cc: Simplify the logic for deciding to update tile priorities.

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"
@@ skipping 198 matching lines @@
   // better scheme would be to maintain a tighter visibleContentRect for the
   // finer tilings.
   CleanUpTilingsOnActiveLayer(seen_tilings);
 }
 
 void PictureLayerImpl::dumpLayerProperties(std::string*, int indent) const {
   // TODO(enne): implement me
 }
 
 void PictureLayerImpl::updateTilePriorities() {
+  if (!tilings_->num_tilings()) {
+    last_screen_space_transform_ = screenSpaceTransform();
+    last_bounds_ = bounds();
+    last_content_bounds_ = contentBounds();
+    last_content_scale_ = contentsScaleX();
+    return;
+  }
+
   int current_source_frame_number = layerTreeImpl()->source_frame_number();
   double current_frame_time =
       (layerTreeImpl()->CurrentFrameTime() - base::TimeTicks()).InSecondsF();
 
   gfx::Transform current_screen_space_transform =
       screenSpaceTransform();
 
   gfx::Rect viewport_in_content_space;
   gfx::Transform screenToLayer(gfx::Transform::kSkipInitialization);
   if (screenSpaceTransform().GetInverse(&screenToLayer)) {
     gfx::Rect device_viewport(layerTreeImpl()->device_viewport_size());
     viewport_in_content_space = gfx::ToEnclosingRect(
         MathUtil::projectClippedRect(screenToLayer, device_viewport));
   }
 

[ccameron, 2013/02/14 18:35:10]

It'd be really nice to (in a separate change) have something where we can see
how far the layer is from the viewport, and if sufficiently far away, just say
tilings_->SetTilePrioritiesToUnimportant(). If we could do that, it would get
Digg going much faster.

I'd also like to get those unimportant tiles out of the TileManager as well
(though that is less clear).

[danakj, 2013/02/14 18:41:24]

Yeh, this is just a way to avoid the matrix inverse and project for layers
without tilings, and to not update tile properties so much.

You're right if you're dirty every frame from a scroll this isn't a silver
bullet (tho will still help for layers without content).

   WhichTree tree = layerTreeImpl()->IsActiveTree() ? ACTIVE_TREE : PENDING_TREE;
   bool store_screen_space_quads_on_tiles =
       layerTreeImpl()->debug_state().traceAllRenderedFrames;
   tilings_->UpdateTilePriorities(
       tree,
       layerTreeImpl()->device_viewport_size(),
       viewport_in_content_space,
       last_bounds_,
       bounds(),
       last_content_bounds_,
@@ skipping 483 matching lines @@
   return twin;
 }
 
 void PictureLayerImpl::getDebugBorderProperties(
     SkColor* color, float* width) const {
   *color = DebugColors::TiledContentLayerBorderColor();
   *width = DebugColors::TiledContentLayerBorderWidth(layerTreeImpl());
 }
 
 }  // namespace cc