Clamps to invalidation region of a PictureLayer to the layer bounds to avoid adding unecessary bulk

cc/picture_layer.cc

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/picture_layer.h"
 
 #include "cc/layer_tree_impl.h"
 #include "cc/picture_layer_impl.h"
 #include "ui/gfx/rect_conversions.h"
 
@@ skipping 33 matching lines @@
 }
 
 void PictureLayer::setLayerTreeHost(LayerTreeHost* host) {
   Layer::setLayerTreeHost(host);
   if (host)
       pile_.SetMinContentsScale(host->settings().minimumContentsScale);
 }
 
 void PictureLayer::setNeedsDisplayRect(const gfx::RectF& layer_rect) {
   gfx::Rect rect = gfx::ToEnclosedRect(layer_rect);
-  pending_invalidation_.Union(rect);
+  if (!rect.IsEmpty()) {

[danakj, 2013/01/09 01:00:05]

i think this if() is kinda surplus too, everything should be no-ops without it
when the rect is empty, unless we're seeing some perf hit from this (seems
unlikely in this method?)

[vangelis, 2013/01/09 01:50:36]

it is indeed a no-op but still goes though a surprising amount of code through
SkRegion with several on-stack allocations. This method gets called quite a bit
with empty rects, when the assorted layer properties are being setup. Probably
not a significant win perf-wise but since I was passing by...

[danakj, 2013/01/09 01:51:48]

If it's an issue, maybe we should add it to cc::Region instead, so all callsites
can benefit? I'll leave that up to you.

+    // Clamp invalidation to the layer bounds.
+    rect.Intersect(gfx::Rect(contentBounds()));

[danakj, 2013/01/09 01:00:05]

Sorry to miss this last round: You want bounds() here actually, not
contentBounds(). This is all in layer space (hence layer_rect's name)

[vangelis, 2013/01/09 01:50:36]

Done.

+    pending_invalidation_.Union(rect);
+  }
   Layer::setNeedsDisplayRect(layer_rect);
 }
 
 void PictureLayer::update(ResourceUpdateQueue&, const OcclusionTracker*,
                     RenderingStats& stats) {
   if (pile_.size() == bounds() && pending_invalidation_.IsEmpty())
     return;
 
   pile_.Resize(bounds());
 
   // Calling paint in WebKit can sometimes cause invalidations, so save
   // off the invalidation prior to calling update.
   pile_invalidation_.Swap(pending_invalidation_);
   pending_invalidation_.Clear();
 
   pile_.Update(client_, pile_invalidation_, stats);
 }
 
 void PictureLayer::setIsMask(bool is_mask) {
   is_mask_ = is_mask;
 }
 
 }  // namespace cc