinPtr;                  /* Note 5. */
          } else {
            winPtr2 = winPtr;                   /* Note 5. */
          }
      }
      if (eventPtr->type == ButtonPress) {
          if ((eventPtr->xbutton.state & ALL_BUTTONS) == 0) {
            if (outsideGrabTree) {
                TkChangeEventWindow(eventPtr, dispPtr->grabWinPtr);
                Tk_QueueWindowEvent(eventPtr, TCL_QUEUE_HEAD);
                return 0;                             /* Note 2. */
            }
            if (!(dispPtr->grabFlags & GRAB_GLOBAL)) {      /* Note 6. */
                serial = NextRequest(dispPtr->display);
                if (XGrabPointer(dispPtr->display,
                      dispPtr->grabWinPtr->window, True,
                      ButtonPressMask|ButtonReleaseMask|ButtonMotionMask,
                      GrabModeAsync, GrabModeAsync, None, None,
                      CurrentTime) == 0) {
                  EatGrabEvents(dispPtr, serial);
                  if (XGrabKeyboard(dispPtr->display, winPtr->window,
                        False, GrabModeAsync, GrabModeAsync,
                        CurrentTime) == 0) {
                      dispPtr->grabFlags |= GRAB_TEMP_GLOBAL;
                  } else {
                      XUngrabPointer(dispPtr->display, CurrentTime);
                  }
                }
            }
            dispPtr->buttonWinPtr = winPtr;
            return 1;
          }
      } else {
          if ((eventPtr->xbutton.state & ALL_BUTTONS)
                == buttonStates[eventPtr->xbutton.button - Button1]) {
            ReleaseButtonGrab(dispPtr);               /* Note 4. */
          }
      }
      if (winPtr2 != winPtr) {
          TkChangeEventWindow(eventPtr, winPtr2);
          Tk_QueueWindowEvent(eventPtr, TCL_QUEUE_HEAD);
          return 0;                                   /* Note 3. */
      }
    }

    return 1;
}

/*
 *----------------------------------------------------------------------
 *
 * TkChangeEventWindow --
 *
 *    Given an event and a new window to which the event should be
 *    retargeted, modify fields of the event so that the event is
 *    properly retargeted to the new window.
 *
 * Results:
 *    The following fields of eventPtr are modified:  window,
 *    subwindow, x, y, same_screen.
 *
 * Side effects:
 *    None.
 *
 *----------------------------------------------------------------------
 */

void
TkChangeEventWindow(eventPtr, winPtr)
    register XEvent *eventPtr;      /* Event to retarget.  Must have
                         * type ButtonPress, ButtonRelease, KeyPress,
                         * KeyRelease, MotionNotify, EnterNotify,
                         * or LeaveNotify. */
    TkWindow *winPtr;         /* New target window for event. */
{
    int x, y, sameScreen, bd;
    register TkWindow *childPtr;

    eventPtr->xmotion.window = Tk_WindowId(winPtr);
    if (eventPtr->xmotion.root ==
          RootWindow(winPtr->display, winPtr->screenNum)) {
      Tk_GetRootCoords((Tk_Window) winPtr, &x, &y);
      eventPtr->xmotion.x = eventPtr->xmotion.x_root - x;
      eventPtr->xmotion.y = eventPtr->xmotion.y_root - y;
      eventPtr->xmotion.subwindow = None;
      for (childPtr = winPtr->childList; childPtr != NULL;
            childPtr = childPtr->nextPtr) {
          if (childPtr->flags & TK_TOP_LEVEL) {
            continue;
          }
          x = eventPtr->xmotion.x - childPtr->changes.x;
          y = eventPtr->xmotion.y - childPtr->changes.y;
          bd = childPtr->changes.border_width;
          if ((x >= -bd) && (y >= -bd)
                && (x < (childPtr->changes.width + bd))
                && (y < (childPtr->changes.height + bd))) {
            eventPtr->xmotion.subwindow = childPtr->window;
          }
      }
      sameScreen = 1;
    } else {
      eventPtr->xmotion.x = 0;
      eventPtr->xmotion.y = 0;
      eventPtr->xmotion.subwindow = None;
      sameScreen = 0;
    }
    if (eventPtr->type == MotionNotify) {
      eventPtr->xmotion.same_screen = sameScreen;
    } else {
      eventPtr->xbutton.same_screen = sameScreen;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * TkInOutEvents --
 *
 *    This procedure synthesizes EnterNotify and LeaveNotify events
 *    to correctly transfer the pointer from one window to another.
 *    It can also be used to generate FocusIn and FocusOut events
 *    to move the input focus.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    Synthesized events may be pushed back onto the event queue.
 *    The event pointed to by eventPtr is modified.
 *
 *----------------------------------------------------------------------
 */

