Include viewport clip in visible rect of unclipped surfaces (2)

cc/trees/draw_property_utils.cc

 // Copyright 2014 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/draw_property_utils.h"
 
 #include <stddef.h>
 
 #include <vector>
 
@@ skipping 409 matching lines @@
             gfx::ToEnclosingRect(MathUtil::ProjectClippedRect(
                 target_to_content, combined_clip_rect_in_target_space));
         visible_rect.Intersect(gfx::Rect(layer_bounds));
         layer->set_visible_layer_rect(visible_rect);
       } else {
         layer->set_visible_layer_rect(gfx::Rect(layer_bounds));
       }
       continue;
     }
 
-    // When both the layer and the target are unclipped, the entire layer
-    // content rect is visible.
+    // When both the layer and the target are unclipped, we only have to apply
+    // the viewport clip.
     const bool fully_visible =
         !clip_node->layers_are_clipped && !clip_node->target_is_clipped;
 
     if (fully_visible) {
-      layer->set_visible_layer_rect(gfx::Rect(layer_bounds));
+      if (!transform_node->ancestors_are_invertible) {
+        // An animated singular transform may become non-singular during the
+        // animation, so we still need to compute a visible rect. In this
+        // situation, we treat the entire layer as visible.
+        layer->set_visible_layer_rect(gfx::Rect(layer_bounds));
+      } else {
+        gfx::Transform from_screen;
+        from_screen.Translate(-layer->offset_to_transform_parent().x(),
+                              -layer->offset_to_transform_parent().y());
+        from_screen.PreconcatTransform(
+            property_trees->transform_tree.FromScreen(transform_node->id));
+        gfx::Rect visible_rect =
+            gfx::ToEnclosingRect(MathUtil::ProjectClippedRect(
+                from_screen, property_trees->clip_tree.ViewportClip()));
+        visible_rect.Intersect(gfx::Rect(layer_bounds));
+        layer->set_visible_layer_rect(visible_rect);
+      }
       continue;
     }
 
     int target_node_id = transform_tree.ContentTargetId(transform_node->id);
 
     // The clip node stores clip rect in its target space. If required,
     // this clip rect should be mapped to the current layer's target space.
     gfx::RectF combined_clip_rect_in_target_space;
 
     if (clip_node->target_transform_id != target_node_id) {
@@ skipping 1138 matching lines @@
 void UpdateElasticOverscroll(PropertyTrees* property_trees,
                              const Layer* overscroll_elasticity_layer,
                              const gfx::Vector2dF& elastic_overscroll) {
   UpdateElasticOverscrollInternal(property_trees, overscroll_elasticity_layer,
                                   elastic_overscroll);
 }
 
 }  // namespace draw_property_utils
 
 }  // namespace cc