Bug 388359: Menu items are highlighted as mouse pointer moves below menu. Fix makes GetEventCoordinatesRelativeTo work across window roots. r+sr=roc.

layout/base/nsLayoutUtils.cpp

@@ -655,20 +655,47 @@ nsLayoutUtils::GetEventCoordinatesForNearestView(nsEvent* aEvent,
                                GUIEvent->refPoint, frameView);
 }
 
+static nsPoint GetWidgetOffset(nsIWidget* aWidget, nsIWidget*& aRootWidget) {
+  nsPoint offset(0, 0);
+  nsIWidget* parent = aWidget->GetParent();
+  while (parent) {
+    nsRect bounds;
+    aWidget->GetBounds(bounds);
+    offset += bounds.TopLeft();
+    aWidget = parent;
+    parent = aWidget->GetParent();
+  }
+  aRootWidget = aWidget;
+  return offset;
+}
+
 nsPoint
 nsLayoutUtils::TranslateWidgetToView(nsPresContext* aPresContext, 
                                      nsIWidget* aWidget, nsIntPoint aPt,
                                      nsIView* aView)
 {
-  nsIView* baseView = nsIView::GetViewFor(aWidget);
-  if (!baseView)
-    return nsPoint(NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE);
-  nsPoint viewToWidget;
-  nsIWidget* wid = baseView->GetNearestWidget(&viewToWidget);
-  NS_ASSERTION(aWidget == wid, "Clashing widgets");
-  nsPoint refPointAppUnits(aPresContext->DevPixelsToAppUnits(aPt.x),
-                           aPresContext->DevPixelsToAppUnits(aPt.y));
-  return refPointAppUnits - viewToWidget - aView->GetOffsetTo(baseView);
+  nsPoint viewOffset;
+  nsIWidget* viewWidget = aView->GetNearestWidget(&viewOffset);
+
+  nsIWidget* fromRoot;
+  nsPoint fromOffset = GetWidgetOffset(aWidget, fromRoot);
+  nsIWidget* toRoot;
+  nsPoint toOffset = GetWidgetOffset(viewWidget, toRoot);
+
+  nsIntPoint widgetPoint;
+  if (fromRoot == toRoot) {
+    widgetPoint = aPt + fromOffset - toOffset;
+  } else {
+    nsIntRect widgetRect(0, 0, 0, 0);
+    nsIntRect screenRect;
+    aWidget->WidgetToScreen(widgetRect, screenRect);
+    viewWidget->ScreenToWidget(screenRect, widgetRect);
+    widgetPoint = aPt + widgetRect.TopLeft();
+  }
+
+  nsPoint widgetAppUnits(aPresContext->DevPixelsToAppUnits(widgetPoint.x),
+                         aPresContext->DevPixelsToAppUnits(widgetPoint.y));
+  return widgetAppUnits - viewOffset;
 }
 
 // Combine aNewBreakType with aOrigBreakType, but limit the break types