void
TkInOutEvents(eventPtr, sourcePtr, destPtr, leaveType, enterType, position)
    XEvent *eventPtr;         /* A template X event.  Must have all fields
                         * properly set except for type, window,
                         * subwindow, x, y, detail, and same_screen
                         * (Not all of these fields are valid for
                         * FocusIn/FocusOut events;  x_root and y_root
                         * must be valid for Enter/Leave events, even
                         * though x and y needn't be valid). */
    TkWindow *sourcePtr;      /* Window that used to have the pointer or
                         * focus (NULL means it was not in a window
                         * managed by this process). */
    TkWindow *destPtr;        /* Window that is to end up with the pointer
                         * or focus (NULL means it's not one managed
                         * by this process). */
    int leaveType;            /* Type of events to generate for windows
                         * being left (LeaveNotify or FocusOut).  0
                         * means don't generate leave events. */
    int enterType;            /* Type of events to generate for windows
                         * being entered (EnterNotify or FocusIn).  0
                         * means don't generate enter events. */
    Tcl_QueuePosition position;     /* Position at which events are added to
                         * the system event queue. */
{
    register TkWindow *winPtr;
    int upLevels, downLevels, i, j, focus;

    /*
     * There are four possible cases to deal with:
     *
     * 1. SourcePtr and destPtr are the same.  There's nothing to do in
     *    this case.
     * 2. SourcePtr is an ancestor of destPtr in the same top-level
     *    window.  Must generate events down the window tree from source
     *    to dest.
     * 3. DestPtr is an ancestor of sourcePtr in the same top-level
     *    window.  Must generate events up the window tree from sourcePtr
     *    to destPtr.
     * 4. All other cases.  Must first generate events up the window tree
     *    from sourcePtr to its top-level, then down from destPtr's
     *    top-level to destPtr. This form is called "non-linear."
     *
     * The call to FindCommonAncestor separates these four cases and decides
     * how many levels up and down events have to be generated for.
     */

    if (sourcePtr == destPtr) {
      return;
    }
    if ((leaveType == FocusOut) || (enterType == FocusIn)) {
      focus = 1;
    } else {
      focus = 0;
    }
    FindCommonAncestor(sourcePtr, destPtr, &upLevels, &downLevels);

    /*
     * Generate enter/leave events and add them to the grab event queue.
     */


#define QUEUE(w, t, d)                          \
    if (w->window != None) {                    \
      eventPtr->type = t;                       \
      if (focus) {                              \
          eventPtr->xfocus.window = w->window;  \
          eventPtr->xfocus.detail = d;          \
      } else {                            \
          eventPtr->xcrossing.detail = d;       \
          TkChangeEventWindow(eventPtr, w);           \
      }                                   \
      Tk_QueueWindowEvent(eventPtr, position);  \
    }

    if (downLevels == 0) {
    
      /*
       * SourcePtr is an inferior of destPtr.
       */

      if (leaveType != 0) {
          QUEUE(sourcePtr, leaveType, NotifyAncestor);
          for (winPtr = sourcePtr->parentPtr, i = upLevels-1; i > 0;
                winPtr = winPtr->parentPtr, i--) {
            QUEUE(winPtr, leaveType, NotifyVirtual);
          }
      }
      if ((enterType != 0) && (destPtr != NULL)) {
          QUEUE(destPtr, enterType, NotifyInferior);
      }
    } else if (upLevels == 0) {

