cc: Throttle tile priority updates to once a frame.

cc/picture_layer_impl.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_impl.h"
 
 #include "base/time.h"
 #include "cc/append_quads_data.h"
 #include "cc/checkerboard_draw_quad.h"
 #include "cc/debug_border_draw_quad.h"
 #include "cc/debug_colors.h"
+#include "cc/frame_rate_counter.h"
 #include "cc/layer_tree_impl.h"
 #include "cc/math_util.h"
 #include "cc/quad_sink.h"
 #include "cc/solid_color_draw_quad.h"
 #include "cc/tile_draw_quad.h"
 #include "ui/gfx/quad_f.h"
 #include "ui/gfx/rect_conversions.h"
 #include "ui/gfx/size_conversions.h"
 
 namespace {
 const float kMaxScaleRatioDuringPinch = 2.0f;
 }
 
 namespace cc {
 
 PictureLayerImpl::PictureLayerImpl(LayerTreeImpl* treeImpl, int id)
     : LayerImpl(treeImpl, id),
       pile_(PicturePileImpl::Create()),
+      last_source_frame_number_(0),
+      last_impl_frame_number_(0),
       last_update_time_(0),
       last_content_scale_(0),
       ideal_contents_scale_(0),
       is_mask_(false) {
 }
 
 PictureLayerImpl::~PictureLayerImpl() {
 }
 
 const char* PictureLayerImpl::layerTypeAsString() const {
@@ skipping 19 matching lines @@
 }
 
 void PictureLayerImpl::pushPropertiesTo(LayerImpl* base_layer) {
   LayerImpl::pushPropertiesTo(base_layer);
 
   PictureLayerImpl* layer_impl = static_cast<PictureLayerImpl*>(base_layer);
 
   layer_impl->SetIsMask(is_mask_);
   layer_impl->TransferTilingSet(tilings_.Pass());
   layer_impl->pile_ = pile_;
+  layer_impl->last_impl_frame_number_ = 0;
   pile_ = PicturePileImpl::Create();
   pile_->set_slow_down_raster_scale_factor(
       layerTreeImpl()->debug_state().slowDownRasterScaleFactor);
 }
 
 
 void PictureLayerImpl::appendQuads(QuadSink& quadSink,
                                    AppendQuadsData& appendQuadsData) {
   const gfx::Rect& rect = visibleContentRect();
   gfx::Rect content_rect(gfx::Point(), contentBounds());
@@ skipping 107 matching lines @@
   // During a pinch, a user could zoom in and out, so throwing away a tiling may
   // be premature.
   if (!layerTreeImpl()->PinchGestureActive())
     CleanUpUnusedTilings(seen_tilings);
 }
 
 void PictureLayerImpl::dumpLayerProperties(std::string*, int indent) const {
   // TODO(enne): implement me
 }
 
-void PictureLayerImpl::didUpdateTransforms() {
+void PictureLayerImpl::updateTilePriorities() {
+  int current_source_frame_number = layerTreeImpl()->source_frame_number();
+  bool first_update_in_new_source_frame =
+      current_source_frame_number > last_source_frame_number_;

[qinmin, 2013/01/25 05:07:53]

i think it is possible for current_source_frame_number to overflow, so this
statement will not be true when that happens

[danakj, 2013/01/25 05:09:01]

ya you're right, i already switched it to != in the last patch. good catch tho!

+
+  int current_impl_frame_number =
+      layerTreeImpl()->frame_rate_counter()->currentFrameNumber();
+  bool first_frame_in_new_impl_tree =
+      last_impl_frame_number_ == 0 ||
+      current_impl_frame_number == last_impl_frame_number_;
+
+  // In pending tree, this is always called. We update priorities:
+  // - Immediately after a commit (first_update_in_new_source_frame).
+  // - On animation ticks after the first frame in the tree.
+  // In active tree, this is only called during draw. We update priorities:
+  // - On draws after the first frame in the tree.
+  if (first_frame_in_new_impl_tree && !first_update_in_new_source_frame)
+    return;
+
   gfx::Transform current_screen_space_transform =
       screenSpaceTransform();
   double current_time =
       (base::TimeTicks::Now() - base::TimeTicks()).InSecondsF();
   double time_delta = 0;
   if (last_update_time_ != 0 && last_bounds_ == bounds() &&
       last_content_bounds_ == contentBounds() &&
       last_content_scale_ == contentsScaleX()) {
     time_delta = current_time - last_update_time_;
   }
   WhichTree tree = layerTreeImpl()->IsActiveTree() ? ACTIVE_TREE : PENDING_TREE;
   tilings_->UpdateTilePriorities(
       tree,
       layerTreeImpl()->device_viewport_size(),
       last_content_scale_,
       contentsScaleX(),
       last_screen_space_transform_,
       current_screen_space_transform,
       time_delta);
 
+  last_source_frame_number_ = current_source_frame_number;
+  last_impl_frame_number_ = current_impl_frame_number;
   last_screen_space_transform_ = current_screen_space_transform;
   last_update_time_ = current_time;
   last_bounds_ = bounds();
   last_content_bounds_ = contentBounds();
   last_content_scale_ = contentsScaleX();
 }
 
 void PictureLayerImpl::didBecomeActive() {
   LayerImpl::didBecomeActive();
   tilings_->DidBecomeActive();
@@ skipping 298 matching lines @@
     if (std::find(used_tilings.begin(), used_tilings.end(), tiling) ==
         used_tilings.end())
       to_remove.push_back(tiling);
   }
 
   for (size_t i = 0; i < to_remove.size(); ++i)
     tilings_->Remove(to_remove[i]);
 }
 
 }  // namespace cc