cc/trees/draw_property_utils.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "cc/trees/draw_property_utils.h"
   6
   7 #include <vector>
   8
   9 #include "cc/base/math_util.h"
  10 #include "cc/layers/layer.h"
  11 #include "cc/layers/layer_impl.h"
  12 #include "cc/trees/layer_tree_impl.h"
  13 #include "cc/trees/property_tree.h"
  14 #include "cc/trees/property_tree_builder.h"
  15 #include "ui/gfx/geometry/rect_conversions.h"
  16
  17 namespace cc {
  18
  19 namespace {
  20
  21 template <typename LayerType>
  22 void CalculateVisibleRects(const std::vector<LayerType*>& visible_layer_list,
  23                            const ClipTree& clip_tree,
  24                            const TransformTree& transform_tree) {
  25   for (auto& layer : visible_layer_list) {
  26     // TODO(ajuma): Compute content_scale rather than using it. Note that for
  27     // PictureLayer and PictureImageLayers, content_bounds == bounds and
  28     // content_scale_x == content_scale_y == 1.0, so once impl painting is on
  29     // everywhere, this code will be unnecessary.
  30     gfx::Size layer_bounds = layer->bounds();
  31     const bool has_clip = layer->clip_tree_index() > 0;
  32     const TransformNode* transform_node =
  33         transform_tree.Node(layer->transform_tree_index());
  34     if (has_clip) {
  35       const ClipNode* clip_node = clip_tree.Node(layer->clip_tree_index());
  36       const TransformNode* clip_transform_node =
  37           transform_tree.Node(clip_node->data.transform_id);
  38       const bool target_is_root_surface =
  39           transform_node->data.content_target_id == 1;
  40       // When the target is the root surface, we need to include the root
  41       // transform by walking up to the root of the transform tree.
  42       const int target_id =
  43           target_is_root_surface ? 0 : transform_node->data.content_target_id;
  44       const TransformNode* target_node = transform_tree.Node(target_id);
  45
  46       gfx::Transform content_to_target = transform_node->data.to_target;
  47
  48       content_to_target.Translate(layer->offset_to_transform_parent().x(),
  49                                   layer->offset_to_transform_parent().y());
  50
  51       gfx::Rect clip_rect_in_target_space;
  52       gfx::Transform clip_to_target;
  53       bool success = true;
  54       if (clip_transform_node->data.target_id == target_node->id) {
  55         clip_to_target = clip_transform_node->data.to_target;
  56       } else {
  57         success = transform_tree.ComputeTransformWithDestinationSublayerScale(
  58             clip_transform_node->id, target_node->id, &clip_to_target);
  59       }
  60
  61       if (target_node->id > clip_node->data.transform_id) {
  62         if (!success) {
  63           DCHECK(target_node->data.to_screen_is_animated);
  64
  65           // An animated singular transform may become non-singular during the
  66           // animation, so we still need to compute a visible rect. In this
  67           // situation, we treat the entire layer as visible.
  68           layer->set_visible_rect_from_property_trees(gfx::Rect(layer_bounds));
  69           continue;
  70         }
  71
  72         clip_rect_in_target_space =
  73             gfx::ToEnclosingRect(MathUtil::ProjectClippedRect(
  74                 clip_to_target, clip_node->data.combined_clip));
  75       } else {
  76         // Computing a transform to an ancestor should always succeed.