      /*
       * DestPtr is an inferior of sourcePtr.
       */

      if ((leaveType != 0) && (sourcePtr != NULL)) {
          QUEUE(sourcePtr, leaveType, NotifyInferior);
      }
      if (enterType != 0) {
          for (i = downLevels-1; i > 0; i--) {
            for (winPtr = destPtr->parentPtr, j = 1; j < i;
                  winPtr = winPtr->parentPtr, j++) {
            }
            QUEUE(winPtr, enterType, NotifyVirtual);
          }
          if (destPtr != NULL) {
            QUEUE(destPtr, enterType, NotifyAncestor);
          }
      }
    } else {

      /*
       * Non-linear:  neither window is an inferior of the other.
       */

      if (leaveType != 0) {
          QUEUE(sourcePtr, leaveType, NotifyNonlinear);
          for (winPtr = sourcePtr->parentPtr, i = upLevels-1; i > 0;
                winPtr = winPtr->parentPtr, i--) {
            QUEUE(winPtr, leaveType, NotifyNonlinearVirtual);
          }
      }
      if (enterType != 0) {
          for (i = downLevels-1; i > 0; i--) {
            for (winPtr = destPtr->parentPtr, j = 1; j < i;
                  winPtr = winPtr->parentPtr, j++) {
            }
            QUEUE(winPtr, enterType, NotifyNonlinearVirtual);
          }
          if (destPtr != NULL) {
            QUEUE(destPtr, enterType, NotifyNonlinear);
          }
      }
    }
}

/*
 *----------------------------------------------------------------------
 *
 * MovePointer2 --
 *
 *    This procedure synthesizes  EnterNotify and LeaveNotify events
 *    to correctly transfer the pointer from one window to another.
 *    It is different from TkInOutEvents in that no template X event
 *    needs to be supplied;  this procedure generates the template
 *    event and calls TkInOutEvents.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    Synthesized events may be pushed back onto the event queue.
 *
 *----------------------------------------------------------------------
 */

static void
MovePointer2(sourcePtr, destPtr, mode, leaveEvents, enterEvents)
    TkWindow *sourcePtr;      /* Window currently containing pointer (NULL
                         * means it's not one managed by this
                         * process). */
    TkWindow *destPtr;        /* Window that is to end up containing the
                         * pointer (NULL means it's not one managed
                         * by this process). */
    int mode;                 /* Mode for enter/leave events, such as
                         * NotifyNormal or NotifyUngrab. */
    int leaveEvents;          /* Non-zero means generate leave events for the
                         * windows being left.  Zero means don't
                         * generate leave events. */
    int enterEvents;          /* Non-zero means generate enter events for the
                         * windows being entered.  Zero means don't
                         * generate enter events. */
{
    XEvent event;
    Window dummy1, dummy2;
    int dummy3, dummy4;
    TkWindow *winPtr;

    winPtr = sourcePtr;
    if ((winPtr == NULL) || (winPtr->window == None)) {
      winPtr = destPtr;
      if ((winPtr == NULL) || (winPtr->window == None)) {
          return;
      }
    }

    event.xcrossing.serial = LastKnownRequestProcessed(
      winPtr->display);
    event.xcrossing.send_event = GENERATED_EVENT_MAGIC;
    event.xcrossing.display = winPtr->display;
    event.xcrossing.root = RootWindow(winPtr->display,
          winPtr->screenNum);
    event.xcrossing.time = TkCurrentTime(winPtr->dispPtr);
    XQueryPointer(winPtr->display, winPtr->window, &dummy1, &dummy2,
          &event.xcrossing.x_root, &event.xcrossing.y_root,
          &dummy3, &dummy4, &event.xcrossing.state);
    event.xcrossing.mode = mode;
    event.xcrossing.focus = False;
    TkInOutEvents(&event, sourcePtr, destPtr, (leaveEvents) ? LeaveNotify : 0,
          (enterEvents) ? EnterNotify : 0, TCL_QUEUE_MARK);
}

