[micropolis] / src / tk / tkgrab.c

/* 
 * tkGrab.c --
 *
 *      This file provides procedures that implement grabs for Tk.
 *
 * Copyright 1992 Regents of the University of California.
 * 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.  The University of California
 * makes no representations about the suitability of this
 * software for any purpose.  It is provided "as is" without
 * express or implied warranty.
 */

#ifndef lint
static char rcsid[] = "$Header: /user6/ouster/wish/RCS/tkGrab.c,v 1.18 92/08/07 09:55:31 ouster Exp $ SPRITE (Berkeley)";
#endif

#include "tkconfig.h"
#include "tkint.h"

/*
 *-------------------------------------------------------------------
 * Problems with current grab implementation (8/7/92):
 *
 * 1. In a local grab the synthesized events are always placed at the
 *    front of the event queue.  If there are several grabs and ungrabs
 *    in a row, the groups of events for the different grabs/ungrabs
 *    end up in backwards order.
 * 2. The variables serverWinPtr and pointerWinPtr are hardly used at
 *    all and should probably be eliminated.
 * 3. The fact that grabWinPtr is set at the time a grab is set or
 *    released, rather than when its events are processed, means that
 *    it can get out of sync with the event queue if there's a rapid
 *    sequence of grabs or ungrabs.  The only solution I can think of
 *    is to keep a parallel queue to the event queue to update grabWinPtr
 *    (or, synthesize an event to change the pointer?).
 *-------------------------------------------------------------------
 */

/*
 * 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_BUTTON_RELEASE          1 means that a button-release event just
 *                              occurred and we're in the middle of a sequence
 *                              of Enter and Leave events with NotifyUngrab
 *                              mode.
 */

#define GRAB_GLOBAL             1
#define GRAB_BUTTON_RELEASE     2

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

static void             ChangeEventWindow _ANSI_ARGS_((XEvent *eventPtr,
                            TkWindow *winPtr));
static void             MovePointer _ANSI_ARGS_((XEvent *eventPtr,
                            TkWindow *sourcePtr, TkWindow *destPtr));
static void             MovePointer2 _ANSI_ARGS_((TkWindow *sourcePtr,
                            TkWindow *destPtr, int mode));
\f
/*
 *----------------------------------------------------------------------
 *
 * 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. */
{
    TkWindow *winPtr = (TkWindow *) clientData;
    int length, lockScreen;
    char *window;

    if (argc > 3) {
        badArgs:
        Tcl_AppendResult(interp, "wrong # args: should be \"",
                argv[0], " ?-global? ?window?\"", (char *) NULL);
        return TCL_ERROR;
    }
    if (argc == 1) {
        if ((winPtr->dispPtr->grabWinPtr != NULL)
                && (winPtr->dispPtr->grabWinPtr->mainPtr
                == winPtr->mainPtr)) {
            interp->result = Tk_PathName(winPtr->dispPtr->grabWinPtr);
        } else {
            interp->result = "none";
        }
        return TCL_OK;
    }
    if (argc == 3) {
        length = strlen(argv[1]);
        if (strncmp(argv[1], "-off", length) == 0) {
            lockScreen = -1;
        } else {
            if ((strncmp(argv[1], "-global", length) != 0) || (length < 2)) {
                goto badArgs;
            }
            lockScreen = 1;
        }
        window = argv[2];
    } else {
        lockScreen = 0;
        window = argv[1];
    }
    if ((window[0] == '\0')
            || (strncmp(window, "none", strlen(window)) == 0)) {
        Tk_Ungrab((Tk_Window) winPtr);  
    } else {
        Tk_Window tkwin;

        tkwin = Tk_NameToWindow(interp, window, (Tk_Window) winPtr);
        if (tkwin == NULL) {
            return TCL_ERROR;
        }
        if (lockScreen < 0) {
            Tk_Ungrab(tkwin);
        } else {
            return Tk_Grab(interp, tkwin, lockScreen);
        }
    }
    return TCL_OK;
}
\f
/*
 *----------------------------------------------------------------------
 *
 * 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;
    TkWindow *winPtr = (TkWindow *) tkwin;
    TkDisplay *dispPtr = winPtr->dispPtr;
    int grabRequest, inSequence, ignoring, numEvents, i, diff;
    XEvent *events, *eventPtr;
    TkWindow *winPtr2;

