bug #10503's test case didn't display correctly, because sibling clipping wasn't working properly. fixed CalcWindowRegions() to correctly transform sibling rectangles into widget coordinates, and to subtract only siblings that are in front of the child window.

widget/src/mac/nsChildWindow.cpp

@@ -75,75 +75,38 @@ void nsChildWindow::CalcWindowRegions()
 {
 	Inherited::CalcWindowRegions();
 
-#if 0	//¥REVISIT: this code can probably be removed: the children 
-		// are already clipped out in nsWindow::CalcWindowRegions()
-	// clip the children out of the visRgn
-	if (mClipChildren)
-	{
-		RgnHandle childRgn = ::NewRgn();
-		if (!childRgn) return;
-
-		nsCOMPtr<nsIEnumerator> children(dont_AddRef(GetChildren()));
-		if (children)
-		{
-			children->First();
-			do
-			{
-				nsISupports* child;
-				if (NS_SUCCEEDED(children->CurrentItem(&child)))
-				{
-					nsWindow* childWindow = static_cast<nsWindow*>(child);
-					NS_RELEASE(child);
-
-					nsRect childRect;
-					childWindow->GetBounds(childRect);
+	// clip the siblings out of the window region and visRegion 
+	if (mClipSiblings && mParent) {
+		// need to walk the siblings backwards, to get clipping right.
+		nsCOMPtr<nsIBidirectionalEnumerator> siblings = getter_AddRefs((nsIBidirectionalEnumerator*)mParent->GetChildren());
+		if (siblings && NS_SUCCEEDED(siblings->Last())) {
+			StRegionFromPool siblingRgn;
+			if (siblingRgn == nsnull)
+				return;
+			do {
+				// when we reach ourself, stop clipping.
+				nsCOMPtr<nsISupports> item;
+				if (NS_FAILED(siblings->CurrentItem(getter_AddRefs(item))) || item == this)
+					break;
+				
+				nsCOMPtr<nsIWidget> sibling(do_QueryInterface(item));
+				PRBool visible;
+				sibling->IsVisible(visible);
+				if (visible) {	// don't clip if not visible.
+					// get sibling's bounds in parent's coordinate system.
+					nsRect siblingRect;
+					sibling->GetBounds(siblingRect);
+					
+					// transform from parent's coordinate system to widget coordinates.
+					siblingRect.MoveBy(-mBounds.x, -mBounds.y);
 
 					Rect macRect;
-					::SetRect(&macRect, childRect.x, childRect.y, childRect.XMost(), childRect.YMost());
-					::RectRgn(childRgn, &macRect);
-					::DiffRgn(mVisRegion, childRgn, mVisRegion);
+					::SetRect(&macRect, siblingRect.x, siblingRect.y, siblingRect.XMost(), siblingRect.YMost());
+					::RectRgn(siblingRgn, &macRect);
+					::DiffRgn(mWindowRegion, siblingRgn, mWindowRegion);
+					::DiffRgn(mVisRegion, siblingRgn, mVisRegion);
 				}
-			} while (NS_SUCCEEDED(children->Next()));
-		}
-		::DisposeRgn(childRgn);
-	}
-#endif
-
-	// clip the siblings out of the window region and visRegion 
-	if (mClipSiblings && mParent)
-	{
-		nsCOMPtr<nsIEnumerator> children(dont_AddRef(mParent->GetChildren()));
-		if (children)
-		{
-			StRegionFromPool siblingRgn;
-			if (siblingRgn != nsnull) {
-				children->First();
-				do
-				{
-					nsISupports* child;
-					if (NS_SUCCEEDED(children->CurrentItem(&child)))
-					{
-						nsWindow* childWindow = static_cast<nsWindow*>(child);
-						NS_RELEASE(child);
-						
-						PRBool visible;
-						childWindow->IsVisible(visible);
-
-						if (visible && childWindow != this)	// don't clip myself
-						{
-							nsRect childRect;
-							childWindow->GetBounds(childRect);
-
-							Rect macRect;
-							::SetRect(&macRect, childRect.x, childRect.y, childRect.XMost(), childRect.YMost());
-							::RectRgn(siblingRgn, &macRect);
-							::DiffRgn(mWindowRegion, siblingRgn, mWindowRegion);
-							::DiffRgn(mVisRegion, siblingRgn, mVisRegion);
-						}
-					}
-				} while (NS_SUCCEEDED(children->Next()));
-			}
+			} while (NS_SUCCEEDED(siblings->Prev()));
 		}
 	}
 }
-