Bug 232951. Make scrolling of scrolling-views-without-widgets work properly even when there are child widgets. r+sr=dbaron

view/src/nsScrollPortView.cpp

@@ -378,32 +378,29 @@ NS_IMETHODIMP nsScrollPortView::GetScrollbarVisibility(PRBool *aVerticalVisible,
   return NS_OK;
 }
 
-void nsScrollPortView::AdjustChildWidgets(nsScrollPortView *aScrolling, nsView *aView, nscoord aDx, nscoord aDy, float scale)
+static void AdjustChildWidgets(nsView *aView,
+  nsPoint aWidgetToParentViewOrigin, float aScale, PRBool aInvalidate)
 {
-  NS_ASSERTION(aScrolling != aView, "We should only be scrolling children of aScrolling");
-
-  nsPoint pt = aView->GetPosition();
-
-  aDx += pt.x;
-  aDy += pt.y;
-
-  for (nsView* kid = aView->GetFirstChild(); kid; kid = kid->GetNextSibling())
-  {
-    nsIWidget *win = kid->GetWidget();
-    if (win)
-    {
-#if 0
-      win->BeginResizingChildren();
-#endif
-      nsRect  bounds = kid->GetBounds();
-
-      win->Move(NSTwipsToIntPixels((bounds.x + aDx), scale), NSTwipsToIntPixels((bounds.y + aDy), scale));
+  if (aView->HasWidget()) {
+    nsRect bounds = aView->GetBounds();
+    nsPoint widgetOrigin = aWidgetToParentViewOrigin
+      + nsPoint(bounds.x, bounds.y);
+    nsIWidget* widget = aView->GetWidget();
+    widget->Move(NSTwipsToIntPixels(widgetOrigin.x, aScale),
+                 NSTwipsToIntPixels(widgetOrigin.y, aScale));
+    if (aInvalidate) {
+      widget->Invalidate(PR_FALSE);
     }
-
+  } else {
     // Don't recurse if the view has a widget, because we adjusted the view's
     // widget position, and its child widgets are relative to its positon
-    if (!win)
-      AdjustChildWidgets(aScrolling, kid, aDx, aDy, scale);
+    nsPoint widgetToViewOrigin = aWidgetToParentViewOrigin
+      + aView->GetPosition();
+
+    for (nsView* kid = aView->GetFirstChild(); kid; kid = kid->GetNextSibling())
+    {
+      AdjustChildWidgets(kid, widgetToViewOrigin, aScale, aInvalidate);
+    }
   }
 }
 
@@ -525,12 +522,27 @@ void nsScrollPortView::Scroll(nsView *aScrolledView, PRInt32 aDx, PRInt32 aDy, f
  
     if (!scrollWidget)
     {
-      // if we don't have a scroll widget then we must just update.
+      nsPoint offsetToWidget;
+      GetNearestWidget(&offsetToWidget);
+      // We're moving the child widgets because we are scrolling. But
+      // the child widgets may stick outside our bounds, so their area
+      // may include area that's not supposed to be scrolled. We need
+      // to invalidate to ensure that any such area is properly
+      // repainted back to the right rendering.
+      AdjustChildWidgets(aScrolledView, offsetToWidget, scale, PR_TRUE);
+      // If we don't have a scroll widget then we must just update.
+      // We should call this after fixing up the widget positions to be
+      // consistent with the view hierarchy.
       mViewManager->UpdateView(this, 0);
     } else if (CannotBitBlt(aScrolledView)) {
-      // we can't blit for some reason just update the view and adjust any heavy weight widgets
+      // We can't blit for some reason.
+      // Just update the view and adjust widgets
+      // Recall that our widget's origin is at our bounds' top-left
+      AdjustChildWidgets(aScrolledView,
+                         GetPosition() - GetBounds().TopLeft(), scale, PR_FALSE);
+      // We should call this after fixing up the widget positions to be
+      // consistent with the view hierarchy.
       mViewManager->UpdateView(this, 0);
-      AdjustChildWidgets(this, aScrolledView, 0, 0, scale);
     } else { // if we can blit and have a scrollwidget then scroll.
       // Scroll the contents of the widget by the specfied amount, and scroll
       // the child widgets

view/src/nsScrollPortView.h

@@ -112,7 +112,6 @@ protected:
   virtual ~nsScrollPortView();
 
   //private
-  void AdjustChildWidgets(nsScrollPortView *aScrolling, nsView *aView, nscoord aDx, nscoord aDy, float aScale);
   void Scroll(nsView *aScrolledView, PRInt32 aDx, PRInt32 aDy, float scale, PRUint32 aUpdateFlags);
   PRBool CannotBitBlt(nsView* aScrolledView);