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

    if (grabGlobal) {
        grabRequest = NextRequest(dispPtr->display);
        grabResult = XGrabPointer(dispPtr->display, Tk_WindowId(tkwin),
                True, ButtonPressMask|ButtonReleaseMask|ButtonMotionMask|PointerMotionMask,
                GrabModeAsync, GrabModeAsync, None, None,
                TkCurrentTime(dispPtr));
        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, TkCurrentTime(dispPtr));
        if (grabResult != 0) {
            XUngrabPointer(dispPtr->display, TkCurrentTime(dispPtr));
            goto grabError;
        }
        dispPtr->grabFlags |= GRAB_GLOBAL;
    } else {
        /*
         * The call to XUngrabPointer below is needed to release any
         * existing auto-grab due to a button press.  This is needed
         * so that local grabs behave the same as global grabs (the
         * button grab is released by the X server in a global grab).
         */

        XUngrabPointer(dispPtr->display, TkCurrentTime(dispPtr));
        grabRequest = LastKnownRequestProcessed(dispPtr->display);
        dispPtr->grabFlags &= ~GRAB_GLOBAL;

        /*
         * Since we're not telling the server about the grab, we have
         * to generate Leave and Enter events to move the pointer from
         * its current window to the grab window.
         */

        MovePointer2(dispPtr->pointerWinPtr, winPtr, NotifyGrab);
    }
    dispPtr->grabWinPtr = winPtr;

    /*
     * When a grab occurs, X generates Enter and Leave events to move
     * the pointer from its current window to the grab window, even if
     * the current window is in the grab tree.  We don't want these
     * events getting through to the application if the current window
     * is in the grab tree.  In order to eliminate the bogus events,
     * process all pending events and filter out the bogus ones.
     *
     * Also, filter out the final enter event into the grab window in
     * any case:  this event shouldn't be delivered until the mouse really
     * moves into that window.
     *
     * The code below reads in all the pending events, filters out the bad
     * ones, and then pushes back all the events that weren't filtered.
     * Another alternative would be to simply process the events
     * immediately rather than pushing them back again.  However, this
     * tends to interfere with scripts since it causes pending events
     * to be processed during the "grab" command.  The "grab" command
     * might have been invoked in the middle of some computation where
     * it's a bad idea to process new events.
     */

    XSync(dispPtr->display, False);
    numEvents = QLength(dispPtr->display);
    if (numEvents == 0) {
        return TCL_OK;
    }
    events = (XEvent *) ckalloc((unsigned) (numEvents * sizeof(XEvent)));
    for (i = 0; i < numEvents; i++) {
        XNextEvent(dispPtr->display, &events[i]);
    }
    inSequence = ignoring = 0;
    for (i = numEvents-1, eventPtr = events; i >= 0; i--, eventPtr++) {
        if (((eventPtr->type != EnterNotify)
                && (eventPtr->type != LeaveNotify))
                || (eventPtr->xcrossing.mode != NotifyGrab)) {
            continue;
        }

        /*
         * The diff caculcation below is trickier than you might think,
         * due to the fact that the event serial number is unsigned and
         * serial numbers can wrap around.
         */

        diff = eventPtr->xcrossing.serial;
        diff -= grabRequest;
        if (!inSequence && (diff >= 0)) {
            /*
             * This is the first event of the grab sequence.  See if its
             * window is in the grab tree and ignore the sequence if it is.
             */

