Index: macosx/tkMacOSXMouseEvent.c
==================================================================
--- macosx/tkMacOSXMouseEvent.c
+++ macosx/tkMacOSXMouseEvent.c
@@ -51,10 +51,11 @@
 {
     NSWindow *eventWindow = [theEvent window];
     NSEventType eventType = [theEvent type];
     TkWindow *winPtr, *grabWinPtr;
     Tk_Window tkwin;
+    NSPoint local, global;
 #if 0
     NSTrackingArea *trackingArea = nil;
     NSInteger eventNumber, clickCount, buttonNumber;
 #endif
 
@@ -81,66 +82,59 @@
 	break;
     default: /* Unrecognized mouse event. */
 	return theEvent;
     }
 
-    /*
-     * Remember the window in case we need it next time.
-     */
-
-    if (eventWindow && eventWindow != _windowWithMouse) {
-	if (_windowWithMouse) {
-	    [_windowWithMouse release];
-	}
-	_windowWithMouse = eventWindow;
-	[_windowWithMouse retain];
-    }
-
     /*
      * Compute the mouse position in Tk screen coordinates (global) and in the
-     * Tk coordinates of its containing Tk Window.
+     * Tk coordinates of its containing Tk Window (local). If a grab is in effect,
+     * the local coordinates should be relative to the grab window.
      */
 
-    NSPoint global, local = [theEvent locationInWindow];
-
-    /*
-     * If the event has no NSWindow, try using the cached NSWindow from the
-     * last mouse event.
-     */
-
-    if (eventWindow == NULL) {
-	eventWindow = _windowWithMouse;
-    }
     if (eventWindow) {
-	/*
-	 * Set the local mouse position to its NSWindow flipped coordinates,
-	 * with the origin at top left, and the global mouse position to the
-	 * flipped screen coordinates.
-	 */
-
+	local = [theEvent locationInWindow];
 	global = [eventWindow tkConvertPointToScreen: local];
+	tkwin = TkMacOSXGetCapture();
+	if (tkwin) {
+	    winPtr = (TkWindow *) tkwin;
+	    eventWindow = TkMacOSXDrawableWindow(winPtr->window);
+	    if (eventWindow) {
+		local = [eventWindow tkConvertPointFromScreen: global];
+	    } else {
+		return theEvent;
+	    }
+	}
 	local.y = [eventWindow frame].size.height - local.y;
 	global.y = tkMacOSXZeroScreenHeight - global.y;
     } else {
-	/*
-	 * As a last resort, with no NSWindow to work with, set both local and
-	 * global to the screen coordinates.
-	 */
-
-	local.y = tkMacOSXZeroScreenHeight - local.y;
-	global = local;
-    }
-
-    /*
-     * Find the toplevel which corresponds to the event NSWindow.
-     */
-
-    winPtr = TkMacOSXGetTkWindow(eventWindow);
-    if (winPtr == NULL) {
-	tkwin = TkMacOSXGetCapture();
-	winPtr = (TkWindow *) tkwin;
-    } else {
+	
+	/*
+	 * If the event has no NSWindow, the location is in screen coordinates.
+	 */
+
+	global = [theEvent locationInWindow];
+	tkwin = TkMacOSXGetCapture();
+	if (tkwin) {
+	    winPtr = (TkWindow *) tkwin;
+	    eventWindow = TkMacOSXDrawableWindow(winPtr->window);
+	} else {
+	    eventWindow = [NSApp mainWindow];
+	}
+	if (!eventWindow) {
+	    return theEvent;
+	}
+	local = [eventWindow tkConvertPointFromScreen: global];
+	local.y = [eventWindow frame].size.height - local.y;
+	global.y = tkMacOSXZeroScreenHeight - global.y;
+    }
+
+    /*
+     * Make sure tkwin is the toplevel which should receive the event.
+     */
+
+    if (!tkwin) {
+	winPtr = TkMacOSXGetTkWindow(eventWindow);
 	tkwin = (Tk_Window) winPtr;
     }
     if (!tkwin) {
 #ifdef TK_MAC_DEBUG_EVENTS
 	TkMacOSXDbgMsg("tkwin == NULL");

Index: macosx/tkMacOSXPrivate.h
==================================================================
--- macosx/tkMacOSXPrivate.h
+++ macosx/tkMacOSXPrivate.h
@@ -261,11 +261,10 @@
     Tcl_Interp *_eventInterp;
     NSMenu *_servicesMenu;
     TKMenu *_defaultMainMenu, *_defaultApplicationMenu;
     NSArray *_defaultApplicationMenuItems, *_defaultWindowsMenuItems;
     NSArray *_defaultHelpMenuItems;
-    NSWindow *_windowWithMouse;
     NSAutoreleasePool *_mainPool;
 #ifdef __i386__
     /* The Objective C runtime used on i386 requires this. */
     int _poolLock;
     int _macMinorVersion;

Index: macosx/tkMacOSXWindowEvent.c
==================================================================
--- macosx/tkMacOSXWindowEvent.c
+++ macosx/tkMacOSXWindowEvent.c
@@ -196,14 +196,10 @@
 #endif
     TkWindow *winPtr = TkMacOSXGetTkWindow(w);
 
     if (winPtr) {
 	TkGenWMDestroyEvent((Tk_Window) winPtr);
-	if (_windowWithMouse == w) {
-	    _windowWithMouse = nil;
-	    [w release];
-	}
     }
 
     /*
      * If necessary, TkGenWMDestroyEvent() handles [close]ing the window, so
      * can always return NO from -windowShouldClose: for a Tk window.

Index: macosx/tkMacOSXWm.c
==================================================================
--- macosx/tkMacOSXWm.c
+++ macosx/tkMacOSXWm.c
@@ -338,22 +338,16 @@
     return [self convertScreenToBase:point];
 }
 #else
 - (NSPoint) tkConvertPointToScreen: (NSPoint) point
 {
-    NSRect pointrect;
-    pointrect.origin = point;
-    pointrect.size.width = 0;
-    pointrect.size.height = 0;
+    NSRect pointrect = {point, {0,0}};
     return [self convertRectToScreen:pointrect].origin;
 }
 - (NSPoint) tkConvertPointFromScreen: (NSPoint)point
 {
-    NSRect pointrect;
-    pointrect.origin = point;
-    pointrect.size.width = 0;
-    pointrect.size.height = 0;
+    NSRect pointrect = {point, {0,0}};
     return [self convertRectFromScreen:pointrect].origin;
 }
 #endif
 
 @end