Bug 722012 - Fixes crash on Gtk widget destruction when using OMTC on linux. r=karlt

--HG--
extra : rebase_source : 5562c7e466bd54fecd69e8a9b4c469e24493542f

widget/gtk2/nsWindow.cpp

@@ -624,6 +624,13 @@ nsWindow::Destroy(void)
     }
     mLayerManager = nsnull;
 
+    // It is safe to call DestroyeCompositor several times (here and 
+    // in the parent class) since it will take effect only once.
+    // The reason we call it here is because on gtk platforms we need 
+    // to destroy the compositor before we destroy the gdk window (which
+    // destroys the the gl context attached to it).
+    DestroyCompositor();
+
     ClearCachedResources();
 
     g_signal_handlers_disconnect_by_func(gtk_settings_get_default(),

widget/xpwidgets/nsBaseWidget.cpp

@@ -110,7 +110,7 @@ nsBaseWidget::nsBaseWidget()
 }
 
 
-static void DestroyCompositor(CompositorParent* aCompositorParent,
+static void DeferredDestroyCompositor(CompositorParent* aCompositorParent,
                               CompositorChild* aCompositorChild,
                               Thread* aCompositorThread)
 {
@@ -120,6 +120,27 @@ static void DestroyCompositor(CompositorParent* aCompositorParent,
     aCompositorChild->Release();
 }
 
+void nsBaseWidget::DestroyCompositor() 
+{
+  if (mCompositorChild) {
+    mCompositorChild->SendWillStop();
+
+    // The call just made to SendWillStop can result in IPC from the
+    // CompositorParent to the CompositorChild (e.g. caused by the destruction
+    // of shared memory). We need to ensure this gets processed by the
+    // CompositorChild before it gets destroyed. It suffices to ensure that
+    // events already in the MessageLoop get processed before the
+    // CompositorChild is destroyed, so we add a task to the MessageLoop to
+    // handle compositor desctruction.
+    MessageLoop::current()->PostTask(FROM_HERE,
+               NewRunnableFunction(DeferredDestroyCompositor, mCompositorParent,
+                                   mCompositorChild, mCompositorThread));
+    // The DestroyCompositor task we just added to the MessageLoop will handle
+    // releasing mCompositorParent and mCompositorChild.
+    mCompositorParent.forget();
+    mCompositorChild.forget();
+  }
+}
 
 //-------------------------------------------------------------------------
 //
@@ -138,25 +159,7 @@ nsBaseWidget::~nsBaseWidget()
     mLayerManager = nsnull;
   }
 
-  if (mCompositorChild) {
-    mCompositorChild->SendWillStop();
-
-    // The call just made to SendWillStop can result in IPC from the
-    // CompositorParent to the CompositorChild (e.g. caused by the destruction
-    // of shared memory). We need to ensure this gets processed by the
-    // CompositorChild before it gets destroyed. It suffices to ensure that
-    // events already in the MessageLoop get processed before the
-    // CompositorChild is destroyed, so we add a task to the MessageLoop to
-    // handle compositor desctruction.
-    MessageLoop::current()->
-      PostTask(FROM_HERE,
-               NewRunnableFunction(DestroyCompositor, mCompositorParent,
-                                   mCompositorChild, mCompositorThread));
-    // The DestroyCompositor task we just added to the MessageLoop will handle
-    // releasing mCompositorParent and mCompositorChild.
-    mCompositorParent.forget();
-    mCompositorChild.forget();
-  }
+  DestroyCompositor();
 
 #ifdef NOISY_WIDGET_LEAKS
   gNumWidgets--;

widget/xpwidgets/nsBaseWidget.h

@@ -266,6 +266,17 @@ protected:
   BasicLayerManager* CreateBasicLayerManager();
 
 protected:
+  /**
+   * Starts the OMTC compositor destruction sequence.
+   *
+   * When this function returns, the compositor should not be 
+   * able to access the opengl context anymore.
+   * It is safe to call it several times if platform implementations
+   * require the compositor to be destroyed before ~nsBaseWidget is
+   * reached (This is the case with gtk2 for instance).
+   */
+  void DestroyCompositor();
+
   void*             mClientData;
   ViewWrapper*      mViewWrapperPtr;
   EVENT_CALLBACK    mEventCallback;