  77         DCHECK(success);
  78         clip_rect_in_target_space =
  79             gfx::ToEnclosingRect(MathUtil::MapClippedRect(
  80                 clip_to_target, clip_node->data.combined_clip));
  81       }
  82
  83       gfx::Rect layer_content_rect = gfx::Rect(layer_bounds);
  84       gfx::Rect layer_content_bounds_in_target_space =
  85           MathUtil::MapEnclosingClippedRect(content_to_target,
  86                                             layer_content_rect);
  87       clip_rect_in_target_space.Intersect(layer_content_bounds_in_target_space);
  88       if (clip_rect_in_target_space.IsEmpty()) {
  89         layer->set_visible_rect_from_property_trees(gfx::Rect());
  90         continue;
  91       }
  92
  93       gfx::Transform target_to_content;
  94       gfx::Transform target_to_layer;
  95
  96       if (transform_node->data.ancestors_are_invertible) {
  97         target_to_layer = transform_node->data.from_target;
  98         success = true;
  99       } else {
 100         success = transform_tree.ComputeTransformWithSourceSublayerScale(
 101             target_node->id, transform_node->id, &target_to_layer);
 102       }
 103
 104       if (!success) {
 105         DCHECK(transform_node->data.to_screen_is_animated);
 106
 107         // An animated singular transform may become non-singular during the
 108         // animation, so we still need to compute a visible rect. In this
 109         // situation, we treat the entire layer as visible.
 110         layer->set_visible_rect_from_property_trees(gfx::Rect(layer_bounds));
 111         continue;
 112       }
 113
 114       target_to_content.Translate(-layer->offset_to_transform_parent().x(),
 115                                   -layer->offset_to_transform_parent().y());
 116       target_to_content.PreconcatTransform(target_to_layer);
 117
 118       gfx::Rect visible_rect = MathUtil::ProjectEnclosingClippedRect(
 119           target_to_content, clip_rect_in_target_space);
 120
 121       visible_rect.Intersect(gfx::Rect(layer_bounds));
 122
 123       layer->set_visible_rect_from_property_trees(visible_rect);
 124     } else {
 125       layer->set_visible_rect_from_property_trees(gfx::Rect(layer_bounds));
 126     }
 127   }
 128 }
 129
 130 template <typename LayerType>
 131 static bool IsRootLayerOfNewRenderingContext(LayerType* layer) {
 132   if (layer->parent())
 133     return !layer->parent()->Is3dSorted() && layer->Is3dSorted();
 134   return layer->Is3dSorted();
 135 }
 136
 137 template <typename LayerType>
 138 static inline bool LayerIsInExisting3DRenderingContext(LayerType* layer) {
 139   return layer->Is3dSorted() && layer->parent() &&
 140          layer->parent()->Is3dSorted();
 141 }
 142
 143 template <typename LayerType>
 144 static bool TransformToScreenIsKnown(LayerType* layer,
 145                                      const TransformTree& tree) {
 146   const TransformNode* node = tree.Node(layer->transform_tree_index());
 147   return !node->data.to_screen_is_animated;
 148 }
 149
 150 template <typename LayerType>
 151 static bool HasSingularTransform(LayerType* layer, const TransformTree& tree) {
 152   const TransformNode* node = tree.Node(layer->transform_tree_index());
 153   return !node->data.is_invertible || !node->data.ancestors_are_invertible;
 154 }
 155
 156 template <typename LayerType>
 157 static bool IsLayerBackFaceVisible(LayerType* layer,
 158                                    const TransformTree& tree) {
 159   // The current W3C spec on CSS transforms says that backface visibility should
 160   // be determined differently depending on whether the layer is in a "3d
 161   // rendering context" or not. For Chromium code, we can determine whether we
 162   // are in a 3d rendering context by checking if the parent preserves 3d.
 163
 164   if (LayerIsInExisting3DRenderingContext(layer))
 165     return DrawTransformFromPropertyTrees(layer, tree).IsBackFaceVisible();
 166
 167   // In this case, either the layer establishes a new 3d rendering context, or
 168   // is not in a 3d rendering context at all.
 169   return layer->transform().IsBackFaceVisible();
 170 }
 171
 172 template <typename LayerType>
 173 static bool IsAnimatingTransformToScreen(LayerType* layer,
 174                                          const TransformTree& tree) {
 175   const TransformNode* node = tree.Node(layer->transform_tree_index());
 176   return node->data.to_screen_is_animated;
 177 }
 178
 179 static inline bool TransformToScreenIsKnown(Layer* layer,
 180                                             const TransformTree& tree) {
 181   return !IsAnimatingTransformToScreen(layer, tree);
 182 }
 183
 184 static inline bool TransformToScreenIsKnown(LayerImpl* layer,
 185                                             const TransformTree& tree) {
 186   return true;
 187 }
 188
 189 template <typename LayerType>
 190 static bool HasInvertibleOrAnimatedTransform(LayerType* layer) {
 191   return layer->transform_is_invertible() || layer->TransformIsAnimating();
 192 }
 193
 194 static inline bool SubtreeShouldBeSkipped(LayerImpl* layer,
 195                                           bool layer_is_drawn) {
 196   // If the layer transform is not invertible, it should not be drawn.
