Bug 526394. Part 23: Make nsRect::IntersectRect preserve height and w…

…idth if possible even when the intersection of two rectangles is empty. r=mats

gfx/src/nsRect.cpp

@@ -78,20 +78,20 @@ PRBool nsRect::IntersectRect(const nsRect &aRect1, const nsRect &aRect2)
   // Compute the destination width
   temp = PR_MIN(xmost1, xmost2);
   if (temp <= x) {
-    Empty();
-    return PR_FALSE;
+    width = 0;
+  } else {
+    width = temp - x;
   }
-  width = temp - x;
 
   // Compute the destination height
   temp = PR_MIN(ymost1, ymost2);
   if (temp <= y) {
-    Empty();
-    return PR_FALSE;
+    height = 0;
+  } else {
+    height = temp - y;
   }
-  height = temp - y;
 
-  return PR_TRUE;
+  return !IsEmpty();
 }
 
 // Computes the smallest rectangle that contains both aRect1 and aRect2 and

layout/base/nsCSSRendering.cpp

@@ -2021,7 +2021,9 @@ nsCSSRendering::PaintGradient(nsPresContext* aPresContext,
   // up by drawing tiles into temporary surfaces and copying those to the
   // destination, but after pixel-snapping tiles may not all be the same size.
   nsRect dirty;
-  dirty.IntersectRect(aDirtyRect, aFillArea);
+  if (!dirty.IntersectRect(aDirtyRect, aFillArea))
+    return;
+
   gfxRect areaToFill = RectToGfxRect(aFillArea, appUnitsPerPixel);
   gfxMatrix ctm = ctx->CurrentMatrix();
 

layout/xul/base/src/nsMenuPopupFrame.cpp

@@ -1050,8 +1050,8 @@ nsMenuPopupFrame::SetPopupPosition(nsIFrame* aAnchorFrame)
 
   // ensure that anchorRect is on screen
   if (!anchorRect.IntersectRect(anchorRect, screenRect)) {
+    anchorRect.width = anchorRect.height = 0;
     // if the anchor isn't within the screen, move it to the edge of the screen.
-    // IntersectRect will have set both the width and height of anchorRect to 0.
     if (anchorRect.x < screenRect.x)
       anchorRect.x = screenRect.x;
     if (anchorRect.XMost() > screenRect.XMost())