Re-raster during scale animations for GPU-rasterized layers without text

cc/layers/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/layers/picture_layer_impl.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "base/debug/trace_event_argument.h"
@@ skipping 1005 matching lines @@
   high_res->set_resolution(HIGH_RESOLUTION);
 
   SanityCheckTilingState();
 }
 
 bool PictureLayerImpl::ShouldAdjustRasterScale() const {
   if (was_screen_space_transform_animating_ !=
       draw_properties().screen_space_transform_is_animating)
     return true;
 
+  if (draw_properties().screen_space_transform_is_animating &&
+      raster_contents_scale_ != ideal_contents_scale_ &&
+      ShouldAdjustRasterScaleDuringScaleAnimations())
+    return true;
+
   bool is_pinching = layer_tree_impl()->PinchGestureActive();
   if (is_pinching && raster_page_scale_) {
     // We change our raster scale when it is:
     // - Higher than ideal (need a lower-res tiling available)
     // - Too far from ideal (need a higher-res tiling available)
     float ratio = ideal_page_scale_ / raster_page_scale_;
     if (raster_page_scale_ > ideal_page_scale_ ||
         ratio > kMaxScaleRatioDuringPinch)
       return true;
   }
@@ skipping 74 matching lines @@
         zooming_out ? old_raster_contents_scale / kMaxScaleRatioDuringPinch
                     : old_raster_contents_scale * kMaxScaleRatioDuringPinch;
     raster_contents_scale_ = SnappedContentsScale(desired_contents_scale);
     raster_page_scale_ =
         raster_contents_scale_ / raster_device_scale_ / raster_source_scale_;
   }
 
   raster_contents_scale_ =
       std::max(raster_contents_scale_, MinimumContentsScale());
 
-  // Since we're not re-rasterizing during animation, rasterize at the maximum
+  // If we're not re-rasterizing during animation, rasterize at the maximum
   // scale that will occur during the animation, if the maximum scale is
   // known. However, to avoid excessive memory use, don't rasterize at a scale
   // at which this layer would become larger than the viewport.
-  if (draw_properties().screen_space_transform_is_animating) {
+  if (draw_properties().screen_space_transform_is_animating &&
+      !ShouldAdjustRasterScaleDuringScaleAnimations()) {
     bool can_raster_at_maximum_scale = false;
     if (draw_properties().maximum_animation_contents_scale > 0.f) {
       gfx::Size bounds_at_maximum_scale = gfx::ToCeiledSize(gfx::ScaleSize(
           bounds(), draw_properties().maximum_animation_contents_scale));
       if (bounds_at_maximum_scale.GetArea() <=
           layer_tree_impl()->device_viewport_size().GetArea())
         can_raster_at_maximum_scale = true;
     }
     if (can_raster_at_maximum_scale) {
       raster_contents_scale_ =
@@ skipping 157 matching lines @@
   }
   if (tilings_->num_tilings() == 0)
     return;
 
   // MarkVisibleResourcesAsRequired depends on having exactly 1 high res
   // tiling to mark its tiles as being required for activation.
   DCHECK_EQ(1, tilings_->NumHighResTilings());
 #endif
 }
 
+bool PictureLayerImpl::ShouldAdjustRasterScaleDuringScaleAnimations() const {
+  if (!layer_tree_impl()->use_gpu_rasterization())
+    return false;
+  if (pile_->has_text())

[enne (OOO), 2014/08/20 18:15:49]

Can you add some comments about why this is needed? As far as I know, this is a
performance workaround for the fact that Ganesh is slow to reraster text at
different scales.  Is there a bug that can be linked to?

[ajuma, 2014/08/20 18:51:29]

Done.

+    return false;
+
+  return true;
+}
+
 float PictureLayerImpl::MaximumTilingContentsScale() const {
   float max_contents_scale = MinimumContentsScale();
   for (size_t i = 0; i < tilings_->num_tilings(); ++i) {
     const PictureLayerTiling* tiling = tilings_->tiling_at(i);
     max_contents_scale = std::max(max_contents_scale, tiling->contents_scale());
   }
   return max_contents_scale;
 }
 
 void PictureLayerImpl::UpdateIdealScales() {
@@ skipping 385 matching lines @@
       PictureLayerTilingSet::TilingRange tiling_range = CurrentTilingRange();
       size_t current_tiling_range_offset = current_tiling_ - tiling_range.start;
       return tiling_range.end - 1 - current_tiling_range_offset;
     }
   }
   NOTREACHED();
   return 0;
 }
 
 }  // namespace cc