 197   // TODO(ajuma): Correctly process subtrees with singular transform for the
 198   // case where we may animate to a non-singular transform and wish to
 199   // pre-raster.
 200   if (!HasInvertibleOrAnimatedTransform(layer))
 201     return true;
 202
 203   // When we need to do a readback/copy of a layer's output, we can not skip
 204   // it or any of its ancestors.
 205   if (layer->draw_properties().layer_or_descendant_has_copy_request)
 206     return false;
 207
 208   // We cannot skip the the subtree if a descendant has a wheel or touch handler
 209   // or the hit testing code will break (it requires fresh transforms, etc).
 210   if (layer->draw_properties().layer_or_descendant_has_input_handler)
 211     return false;
 212
 213   // If the layer is not drawn, then skip it and its subtree.
 214   if (!layer_is_drawn)
 215     return true;
 216
 217   // If layer is on the pending tree and opacity is being animated then
 218   // this subtree can't be skipped as we need to create, prioritize and
 219   // include tiles for this layer when deciding if tree can be activated.
 220   if (layer->layer_tree_impl()->IsPendingTree() && layer->OpacityIsAnimating())
 221     return false;
 222
 223   // The opacity of a layer always applies to its children (either implicitly
 224   // via a render surface or explicitly if the parent preserves 3D), so the
 225   // entire subtree can be skipped if this layer is fully transparent.
 226   return !layer->opacity();
 227 }
 228
 229 static inline bool SubtreeShouldBeSkipped(Layer* layer, bool layer_is_drawn) {
 230   // If the layer transform is not invertible, it should not be drawn.
 231   if (!layer->transform_is_invertible() && !layer->TransformIsAnimating())
 232     return true;
 233
 234   // When we need to do a readback/copy of a layer's output, we can not skip
 235   // it or any of its ancestors.
 236   if (layer->draw_properties().layer_or_descendant_has_copy_request)
 237     return false;
 238
 239   // We cannot skip the the subtree if a descendant has a wheel or touch handler
 240   // or the hit testing code will break (it requires fresh transforms, etc).
 241   if (layer->draw_properties().layer_or_descendant_has_input_handler)
 242     return false;
 243
 244   // If the layer is not drawn, then skip it and its subtree.
 245   if (!layer_is_drawn)
 246     return true;
 247
 248   // If the opacity is being animated then the opacity on the main thread is
 249   // unreliable (since the impl thread may be using a different opacity), so it
 250   // should not be trusted.
 251   // In particular, it should not cause the subtree to be skipped.
 252   // Similarly, for layers that might animate opacity using an impl-only
 253   // animation, their subtree should also not be skipped.
 254   return !layer->opacity() && !layer->OpacityIsAnimating() &&
 255          !layer->OpacityCanAnimateOnImplThread();
 256 }
 257
 258 template <typename LayerType>
 259 static bool LayerShouldBeSkipped(LayerType* layer,
 260                                  bool layer_is_drawn,
 261                                  const TransformTree& tree) {
 262   // Layers can be skipped if any of these conditions are met.
 263   //   - is not drawn due to it or one of its ancestors being hidden (or having
 264   //     no copy requests).
 265   //   - does not draw content.
 266   //   - is transparent.
 267   //   - has empty bounds
 268   //   - the layer is not double-sided, but its back face is visible.
 269   //
 270   // Some additional conditions need to be computed at a later point after the
 271   // recursion is finished.
