Bug 610391 - Create the widget for drop-down comboboxes lazily, and tear it down when the drop-down is closed; r=roc

layout/base/nsCSSFrameConstructor.cpp

@@ -3216,19 +3216,6 @@ nsCSSFrameConstructor::InitializeSelectFrame(nsFrameConstructorState& aState,
   }
       
   nsHTMLContainerFrame::CreateViewForFrame(scrollFrame, aBuildCombobox);
-  if (aBuildCombobox) {
-    // Give the drop-down list a popup widget
-    nsIView* view = scrollFrame->GetView();
-    NS_ASSERTION(view, "We asked for a view but didn't get one");
-    if (view) {
-      view->GetViewManager()->SetViewFloating(view, PR_TRUE);
-
-      nsWidgetInitData widgetData;
-      widgetData.mWindowType  = eWindowType_popup;
-      widgetData.mBorderStyle = eBorderStyle_default;
-      view->CreateWidgetForPopup(&widgetData);
-    }
-  }
 
   BuildScrollFrame(aState, aContent, aStyleContext, scrolledFrame,
                    geometricParent, scrollFrame);

layout/forms/nsComboboxControlFrame.cpp

@@ -387,6 +387,21 @@ nsComboboxControlFrame::ShowList(PRBool aShowList)
   nsCOMPtr<nsIPresShell> shell = PresContext()->GetPresShell();
 
   nsWeakFrame weakFrame(this);
+
+  if (aShowList) {
+    nsIView* view = mDropdownFrame->GetView();
+    NS_ASSERTION(!view->HasWidget(),
+                 "We shoudldn't have a widget before we need to display the popup");
+
+    // Create the widget for the drop-down list
+    view->GetViewManager()->SetViewFloating(view, PR_TRUE);
+
+    nsWidgetInitData widgetData;
+    widgetData.mWindowType  = eWindowType_popup;
+    widgetData.mBorderStyle = eBorderStyle_default;
+    view->CreateWidgetForPopup(&widgetData);
+  }
+
   ShowPopup(aShowList);  // might destroy us
   if (!weakFrame.IsAlive()) {
     return PR_FALSE;
@@ -412,8 +427,13 @@ nsComboboxControlFrame::ShowList(PRBool aShowList)
     NS_ASSERTION(view, "nsComboboxControlFrame view is null");
     if (view) {
       nsIWidget* widget = view->GetWidget();
-      if (widget)
+      if (widget) {
         widget->CaptureRollupEvents(this, nsnull, mDroppedDown, mDroppedDown);
+
+        if (!aShowList) {
+          view->DestroyWidget();
+        }
+      }
     }
   }
 

view/public/nsIView.h

@@ -62,8 +62,8 @@ enum nsViewVisibility {
 };
 
 #define NS_IVIEW_IID    \
-  { 0xd0c2cf54, 0xb527, 0x4d8e, \
-    { 0xba, 0x87, 0x39, 0x03, 0xa7, 0xc4, 0x13, 0xe1 } }
+  { 0x63052d96, 0x2a4b, 0x434f, \
+    { 0xb4, 0xd3, 0x61, 0x41, 0x83, 0x24, 0x00, 0x76 } }
 
 // Public view flags are defined in this file
 #define NS_VIEW_FLAGS_PUBLIC              0x00FF
@@ -313,6 +313,13 @@ public:
                                 PRBool aEnableDragDrop = PR_TRUE,
                                 PRBool aResetVisibility = PR_TRUE);
 
+  /**
+   * Destroys the associated widget for this view.  If this method is
+   * not called explicitly, the widget when be destroyed when its
+   * view gets destroyed.
+   */
+  void DestroyWidget();
+
   /**
    * Attach/detach a top level widget from this view. When attached, the view
    * updates the widget's device context and allows the view to begin receiving

view/src/nsView.cpp

@@ -268,6 +268,17 @@ nsView::~nsView()
   }
 
   // Destroy and release the widget
+  DestroyWidget();
+
+  delete mDirtyRegion;
+
+  if (mDeletionObserver) {
+    mDeletionObserver->Clear();
+  }
+}
+
+void nsView::DestroyWidget()
+{
   if (mWindow)
   {
     // Release memory for the view wrapper
@@ -291,11 +302,6 @@ nsView::~nsView()
 
     NS_RELEASE(mWindow);
   }
-  delete mDirtyRegion;
-
-  if (mDeletionObserver) {
-    mDeletionObserver->Clear();
-  }
 }
 
 nsresult nsView::QueryInterface(const nsIID& aIID, void** aInstancePtr)
@@ -685,6 +691,11 @@ nsresult nsIView::CreateWidgetForPopup(nsWidgetInitData *aWidgetInitData,
                                       aEnableDragDrop, aResetVisibility);
 }
 
+void nsIView::DestroyWidget()
+{
+  Impl()->DestroyWidget();
+}
+
 struct DefaultWidgetInitData : public nsWidgetInitData {
   DefaultWidgetInitData() : nsWidgetInitData()
   {

view/src/nsView.h

@@ -134,6 +134,9 @@ public:
                                 PRBool aEnableDragDrop,
                                 PRBool aResetVisibility);
 
+  // See nsIView::DestroyWidget
+  void DestroyWidget();
+
   // NOT in nsIView, so only available in view module
   // These are also present in nsIView, but these versions return nsView and nsViewManager
   // instead of nsIView and nsIViewManager.