/*
 *----------------------------------------------------------------------
 *
 * TkGrabDeadWindow --
 *
 *    This procedure is invoked whenever a window is deleted, so that
 *    grab-related cleanup can be performed.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    Various cleanups happen, such as generating events to move the
 *    pointer back to its "natural" window as if an ungrab had been
 *    done.  See the code.
 *
 *----------------------------------------------------------------------
 */

void
TkGrabDeadWindow(winPtr)
    register TkWindow *winPtr;            /* Window that is in the process
                               * of being deleted. */
{
    TkDisplay *dispPtr = winPtr->dispPtr;

    if (dispPtr->eventualGrabWinPtr == winPtr) {
      /*
       * Grab window was deleted.  Release the grab.
       */

      Tk_Ungrab((Tk_Window) dispPtr->eventualGrabWinPtr);
    } else if (dispPtr->buttonWinPtr == winPtr) {
      ReleaseButtonGrab(dispPtr);
    }
    if (dispPtr->serverWinPtr == winPtr) {
      if (winPtr->flags & TK_TOP_LEVEL) {
          dispPtr->serverWinPtr = NULL;
      } else {
          dispPtr->serverWinPtr = winPtr->parentPtr;
      }
    }
    if (dispPtr->grabWinPtr == winPtr) {
      dispPtr->grabWinPtr = NULL;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * EatGrabEvents --
 *
 *    This procedure is called to eliminate any Enter, Leave,
 *    FocusIn, or FocusOut events in the event queue for a
 *    display that have mode NotifyGrab or NotifyUngrab and
 *    have a serial number no less than a given value and are not
 *    generated by the grab module.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    DispPtr's display gets sync-ed, and some of the events get
 *    removed from the Tk event queue.
 *
 *----------------------------------------------------------------------
 */

static void
EatGrabEvents(dispPtr, serial)
    TkDisplay *dispPtr;       /* Display from which to consume events. */
    unsigned int serial;      /* Only discard events that have a serial
                         * number at least this great. */
{
    Tk_RestrictProc *oldProc;
    GrabInfo info;
    ClientData oldArg, dummy;

    info.display = dispPtr->display;
    info.serial = serial;
    TkpSync(info.display);
    oldProc = Tk_RestrictEvents(GrabRestrictProc, (ClientData)&info, &oldArg);
    while (Tcl_ServiceEvent(TCL_WINDOW_EVENTS)) {
    }
    Tk_RestrictEvents(oldProc, oldArg, &dummy);
}

/*
 *----------------------------------------------------------------------
 *
 * GrabRestrictProc --
 *
 *    A Tk_RestrictProc used by EatGrabEvents to eliminate any
 *    Enter, Leave, FocusIn, or FocusOut events in the event queue
 *    for a display that has mode NotifyGrab or NotifyUngrab and
 *    have a serial number no less than a given value.
 *
 * Results:
 *    Returns either TK_DISCARD_EVENT or TK_DEFER_EVENT.
 *
 * Side effects:
 *    None.
 *
 *----------------------------------------------------------------------
 */

static Tk_RestrictAction
GrabRestrictProc(arg, eventPtr)
    ClientData arg;
    XEvent *eventPtr;
{
    GrabInfo *info = (GrabInfo *) arg;
    int mode, diff;

    /*
     * The diff caculation is trickier than it may seem.  Don't forget
     * that serial numbers can wrap around, so can't compare the two
     * serial numbers directly.
     */

    diff = eventPtr->xany.serial - info->serial;
    if ((eventPtr->type == EnterNotify)
          || (eventPtr->type == LeaveNotify)) {
      mode = eventPtr->xcrossing.mode;
    } else if ((eventPtr->type == FocusIn)
          || (eventPtr->type == FocusOut)) {
      mode = eventPtr->xfocus.mode;
    } else {
      mode = NotifyNormal;
    }
    if ((info->display != eventPtr->xany.display) || (mode == NotifyNormal)
          || (diff < 0)) {
      return TK_DEFER_EVENT;
    } else {
      return TK_DISCARD_EVENT;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * QueueGrabWindowChange --
 *
 *    This procedure queues a special event in the Tcl event queue,
 *    which will cause the "grabWinPtr" field for the display to get
 *    modified when the event is processed.  This is needed to make
 *    sure that the grab window changes at the proper time relative
 *    to grab-related enter and leave events that are also in the
 *    queue.  In particular, this approach works even when multiple
 *    grabs and ungrabs happen back-to-back.
 *
 * Results:
 *    None.
 *
 * Side effects:
 *    DispPtr->grabWinPtr will be modified later (by GrabWinEventProc)
 *    when the event is removed from the grab event queue.
 *
 *----------------------------------------------------------------------
 */