 272   //   - the intersection of render_surface content and layer clip_rect is empty
 273   //   - the visible_layer_rect is empty
 274   //
 275   // Note, if the layer should not have been drawn due to being fully
 276   // transparent, we would have skipped the entire subtree and never made it
 277   // into this function, so it is safe to omit this check here.
 278   if (!layer_is_drawn)
 279     return true;
 280
 281   if (!layer->DrawsContent() || layer->bounds().IsEmpty())
 282     return true;
 283
 284   LayerType* backface_test_layer = layer;
 285   if (layer->use_parent_backface_visibility()) {
 286     DCHECK(layer->parent());
 287     DCHECK(!layer->parent()->use_parent_backface_visibility());
 288     backface_test_layer = layer->parent();
 289   }
 290
 291   // The layer should not be drawn if (1) it is not double-sided and (2) the
 292   // back of the layer is known to be facing the screen.
 293   if (!backface_test_layer->double_sided() &&
 294       TransformToScreenIsKnown(backface_test_layer, tree) &&
 295       IsLayerBackFaceVisible(backface_test_layer, tree))
 296     return true;
 297
 298   return false;
 299 }
 300
 301 template <typename LayerType>
 302 void FindLayersThatNeedUpdates(
 303     LayerType* layer,
 304     const TransformTree& tree,
 305     bool subtree_is_visible_from_ancestor,
 306     typename LayerType::LayerListType* update_layer_list,
 307     std::vector<LayerType*>* visible_layer_list) {
 308   bool layer_is_drawn =
 309       layer->HasCopyRequest() ||
 310       (subtree_is_visible_from_ancestor && !layer->hide_layer_and_subtree());
 311
 312   if (layer->parent() && SubtreeShouldBeSkipped(layer, layer_is_drawn))
 313     return;
 314
 315   if (!LayerShouldBeSkipped(layer, layer_is_drawn, tree)) {
 316     visible_layer_list->push_back(layer);
 317     update_layer_list->push_back(layer);
 318   }
 319
 320   // Append mask layers to the update layer list.  They don't have valid visible
 321   // rects, so need to get added after the above calculation.  Replica layers
 322   // don't need to be updated.
 323   if (LayerType* mask_layer = layer->mask_layer())
 324     update_layer_list->push_back(mask_layer);
 325   if (LayerType* replica_layer = layer->replica_layer()) {
 326     if (LayerType* mask_layer = replica_layer->mask_layer())
 327       update_layer_list->push_back(mask_layer);
 328   }
 329
 330   for (size_t i = 0; i < layer->children().size(); ++i) {
 331     FindLayersThatNeedUpdates(layer->child_at(i), tree, layer_is_drawn,
 332                               update_layer_list, visible_layer_list);
 333   }
 334 }
 335
 336 }  // namespace
 337
 338 void ComputeClips(ClipTree* clip_tree, const TransformTree& transform_tree) {
 339   if (!clip_tree->needs_update())
 340     return;
 341   for (int i = 0; i < static_cast<int>(clip_tree->size()); ++i) {
 342     ClipNode* clip_node = clip_tree->Node(i);
 343
 344     // Only descendants of a real clipping layer (i.e., not 0) may have their
 345     // clip adjusted due to intersecting with an ancestor clip.
 346     const bool is_clipped = clip_node->parent_id > 0;
 347     if (!is_clipped) {
 348       clip_node->data.combined_clip = clip_node->data.clip;
 349       continue;
 350     }
 351
 352     ClipNode* parent_clip_node = clip_tree->parent(clip_node);
 353     const TransformNode* parent_transform_node =
 354         transform_tree.Node(parent_clip_node->data.transform_id);
 355     const TransformNode* transform_node =
 356         transform_tree.Node(clip_node->data.transform_id);
 357
 358     // Clips must be combined in target space. We cannot, for example, combine
 359     // clips in the space of the child clip. The reason is non-affine
 360     // transforms. Say we have the following tree T->A->B->C, and B clips C, but
 361     // draw into target T. It may be the case that A applies a perspective
 362     // transform, and B and C are at different z positions. When projected into
 363     // target space, the relative sizes and positions of B and C can shift.