            inSequence = 1;
            if (XFindContext(dispPtr->display, eventPtr->xcrossing.window,
                    tkWindowContext, (void *) &winPtr2) == 0) {
                for ( ; winPtr2 != NULL; winPtr2 = winPtr2->parentPtr) {
                    if (winPtr2 == dispPtr->grabWinPtr) {
                        ignoring = 1;
                        break;
                    }
                }
            }
        }
        if (ignoring) {
            eventPtr->type = 0;
        }
        if (inSequence && (eventPtr->type == EnterNotify)
                && (dispPtr->grabWinPtr->window
                == eventPtr->xcrossing.window)) {
            eventPtr->type = 0;
            break;
        }
    }
    for (i = numEvents-1, eventPtr = &events[i]; i >= 0; i--, eventPtr--) {
        if (eventPtr->type != 0) {
            XPutBackEvent(dispPtr->display, eventPtr);
        }
    }
    ckfree((char *) events);
    return TCL_OK;
}
\f
/*
 *----------------------------------------------------------------------
 *
 * Tk_Ungrab --
 *
 *      Releases a grab on the mouse pointer and keyboard.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Pointer and keyboard events will start being delivered to other
 *      windows again.
 *
 *----------------------------------------------------------------------
 */

void
Tk_Ungrab(tkwin)
    Tk_Window tkwin;                    /* Window that identifies display
                                         * for grab to be released. */
{
    TkDisplay *dispPtr = ((TkWindow *) tkwin)->dispPtr;
    int inSequence, ignoring, ungrabRequest, numEvents, i, j, diff;
    TkWindow *grabWinPtr, *winPtr;
    XEvent *events, *eventPtr, *eventPtr2;

    grabWinPtr = dispPtr->grabWinPtr;
    if (grabWinPtr == NULL) {
        return;
    }
    dispPtr->grabWinPtr = NULL;
    dispPtr->buttonWinPtr = NULL;
    if (dispPtr->grabFlags & GRAB_GLOBAL) {
        ungrabRequest = NextRequest(dispPtr->display);
        XUngrabPointer(dispPtr->display, TkCurrentTime(dispPtr));
        XUngrabKeyboard(dispPtr->display, TkCurrentTime(dispPtr));
        XSync(dispPtr->display, False);
    } else {
        ungrabRequest = LastKnownRequestProcessed(dispPtr->display);
        if ((dispPtr->ungrabWinPtr != NULL)
                && (dispPtr->ungrabWinPtr->mainPtr != grabWinPtr->mainPtr)) {

            /*
             * Don't report entries down into a window of a different
             * application, since it's already seen those entries earlier.
             */

            dispPtr->ungrabWinPtr = NULL;
        }
        MovePointer2(grabWinPtr, dispPtr->ungrabWinPtr, NotifyUngrab);
    }

    /*
     * We have to filter all the pending events in a fashion similar to
     * Tk_Grab. As with grabs, the X server generates an Enter-Leave event
     * sequence to move the pointer from the grab window back to its
     * current window.  We need to ignore this sequence if the pointer
     * is being moved to a window that's already in the grab tree.
     */

    numEvents = QLength(dispPtr->display);
    if (numEvents == 0) {
        return;
    }
    events = (XEvent *) ckalloc((unsigned) (numEvents * sizeof(XEvent)));
    for (i = 0; i < numEvents; i++) {
        XNextEvent(dispPtr->display, &events[i]);
    }
    inSequence = ignoring = 0;
    for (i = numEvents-1, eventPtr = events; i >= 0; i--, eventPtr++) {
        if (((eventPtr->type != EnterNotify)
                && (eventPtr->type != LeaveNotify))
                || (eventPtr->xcrossing.mode != NotifyUngrab)) {
            continue;
        }
        diff = eventPtr->xcrossing.serial;
        diff -= ungrabRequest;
        if (!inSequence && (diff >= 0)) {

