Optimize RenderLayer::intersectsDamageRect() slightly

https://bugs.webkit.org/show_bug.cgi?id=143186

Reviewed by Zalan Bujtas.

We can early return from RenderLayer::intersectsDamageRect() if the
damageRect is empty, since nothing will intersect with the empty rect.

Slight performance gain when scrolling overflow-scroll with lots of nested,
clipping layers.

* rendering/RenderLayer.cpp:
(WebCore::RenderLayer::calculateClipRects):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@182116 268f45cc-cd09-0410-ab3c-d52691b4dbfc

diff --git a/Source/WebCore/ChangeLog b/Source/WebCore/ChangeLog
index bc16668..6e5d2e1 100644 (file)
--- a/Source/WebCore/ChangeLog
+++ b/Source/WebCore/ChangeLog
@@ -1,3 +1,19 @@
+2015-03-28  Simon Fraser  <simon.fraser@apple.com>
+
+        Optimize RenderLayer::intersectsDamageRect() slightly
+        https://bugs.webkit.org/show_bug.cgi?id=143186
+
+        Reviewed by Zalan Bujtas.
+
+        We can early return from RenderLayer::intersectsDamageRect() if the
+        damageRect is empty, since nothing will intersect with the empty rect.
+        
+        Slight performance gain when scrolling overflow-scroll with lots of nested,
+        clipping layers.
+
+        * rendering/RenderLayer.cpp:
+        (WebCore::RenderLayer::calculateClipRects):
+
 2015-03-28  Anders Carlsson  <andersca@apple.com>
 
         Remove an unused SPI method from WebKitLegacy

diff --git a/Source/WebCore/rendering/RenderLayer.cpp b/Source/WebCore/rendering/RenderLayer.cpp
index 9220589..f7828ab 100644 (file)
--- a/Source/WebCore/rendering/RenderLayer.cpp
+++ b/Source/WebCore/rendering/RenderLayer.cpp
@@ -5729,6 +5729,9 @@ bool RenderLayer::intersectsDamageRect(const LayoutRect& layerBounds, const Layo
     if (isRootLayer() || renderer().isRoot())
         return true;
 
+    if (damageRect.isEmpty())
+        return false;
+
     // If we aren't an inline flow, and our layer bounds do intersect the damage rect, then we 
     // can go ahead and return true.
     if (!renderer().isRenderInline()) {