 364     // Since it's the relationship in target space that matters, that's where we
 365     // must combine clips.
 366     gfx::Transform parent_to_target;
 367     gfx::Transform clip_to_target;
 368     gfx::Transform target_to_clip;
 369
 370     const bool target_is_root_surface = clip_node->data.target_id == 1;
 371     // When the target is the root surface, we need to include the root
 372     // transform by walking up to the root of the transform tree.
 373     const int target_id =
 374         target_is_root_surface ? 0 : clip_node->data.target_id;
 375
 376     bool success = true;
 377     if (parent_transform_node->data.content_target_id ==
 378         clip_node->data.target_id) {
 379       parent_to_target = parent_transform_node->data.to_target;
 380     } else {
 381       success &= transform_tree.ComputeTransformWithDestinationSublayerScale(
 382           parent_transform_node->id, target_id, &parent_to_target);
 383     }
 384
 385     if (transform_node->data.content_target_id == clip_node->data.target_id) {
 386       clip_to_target = transform_node->data.to_target;
 387     } else {
 388       success &= transform_tree.ComputeTransformWithDestinationSublayerScale(
 389           transform_node->id, target_id, &clip_to_target);
 390     }
 391
 392     if (transform_node->data.content_target_id == clip_node->data.target_id &&
 393         transform_node->data.ancestors_are_invertible) {
 394       target_to_clip = transform_node->data.from_target;
 395     } else {
 396       success &= clip_to_target.GetInverse(&target_to_clip);
 397     }
 398
 399     // If we can't compute a transform, it's because we had to use the inverse
 400     // of a singular transform. We won't draw in this case, so there's no need
 401     // to compute clips.
 402     if (!success)
 403       continue;
 404
 405     // In order to intersect with as small a rect as possible, we do a
 406     // preliminary clip in target space so that when we project back, there's
 407     // less likelihood of intersecting the view plane.
 408     gfx::RectF inherited_clip_in_target_space = MathUtil::MapClippedRect(
 409         parent_to_target, parent_clip_node->data.combined_clip);
 410
 411     gfx::RectF clip_in_target_space =
 412         MathUtil::MapClippedRect(clip_to_target, clip_node->data.clip);
 413
 414     gfx::RectF intersected_in_target_space = gfx::IntersectRects(
 415         inherited_clip_in_target_space, clip_in_target_space);
 416
 417     clip_node->data.combined_clip = MathUtil::ProjectClippedRect(
 418         target_to_clip, intersected_in_target_space);
 419
 420     clip_node->data.combined_clip.Intersect(clip_node->data.clip);
 421   }
 422   clip_tree->set_needs_update(false);
 423 }
 424
 425 void ComputeTransforms(TransformTree* transform_tree) {
 426   if (!transform_tree->needs_update())
 427     return;
 428   for (int i = 1; i < static_cast<int>(transform_tree->size()); ++i)
 429     transform_tree->UpdateTransforms(i);
 430   transform_tree->set_needs_update(false);
 431 }
 432
 433 template <typename LayerType>
 434 void ComputeVisibleRectsUsingPropertyTreesInternal(
 435     LayerType* root_layer,
 436     PropertyTrees* property_trees,
 437     typename LayerType::LayerListType* update_layer_list) {
 438   if (property_trees->transform_tree.needs_update())
 439     property_trees->clip_tree.set_needs_update(true);
 440   ComputeTransforms(&property_trees->transform_tree);
 441   ComputeClips(&property_trees->clip_tree, property_trees->transform_tree);
 442
 443   const bool subtree_is_visible_from_ancestor = true;
 444   std::vector<LayerType*> visible_layer_list;
 445   FindLayersThatNeedUpdates(root_layer, property_trees->transform_tree,
 446                             subtree_is_visible_from_ancestor, update_layer_list,
 447                             &visible_layer_list);
 448   CalculateVisibleRects<LayerType>(visible_layer_list,
 449                                    property_trees->clip_tree,
 450                                    property_trees->transform_tree);