            /*
             * This is the first event of the ungrab sequence.  Scan forward
             * looking for the final Enter event in the sequence.  Then see
             * if that event's window is in the grab tree.
             */

            inSequence = 1;
            for (j = i, eventPtr2 = eventPtr; j >= 0; j--, eventPtr2++) {
                if (eventPtr2->type == EnterNotify) {
                    if (eventPtr2->xcrossing.mode != NotifyUngrab) {
                        break;
                    }
                    if ((eventPtr2->xcrossing.detail != NotifyAncestor)
                            && (eventPtr2->xcrossing.detail != NotifyInferior)
                            && (eventPtr2->xcrossing.detail
                                    != NotifyNonlinear)) {
                        continue;
                    }
                    if (XFindContext(dispPtr->display,
                            eventPtr2->xcrossing.window,
                            tkWindowContext, (void *) &winPtr) == 0) {
                        for ( ; winPtr != NULL; winPtr = winPtr->parentPtr) {
                            if (winPtr == grabWinPtr) {
                                ignoring = 1;
                                break;
                            }
                        }
                    }
                    break;
                } else if ((eventPtr2->type != LeaveNotify)
                        || (eventPtr2->xcrossing.mode != NotifyUngrab)) {
                    break;
                }
            }
        }
        if (ignoring) {
            eventPtr->type = 0;
        }
    }
    for (i = numEvents-1, eventPtr = &events[i]; i >= 0; i--, eventPtr--) {
        if (eventPtr->type != 0) {
            XPutBackEvent(dispPtr->display, eventPtr);
        }
    }
    ckfree((char *) events);
}
\f
/*
 *----------------------------------------------------------------------
 *
 * 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.  Note:  the event may be modified by this procedure.
 *
 * Side effects:
 *      Grab state information may be updated.
 *
 *----------------------------------------------------------------------
 */

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;
    int outsideGrabTree = 0;
    int originalFlags;
    int appGrabbed = 0;                 /* Non-zero means event is being
                                         * reported to an application that is
                                         * affected by the grab. */
#define ALL_BUTTONS \
        (Button1Mask|Button2Mask|Button3Mask|Button4Mask|Button5Mask)
    static unsigned int state[] = {
        Button1Mask, Button2Mask, Button3Mask, Button4Mask, Button5Mask
    };

    /*
     * Don't do any filtering on events generated by the event-sharing code.
     */

    if (eventPtr == tkShareEventPtr) {
        return 1;
    }

    /*
     * If a grab is in effect, see if the event is being reported to
     * a window in the grab tree.  Also see if the event is being reported
     * to an application that is affected by the grab.
     */

    if (dispPtr->grabWinPtr != NULL) {
        if ((winPtr->mainPtr == dispPtr->grabWinPtr->mainPtr)
                || (dispPtr->grabFlags & GRAB_GLOBAL)) {
            appGrabbed = 1;
        }
        for (winPtr2 = winPtr; winPtr2 != dispPtr->grabWinPtr;
                winPtr2 = winPtr2->parentPtr) {
            if (winPtr2 == NULL) {
                outsideGrabTree = 1;
                break;
            }
        }
    }

    originalFlags = dispPtr->grabFlags;
    dispPtr->grabFlags &= ~GRAB_BUTTON_RELEASE;
    if ((eventPtr->type == EnterNotify) || (eventPtr->type == LeaveNotify)) {
        if ((eventPtr->type == EnterNotify)
                && (eventPtr->xcrossing.detail != NotifyVirtual)
                && (eventPtr->xcrossing.detail != NotifyNonlinearVirtual)) {
            if ((dispPtr->grabWinPtr == NULL)
                    || (dispPtr->grabWinPtr->mainPtr == winPtr->mainPtr)) {
                dispPtr->ungrabWinPtr = winPtr;
            }
            dispPtr->serverWinPtr = winPtr;
        } else {
            dispPtr->serverWinPtr = NULL;
        }
        if (dispPtr->grabWinPtr != NULL) {
            if (eventPtr->xcrossing.mode == NotifyNormal) {
                /*
                 * When a grab is active, X continues to report enter and
                 * leave events for windows outside the tree of the grab
                 * window.  Detect these events and ignore them.
                 */

                if (outsideGrabTree && appGrabbed) {
                    return 0;
                }
    
