Bug 596222 - Crash [@ mozilla::widget::WindowHook::Lookup] on shutdown with MaxTo enabled. r=robarnold

widget/src/windows/TaskbarPreview.cpp

@@ -282,6 +282,17 @@ TaskbarPreview::Disable() {
   return NS_OK;
 }
 
+PRBool
+TaskbarPreview::IsWindowAvailable() const {
+  if (mWnd) {
+    nsWindow* win = nsWindow::GetNSWindowPtr(mWnd);
+    if(win && !win->HasDestroyStarted()) {
+      return PR_TRUE;
+    }
+  }
+  return PR_FALSE;
+}
+
 void
 TaskbarPreview::DetachFromNSWindow() {
   WindowHook &hook = GetWindowHook();

widget/src/windows/TaskbarPreview.h

@@ -76,6 +76,9 @@ protected:
   // Detaches this preview from the nsWindow instance it's tied to
   virtual void DetachFromNSWindow();
 
+  // Determines if the window is available and a destroy has not yet started
+  PRBool IsWindowAvailable() const;
+
   // Marks this preview as being active
   virtual nsresult ShowActive(PRBool active) = 0;
   // Gets a reference to the window used to handle the preview messages

widget/src/windows/TaskbarTabPreview.cpp

@@ -76,8 +76,11 @@ TaskbarTabPreview::~TaskbarTabPreview() {
 
   NS_ASSERTION(!mProxyWindow, "Taskbar proxy window was not destroyed!");
 
-  if (mWnd)
+  if (IsWindowAvailable()) {
     DetachFromNSWindow();
+  } else {
+    mWnd = NULL;
+  }
 }
 
 nsresult

widget/src/windows/TaskbarWindowPreview.cpp

@@ -101,8 +101,11 @@ TaskbarWindowPreview::TaskbarWindowPreview(ITaskbarList4 *aTaskbar, nsITaskbarPr
 }
 
 TaskbarWindowPreview::~TaskbarWindowPreview() {
-  if (mWnd)
+  if (IsWindowAvailable()) {
     DetachFromNSWindow();
+  } else {
+    mWnd = NULL;
+  }
 }
 
 nsresult

widget/src/xpwidgets/nsBaseWidget.h

@@ -219,6 +219,11 @@ public:
   };
   friend class AutoUseBasicLayerManager;
 
+  PRBool HasDestroyStarted() const 
+  {
+    return mOnDestroyCalled;
+  }
+
   PRBool                  Destroyed() { return mOnDestroyCalled; }
 
 protected: