Bug 1126164 - Avoid setting clip regions on plugin windows if the same clip region was already set. r=roc

widget/gtk/nsWindow.cpp

@@ -4227,9 +4227,11 @@ nsWindow::SetWindowClipRegion(const nsTArray<nsIntRect>& aRects,
         }
     }
 
-    if (!StoreWindowClipRegion(*newRects))
+    if (IsWindowClipRegionEqual(*newRects))
         return NS_OK;
 
+    StoreWindowClipRegion(*newRects);
+
     if (!mGdkWindow)
         return NS_OK;
 

widget/nsBaseWidget.cpp

@@ -647,18 +647,21 @@ nsTransparencyMode nsBaseWidget::GetTransparencyMode() {
 }
 
 bool
+nsBaseWidget::IsWindowClipRegionEqual(const nsTArray<nsIntRect>& aRects)
+{
+  return mClipRects &&
+         mClipRectCount == aRects.Length() &&
+         memcmp(mClipRects, aRects.Elements(), sizeof(nsIntRect)*mClipRectCount) == 0;
+}
+
+void
 nsBaseWidget::StoreWindowClipRegion(const nsTArray<nsIntRect>& aRects)
 {
-  if (mClipRects && mClipRectCount == aRects.Length() &&
-      memcmp(mClipRects, aRects.Elements(), sizeof(nsIntRect)*mClipRectCount) == 0)
-    return false;
-
   mClipRectCount = aRects.Length();
   mClipRects = new nsIntRect[mClipRectCount];
   if (mClipRects) {
     memcpy(mClipRects, aRects.Elements(), sizeof(nsIntRect)*mClipRectCount);
   }
-  return true;
 }
 
 void
@@ -695,16 +698,8 @@ nsBaseWidget::SetWindowClipRegion(const nsTArray<nsIntRect>& aRects,
                                   bool aIntersectWithExisting)
 {
   if (!aIntersectWithExisting) {
-    nsBaseWidget::StoreWindowClipRegion(aRects);
+    StoreWindowClipRegion(aRects);
   } else {
-    // In this case still early return if nothing changed.
-    if (mClipRects && mClipRectCount == aRects.Length() &&
-        memcmp(mClipRects,
-               aRects.Elements(),
-               sizeof(nsIntRect)*mClipRectCount) == 0) {
-      return NS_OK;
-    }
-
     // get current rects
     nsTArray<nsIntRect> currentRects;
     GetWindowClipRegion(&currentRects);
@@ -719,7 +714,7 @@ nsBaseWidget::SetWindowClipRegion(const nsTArray<nsIntRect>& aRects,
     nsTArray<nsIntRect> rects;
     ArrayFromRegion(intersection, rects);
     // store
-    nsBaseWidget::StoreWindowClipRegion(rects);
+    StoreWindowClipRegion(rects);
   }
   return NS_OK;
 }

widget/nsBaseWidget.h

@@ -362,9 +362,12 @@ protected:
   { return NS_ERROR_NOT_IMPLEMENTED; }
 
 protected:
-  // Stores the clip rectangles in aRects into mClipRects. Returns true
-  // if the new rectangles are different from the old rectangles.
-  bool StoreWindowClipRegion(const nsTArray<nsIntRect>& aRects);
+  // Utility to check if an array of clip rects is equal to our
+  // internally stored clip rect array mClipRects.
+  bool IsWindowClipRegionEqual(const nsTArray<nsIntRect>& aRects);
+
+  // Stores the clip rectangles in aRects into mClipRects.
+  void StoreWindowClipRegion(const nsTArray<nsIntRect>& aRects);
 
   virtual already_AddRefed<nsIWidget>
   AllocateChildPopupWidget()

widget/windows/nsWindow.cpp

@@ -6440,6 +6440,10 @@ nsresult
 nsWindow::SetWindowClipRegion(const nsTArray<nsIntRect>& aRects,
                               bool aIntersectWithExisting)
 {
+  if (IsWindowClipRegionEqual(aRects)) {
+    return NS_OK;
+  }
+
   nsBaseWidget::SetWindowClipRegion(aRects, aIntersectWithExisting);
 
   HRGN dest = CreateHRGNFromArray(aRects);