static void
QueueGrabWindowChange(dispPtr, grabWinPtr)
    TkDisplay *dispPtr;       /* Display on which to change the grab
                         * window. */
    TkWindow *grabWinPtr;     /* Window that is to become the new grab
                         * window (may be NULL). */
{
    NewGrabWinEvent *grabEvPtr;

    grabEvPtr = (NewGrabWinEvent *) ckalloc(sizeof(NewGrabWinEvent));
    grabEvPtr->header.proc = GrabWinEventProc;
    grabEvPtr->dispPtr = dispPtr;
    if (grabWinPtr == NULL) {
      grabEvPtr->grabWindow = None;
    } else {
      grabEvPtr->grabWindow = grabWinPtr->window;
    }
    Tcl_QueueEvent(&grabEvPtr->header, TCL_QUEUE_MARK);
    dispPtr->eventualGrabWinPtr = grabWinPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * GrabWinEventProc --
 *
 *    This procedure is invoked as a handler for Tcl_Events of type
 *    NewGrabWinEvent.  It updates the current grab window field in
 *    a display.
 *
 * Results:
 *    Returns 1 if the event was processed, 0 if it should be deferred
 *    for processing later.
 *
 * Side effects:
 *    The grabWinPtr field is modified in the display associated with
 *    the event.
 *
 *----------------------------------------------------------------------
 */

static int
GrabWinEventProc(evPtr, flags)
    Tcl_Event *evPtr;         /* Event of type NewGrabWinEvent. */
    int flags;                /* Flags argument to Tk_DoOneEvent: indicates
                         * what kinds of events are being processed
                         * right now. */
{
    NewGrabWinEvent *grabEvPtr = (NewGrabWinEvent *) evPtr;

    grabEvPtr->dispPtr->grabWinPtr = (TkWindow *) Tk_IdToWindow(
          grabEvPtr->dispPtr->display, grabEvPtr->grabWindow);
    return 1;
}

/*
 *----------------------------------------------------------------------
 *
 * FindCommonAncestor --
 *
 *    Given two windows, this procedure finds their least common
 *    ancestor and also computes how many levels up this ancestor
 *    is from each of the original windows.
 *
 * Results:
 *    If the windows are in different applications or top-level
 *    windows, then NULL is returned and *countPtr1 and *countPtr2
 *    are set to the depths of the two windows in their respective
 *    top-level windows (1 means the window is a top-level, 2 means
 *    its parent is a top-level, and so on).  Otherwise, the return
 *    value is a pointer to the common ancestor and the counts are
 *    set to the distance of winPtr1 and winPtr2 from this ancestor
 *    (1 means they're children, 2 means grand-children, etc.).
 *
 * Side effects:
 *    None.
 *
 *----------------------------------------------------------------------
 */

static TkWindow *
FindCommonAncestor(winPtr1, winPtr2, countPtr1, countPtr2)
    TkWindow *winPtr1;        /* First window.   May be NULL. */
    TkWindow *winPtr2;        /* Second window.  May be NULL. */
    int *countPtr1;           /* Store nesting level of winPtr1 within
                         * common ancestor here. */
    int *countPtr2;           /* Store nesting level of winPtr2 within
                         * common ancestor here. */
{
    register TkWindow *winPtr;
    TkWindow *ancestorPtr;
    int count1, count2, i;

    /*
     * Mark winPtr1 and all of its ancestors with a special flag bit.
     */

    if (winPtr1 != NULL) {
      for (winPtr = winPtr1; winPtr != NULL; winPtr = winPtr->parentPtr) {
          winPtr->flags |= TK_GRAB_FLAG;
          if (winPtr->flags & TK_TOP_LEVEL) {
            break;
          }
      }
    }

