when a Layer or WinBorder is deleted, the RootLayer gets a chance to set some important pointers it keeps arround to NULL. It is not unlikely that this improves stability a bit.

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@13534 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/servers/app/RootLayer.cpp

@@ -1356,7 +1356,7 @@ fprintf(stderr, "mouse position changed in B_MOUSE_UP (%.1f, %.1f) from last B_M
 					winBorderUnder = (WinBorder*)fEventMaskLayer;
 				}
 			} else {
-				if (fLastMouseMoved != target) {
+				if (fLastMouseMoved && fLastMouseMoved != target) {
 					fViewAction = B_EXITED_VIEW;
 					if (fLastMouseMoved->fOwner) {
 						if (fLastMouseMoved != fLastMouseMoved->fOwner->fTopLayer) {
@@ -1831,6 +1831,21 @@ RootLayer::SetEventMaskLayer(Layer *lay, uint32 mask, uint32 options)
 	return returnValue;
 }
 
+// LayerRemoved
+void
+RootLayer::LayerRemoved(Layer* layer)
+{
+	if (layer == fEventMaskLayer) {
+		fEventMaskLayer = NULL;
+	}
+	if (layer == fLastMouseMoved) {
+		fLastMouseMoved = NULL;
+	}
+	if (layer == fMouseTargetWinBorder) {
+		fMouseTargetWinBorder = NULL;
+	}
+}
+
 void
 RootLayer::SetDragMessage(BMessage* msg)
 {

src/servers/app/RootLayer.h

@@ -123,6 +123,8 @@ public:
 
 			bool				SetEventMaskLayer(Layer *lay, uint32 mask, uint32 options);
 
+			void				LayerRemoved(Layer* layer);
+
 	static	int32				WorkingThread(void *data);
 
 			CursorManager&		GetCursorManager() { return fCursorManager; }

src/servers/app/ServerWindow.cpp

@@ -103,6 +103,13 @@ ServerWindow::~ServerWindow()
 	if (!fWinBorder->IsOffscreenWindow())
 		gDesktop->RemoveWinBorder(fWinBorder);
 
+	// just to be safe
+	RootLayer* rootLayer = fWinBorder->GetRootLayer();
+	if (rootLayer && rootLayer->Lock()) {
+		rootLayer->LayerRemoved(fWinBorder);
+		rootLayer->Unlock();
+	}
+
 	delete fWinBorder;
 
 	free(const_cast<char *>(fTitle));
@@ -639,10 +646,16 @@ ServerWindow::_DispatchMessage(int32 code, BPrivate::LinkReceiver &link)
 			fCurrentLayer->RemoveSelf();
 			fCurrentLayer->PruneTree();
 
-			if (invalidRegion && myRootLayer) {
+			if (myRootLayer) {
+
+				myRootLayer->LayerRemoved(fCurrentLayer);
+
+				// trigger update
+				if (invalidRegion) {
 					myRootLayer->GoInvalidate(parent, *invalidRegion);
 					delete invalidRegion;
 				}
+			}
 			
 			#ifdef DEBUG_SERVERWINDOW
 			parent->PrintTree();
@@ -650,6 +663,7 @@ ServerWindow::_DispatchMessage(int32 code, BPrivate::LinkReceiver &link)
 			STRACE(("DONE: ServerWindow %s: Message AS_DELETE_LAYER: Parent: %s Layer: %s\n", fTitle, parent->Name(), fCurrentLayer->Name()));
 
 			delete fCurrentLayer;
+// TODO: It is necessary to do this, but I find it very obscure.
 			fCurrentLayer = parent;
 			break;
 		}