Stop displaying layers with non-invertible transforms.

cc/trees/layer_tree_host_common.cc

 // Copyright 2011 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/trees/layer_tree_host_common.h"
 
 #include <algorithm>
 
 #include "base/debug/trace_event.h"
 #include "cc/base/math_util.h"
@@ skipping 460 matching lines @@
   bool can_accept_input = !layer->touch_event_handler_region().IsEmpty() ||
       layer->have_wheel_event_handlers();
   if (!layer->DrawsContent() && !can_accept_input)
     return true;
 
   return false;
 }
 
 static inline bool SubtreeShouldBeSkipped(LayerImpl* layer,
                                           bool layer_is_drawn) {
+  // If the layer transform is not invertible, it should not be drawn.
+  if (!layer->transform_is_invertible() && !layer->TransformIsAnimating())
+    return true;
+
   // When we need to do a readback/copy of a layer's output, we can not skip
   // it or any of its ancestors.
   if (layer->draw_properties().layer_or_descendant_has_copy_request)
     return false;
 
   // If the layer is not drawn, then skip it and its subtree.
   if (!layer_is_drawn)
     return true;
 
   // If layer is on the pending tree and opacity is being animated then
   // this subtree can't be skipped as we need to create, prioritize and
   // include tiles for this layer when deciding if tree can be activated.
   if (layer->layer_tree_impl()->IsPendingTree() && layer->OpacityIsAnimating())
     return false;
 
   // The opacity of a layer always applies to its children (either implicitly
   // via a render surface or explicitly if the parent preserves 3D), so the
   // entire subtree can be skipped if this layer is fully transparent.
   // TODO(sad): Don't skip layers used for hit testing crbug.com/295295.
   return !layer->opacity();
 }
 
 static inline bool SubtreeShouldBeSkipped(Layer* layer, bool layer_is_drawn) {
+  // If the layer transform is not invertible, it should not be drawn.
+  // TODO(ajuma): Correctly process subtrees with singular transform for the
+  // case where we may animate to a non-singular transform and wish to
+  // pre-raster.

[ajuma, 2014/04/16 19:24:49]

This TODO should move to the previous function (the LayerImpl version).

[avallee, 2014/04/16 19:33:25]

Done.

+  if (!layer->transform_is_invertible() && !layer->TransformIsAnimating())
+    return true;
+
   // When we need to do a readback/copy of a layer's output, we can not skip
   // it or any of its ancestors.
   if (layer->draw_properties().layer_or_descendant_has_copy_request)
     return false;
 
   // If the layer is not drawn, then skip it and its subtree.
   if (!layer_is_drawn)
     return true;
 
   // If the opacity is being animated then the opacity on the main thread is
@@ skipping 644 matching lines @@
 
 // Recursively walks the layer tree to compute any information that is needed
 // before doing the main recursion.
 template <typename LayerType>
 static void PreCalculateMetaInformation(
     LayerType* layer,
     PreCalculateMetaInformationRecursiveData* recursive_data) {
   bool has_delegated_content = layer->HasDelegatedContent();
   int num_descendants_that_draw_content = 0;
 
+  if (!layer->transform_is_invertible()) {
+    // Layers with singular transforms should not be drawn, the whole subtree
+    // can be skipped.
+    return;
+  }
+
   if (has_delegated_content) {
     // Layers with delegated content need to be treated as if they have as
     // many children as the number of layers they own delegated quads for.
     // Since we don't know this number right now, we choose one that acts like
     // infinity for our purposes.
     num_descendants_that_draw_content = 1000;
   }
 
   layer->draw_properties().sorted_for_recursion = false;
   layer->draw_properties().has_child_with_a_scroll_parent = false;
@@ skipping 1337 matching lines @@
   // At this point, we think the point does hit the touch event handler region
   // on the layer, but we need to walk up the parents to ensure that the layer
   // was not clipped in such a way that the hit point actually should not hit
   // the layer.
   if (PointIsClippedBySurfaceOrClipRect(screen_space_point, layer_impl))
     return false;
 
   return true;
 }
 }  // namespace cc