    /*
     * Search upwards from winPtr2 until an ancestor of winPtr1 is
     * found or a top-level window is reached.
     */

    winPtr = winPtr2;
    count2 = 0;
    ancestorPtr = NULL;
    if (winPtr2 != NULL) {
      for (; winPtr != NULL; count2++, winPtr = winPtr->parentPtr) {
          if (winPtr->flags & TK_GRAB_FLAG) {
            ancestorPtr = winPtr;
            break;
          }
          if (winPtr->flags & TK_TOP_LEVEL)  {
            count2++;
            break;
          }
      }
    }

    /*
     * Search upwards from winPtr1 again, clearing the flag bits and
     * remembering how many levels up we had to go.
     */

    if (winPtr1 == NULL) {
      count1 = 0;
    } else {
      count1 = -1;
      for (i = 0, winPtr = winPtr1; winPtr != NULL;
            i++, winPtr = winPtr->parentPtr) {
          winPtr->flags &= ~TK_GRAB_FLAG;
          if (winPtr == ancestorPtr) {
            count1 = i;
          }
          if (winPtr->flags & TK_TOP_LEVEL) {
            if (count1 == -1) {
                count1 = i+1;
            }
            break;
          }
      }
    }

    *countPtr1 = count1;
    *countPtr2 = count2;
    return ancestorPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * TkPositionInTree --
 *
 *    Compute where the given window is relative to a particular
 *    subtree of the window hierarchy.
 *
 * Results:
 *
 *    Returns TK_GRAB_IN_TREE if the window is contained in the
 *    subtree.  Returns TK_GRAB_ANCESTOR if the window is an
 *    ancestor of the subtree, in the same toplevel.  Otherwise
 *    it returns TK_GRAB_EXCLUDED.
 *
 * Side effects:
 *    None.
 *
 *----------------------------------------------------------------------
 */

int
TkPositionInTree(winPtr, treePtr)
    TkWindow *winPtr;         /* Window to be checked. */
    TkWindow *treePtr;        /* Root of tree to compare against. */
{
    TkWindow *winPtr2;

    for (winPtr2 = winPtr; winPtr2 != treePtr;
         winPtr2 = winPtr2->parentPtr) {
      if (winPtr2 == NULL) {
          for (winPtr2 = treePtr; winPtr2 != NULL;
                winPtr2 = winPtr2->parentPtr) {
            if (winPtr2 == winPtr) {
                return TK_GRAB_ANCESTOR;
            }
            if (winPtr2->flags & TK_TOP_LEVEL) {
                break;
            }
          }
          return TK_GRAB_EXCLUDED;
      }
    }
    return TK_GRAB_IN_TREE;
}

/*
 *----------------------------------------------------------------------
 *
 * TkGrabState --
 *
 *    Given a window, this procedure returns a value that indicates
 *    the grab state of the application relative to the window.
 *
 * Results:
 *    The return value is one of three things:
 *        TK_GRAB_NONE -      no grab is in effect.
 *        TK_GRAB_IN_TREE -   there is a grab in effect, and winPtr
 *                      is in the grabbed subtree.
 *        TK_GRAB_ANCESTOR -  there is a grab in effect;  winPtr is
 *                      an ancestor of the grabbed window, in
 *                      the same toplevel.
 *        TK_GRAB_EXCLUDED -  there is a grab in effect; winPtr is
 *                      outside the tree of the grab and is not
 *                      an ancestor of the grabbed window in the
 *                      same toplevel.
 *
 * Side effects:
 *    None.
 *
 *----------------------------------------------------------------------
 */

int
TkGrabState(winPtr)
    TkWindow *winPtr;         /* Window for which grab information is
                         * needed. */
{
    TkWindow *grabWinPtr = winPtr->dispPtr->grabWinPtr;

    if (grabWinPtr == NULL) {
      return TK_GRAB_NONE;
    }
    if ((winPtr->mainPtr != grabWinPtr->mainPtr)
          && !(winPtr->dispPtr->grabFlags & GRAB_GLOBAL)) {
      return TK_GRAB_NONE;
    }

    return TkPositionInTree(winPtr, grabWinPtr);
}

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