Changeset 136174 in webkit

Timestamp:

Nov 29, 2012, 3:21:09 PM (14 years ago)

Author:

Simon Fraser

Message:

Avoid painting lots of small rects in WebLayer painting
​https://bugs.webkit.org/show_bug.cgi?id=103673

Reviewed by Tim Horton.

r109186 added code in drawLayerContents() to enumerate over the rects in
the CALayer's dirty region, and paint them individually. This was done
to help performance on the IE Maze Solver test.

On large, complex pages like Facebook, the overhead of traversing the
RenderLayer tree for painting is such that it's better to paint a single,
or fewer rects rather than lots of little ones.

So adopt a heuristic similar to that in DrawingArea, where if the
combined area of the small rects is 75% or more of the combined rect,
just paint the combined rect. Also paint the combined rect if there
are more than 5 individual rects.

I verified that this preserves the optimization for IE Maze Solver.

• platform/graphics/mac/WebLayer.mm:

(drawLayerContents):

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• platform/graphics/mac/WebLayer.mm (modified) (1 diff)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2012-11-29  Simon Fraser  <simon.fraser@apple.com>
+
+        Avoid painting lots of small rects in WebLayer painting
+        https://bugs.webkit.org/show_bug.cgi?id=103673
+
+        Reviewed by Tim Horton.
+
+        r109186 added code in drawLayerContents() to enumerate over the rects in
+        the CALayer's dirty region, and paint them individually. This was done
+        to help performance on the IE Maze Solver test.
+        
+        On large, complex pages like Facebook, the overhead of traversing the
+        RenderLayer tree for painting is such that it's better to paint a single,
+        or fewer rects rather than lots of little ones.
+        
+        So adopt a heuristic similar to that in DrawingArea, where if the
+        combined area of the small rects is 75% or more of the combined rect,
+        just paint the combined rect. Also paint the combined rect if there
+        are more than 5 individual rects.
+        
+        I verified that this preserves the optimization for IE Maze Solver.
+
+        * platform/graphics/mac/WebLayer.mm:
+        (drawLayerContents):
+
 2012-11-29  Eugene Klyuchnikov  <eustas@chromium.org>
 

trunk/Source/WebCore/platform/graphics/mac/WebLayer.mm

@@ -86 +86 @@
 
 #if PLATFORM(IOS) || __MAC_OS_X_VERSION_MIN_REQUIRED >= 1070
-    __block GraphicsContext* ctx = &graphicsContext;
-
-    wkCALayerEnumerateRectsBeingDrawnWithBlock(layer, context, ^(CGRect rect){
-        FloatRect rectBeingDrawn(rect);
-        rectBeingDrawn.intersect(clipBounds);
-        
-        GraphicsContextStateSaver stateSaver(*ctx);
-        ctx->clip(rectBeingDrawn);
-        
-        layerContents->platformCALayerPaintContents(*ctx, enclosingIntRect(rectBeingDrawn));
+    const float wastedSpaceThreshold = 0.75f;
+    const unsigned maxRectsToPaint = 5;
+
+    double clipArea = clipBounds.width() * clipBounds.height();
+    __block double totalRectArea = 0;
+    __block unsigned rectCount = 0;
+    __block Vector<FloatRect, maxRectsToPaint> dirtyRects;
+    
+    wkCALayerEnumerateRectsBeingDrawnWithBlock(layer, context, ^(CGRect rect) {
+        if (++rectCount > maxRectsToPaint)
+            return;
+
+        totalRectArea += rect.size.width * rect.size.height;
+        dirtyRects.append(rect);
     });
+
+    if (rectCount < maxRectsToPaint && totalRectArea < clipArea * wastedSpaceThreshold) {
+        for (unsigned i = 0; i < rectCount; ++i) {
+            const FloatRect& currentRect = dirtyRects[i];
+            
+            GraphicsContextStateSaver stateSaver(graphicsContext);
+            graphicsContext.clip(currentRect);
+            
+            layerContents->platformCALayerPaintContents(graphicsContext, enclosingIntRect(currentRect));
+        }
+    } else {
+        // CGContextGetClipBoundingBox() gives us the bounds of the dirty region, so clipBounds
+        // encompasses all the dirty rects.
+        layerContents->platformCALayerPaintContents(graphicsContext, enclosingIntRect(clipBounds));
+    }
 
 #else