                /*
                 * 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;
                }
            } else if (eventPtr->xcrossing.mode == NotifyUngrab) {
                /*
                 * Keep the GRAB_BUTTON_RELEASE flag on if it used to be on.
                 */

                dispPtr->grabFlags = originalFlags;
                if (outsideGrabTree && appGrabbed
                        && (dispPtr->grabFlags & GRAB_BUTTON_RELEASE)) {
                    /*
                     * The only way we get here is if a button was pressed,
                     * then moved to a different window and released.  Enter
                     * and leave events were deferred while the button was
                     * down, but now we're getting them to move the pointer
                     * back to the right window, and this particular event
                     * is for a window outside the grab tree.  Ignore it.
                     */
    
                    return 0;
                }
            }
        }

        /*
         * Keep track of the window containing the mouse, in order to
         * detect various bogus event sequences.
         */

        dispPtr->pointerWinPtr = dispPtr->serverWinPtr;
        return 1;
    }
    if ((dispPtr->grabWinPtr == NULL) || !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) {
            XEvent newEvent;

            newEvent = *eventPtr;
            ChangeEventWindow(&newEvent, winPtr2);
            XPutBackEvent(winPtr2->display, &newEvent);
            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.
     */

    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) {
                    XEvent newEvent;

                    newEvent = *eventPtr;
                    ChangeEventWindow(&newEvent, dispPtr->grabWinPtr);
                    XPutBackEvent(dispPtr->display, &newEvent);
                    return 0;                                   /* Note 2. */
                }
                dispPtr->buttonWinPtr = winPtr;
                return 1;
            }
        } else {
            if ((eventPtr->xbutton.state & ALL_BUTTONS)
                    == state[eventPtr->xbutton.button - Button1]) {
                if ((dispPtr->buttonWinPtr != winPtr)
                        && (dispPtr->buttonWinPtr != NULL)) {
                    XEvent newEvent;                            /* Note 4. */

                    /*
                     * If the button release is made with pointer outside
                     * all applications, X reports it relative to the grab
                     * window.   Change the current window to NULL to
                     * reflect that the pointer's outside everything.  Do
                     * the same if the pointer's in a window that's not
                     * part of the grab tree.
                     */

                    if (outsideGrabTree || (dispPtr->serverWinPtr == NULL)) {
                        winPtr = NULL;
                    }
                    newEvent = *eventPtr;
                    newEvent.xcrossing.mode = NotifyUngrab;
                    newEvent.xcrossing.focus = False;
                    newEvent.xcrossing.state =
                            eventPtr->xbutton.state & ~ALL_BUTTONS;
                    MovePointer(&newEvent, dispPtr->buttonWinPtr, winPtr);
                }
                dispPtr->buttonWinPtr = NULL;
                dispPtr->grabFlags |= GRAB_BUTTON_RELEASE;
            }
        }
        if (winPtr2 != winPtr) {
            XEvent newEvent;

            newEvent = *eventPtr;
            ChangeEventWindow(&newEvent, winPtr2);
            XPutBackEvent(dispPtr->display, &newEvent);
            return 0;                                           /* Note 3. */
        }
    }

    return 1;
}
\f
/*
 *----------------------------------------------------------------------
 *
 * ChangeEventWindow --
 *
 *      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.
 *
 *----------------------------------------------------------------------
 */

static void
ChangeEventWindow(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.width + 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;
    }
}
\f
/*
 *----------------------------------------------------------------------
 *
 * MovePointer --
 *
 *      This procedure synthesizes EnterNotify and LeaveNotify events
 *      to correctly transfer the pointer from one window to another.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Synthesized events may be pushed back onto the event queue.
 *      The event pointed to by eventPtr is modified.
 *
 *----------------------------------------------------------------------
 */

static void
MovePointer(eventPtr, sourcePtr, destPtr)
    XEvent *eventPtr;           /* A template X event.  Must have all fields
                                 * properly set for EnterNotify and LeaveNotify
                                 * events except window, subwindow, x, y,
                                 * detail, and same_screen.  (x_root and y_root
                                 * must be valid, even though x and y needn't
                                 * be valid). */
    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). */
{
    TkDisplay *dispPtr;
    register TkWindow *ancestorPtr;     /* Lowest ancestor shared between
                                         * sourcePtr and destPtr, or
                                         * sourcePtr's top-level window if no
                                         * shared ancestor. */
    register TkWindow *winPtr;
    int upLevels, downLevels, i, j;

    /*
     * 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 code below separates these four cases and decides how many levels
     * up and down events have to be generated for.
     */

    if (sourcePtr == destPtr) {
        return;
    }

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

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

    /*
     * Search upwards from sourcePtr until an ancestor of destPtr is
     * found or a top-level window is reached.  Remember if we pass out
     * of the grab tree along the way, since this means we'll have to
     * skip some of the events that would otherwise be generated.
     */

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

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

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

    /*
     * Generate enter/leave events and push them back onto the event
     * queue.  This has to be done backwards, since the last event
     * pushed will be the first one processed.
     */

#define PUSH_EVENT(w, t, d)                     \
    if (w->window != None) {                    \
        eventPtr->type = t;                     \
        eventPtr->xcrossing.detail = d;         \
        ChangeEventWindow(eventPtr, w);         \
        XPutBackEvent(w->display, eventPtr);    \
    }

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

        if (destPtr != NULL) {
            PUSH_EVENT(destPtr, EnterNotify, NotifyInferior);
        }
        for (i = upLevels-1; i > 0; i--) {
            for (winPtr = sourcePtr, j = 0; j < i;
                    winPtr = winPtr->parentPtr, j++) {
                if (winPtr == dispPtr->grabWinPtr) {
                    goto nextIteration;
                }
            }
            PUSH_EVENT(winPtr, LeaveNotify, NotifyVirtual);
            nextIteration: continue;
        }
        PUSH_EVENT(sourcePtr, LeaveNotify, NotifyAncestor);
    } else if (upLevels == 0) {

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

        if (destPtr != NULL) {
            PUSH_EVENT(destPtr, EnterNotify, NotifyAncestor);
        }
        for (winPtr = destPtr->parentPtr, i = downLevels-1; i > 0;
                winPtr = winPtr->parentPtr, i--) {
            PUSH_EVENT(winPtr, EnterNotify, NotifyVirtual);
        }
        if (sourcePtr != NULL) {
            PUSH_EVENT(sourcePtr, LeaveNotify, NotifyInferior);
        }
    } else {

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

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

static void
MovePointer2(sourcePtr, destPtr, mode)
    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. */
{
    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 = False;
    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;
    MovePointer(&event, sourcePtr, destPtr);
}
\f
/*
 *----------------------------------------------------------------------
 *
 * 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->grabWinPtr == winPtr) {
        dispPtr->grabWinPtr = NULL;
        if (!(dispPtr->grabFlags & GRAB_GLOBAL)) {
            /*
             * Must generate enter/leave events to move back to the window
             * that contains the mouse pointer.  We needn't filter events
             * here like we do in Tk_Ungrab because there are no children
             * of the grab window left in existence.
             */

            movePointerBack:
            if ((dispPtr->ungrabWinPtr != NULL)
                    && (dispPtr->ungrabWinPtr->mainPtr != winPtr->mainPtr)) {
                dispPtr->ungrabWinPtr = NULL;
            }
            MovePointer2(winPtr, dispPtr->ungrabWinPtr, NotifyUngrab);
        }
    } else if (dispPtr->buttonWinPtr == winPtr) {
        /*
         * The window in which a button was pressed was deleted.  Simulate
         * dropping the button auto-grab by generating Enter and Leave
         * events to move the pointer back to the window it's really on
         * top of.
         */

        dispPtr->buttonWinPtr = NULL;
        goto movePointerBack;
    }
    if (dispPtr->ungrabWinPtr == winPtr) {
        dispPtr->ungrabWinPtr = NULL;
    }
    if (dispPtr->pointerWinPtr == winPtr) {
        dispPtr->pointerWinPtr = NULL;
    }
    if (dispPtr->serverWinPtr == winPtr) {
        dispPtr->serverWinPtr = NULL;
    }
}