 451 }
 452
 453 void BuildPropertyTreesAndComputeVisibleRects(
 454     Layer* root_layer,
 455     const Layer* page_scale_layer,
 456     float page_scale_factor,
 457     float device_scale_factor,
 458     const gfx::Rect& viewport,
 459     const gfx::Transform& device_transform,
 460     PropertyTrees* property_trees,
 461     LayerList* update_layer_list) {
 462   PropertyTreeBuilder::BuildPropertyTrees(
 463       root_layer, page_scale_layer, page_scale_factor, device_scale_factor,
 464       viewport, device_transform, property_trees);
 465   ComputeVisibleRectsUsingPropertyTrees(root_layer, property_trees,
 466                                         update_layer_list);
 467 }
 468
 469 void BuildPropertyTreesAndComputeVisibleRects(
 470     LayerImpl* root_layer,
 471     const LayerImpl* page_scale_layer,
 472     float page_scale_factor,
 473     float device_scale_factor,
 474     const gfx::Rect& viewport,
 475     const gfx::Transform& device_transform,
 476     PropertyTrees* property_trees,
 477     LayerImplList* update_layer_list) {
 478   PropertyTreeBuilder::BuildPropertyTrees(
 479       root_layer, page_scale_layer, page_scale_factor, device_scale_factor,
 480       viewport, device_transform, property_trees);
 481   ComputeVisibleRectsUsingPropertyTrees(root_layer, property_trees,
 482                                         update_layer_list);
 483 }
 484
 485 void ComputeVisibleRectsUsingPropertyTrees(Layer* root_layer,
 486                                            PropertyTrees* property_trees,
 487                                            LayerList* update_layer_list) {
 488   ComputeVisibleRectsUsingPropertyTreesInternal(root_layer, property_trees,
 489                                                 update_layer_list);
 490 }
 491
 492 void ComputeVisibleRectsUsingPropertyTrees(LayerImpl* root_layer,
 493                                            PropertyTrees* property_trees,
 494                                            LayerImplList* update_layer_list) {
 495   ComputeVisibleRectsUsingPropertyTreesInternal(root_layer, property_trees,
 496                                                 update_layer_list);
 497 }
 498
 499 template <typename LayerType>
 500 gfx::Transform DrawTransformFromPropertyTreesInternal(
 501     const LayerType* layer,
 502     const TransformTree& tree) {
 503   const TransformNode* node = tree.Node(layer->transform_tree_index());
 504   // TODO(vollick): ultimately we'll need to find this information (whether or
 505   // not we establish a render surface) somewhere other than the layer.
 506   const TransformNode* target_node =
 507       layer->render_surface() ? node : tree.Node(node->data.content_target_id);
 508
 509   gfx::Transform xform;
 510   const bool owns_non_root_surface = layer->parent() && layer->render_surface();
 511   if (!owns_non_root_surface) {
 512     // If you're not the root, or you don't own a surface, you need to apply
 513     // your local offset.
 514     xform = node->data.to_target;
 515     if (layer->should_flatten_transform_from_property_tree())
 516       xform.FlattenTo2d();
 517     xform.Translate(layer->offset_to_transform_parent().x(),
 518                     layer->offset_to_transform_parent().y());
 519   } else {
 520     // Surfaces need to apply their sublayer scale.
 521     xform.Scale(target_node->data.sublayer_scale.x(),
 522                 target_node->data.sublayer_scale.y());
 523   }
 524   return xform;
 525 }
 526
 527 gfx::Transform DrawTransformFromPropertyTrees(const Layer* layer,
 528                                               const TransformTree& tree) {
 529   return DrawTransformFromPropertyTreesInternal(layer, tree);
 530 }
 531
 532 gfx::Transform DrawTransformFromPropertyTrees(const LayerImpl* layer,
 533                                               const TransformTree& tree) {
 534   return DrawTransformFromPropertyTreesInternal(layer, tree);
 535 }
 536
 537 template <typename LayerType>
 538 gfx::Transform ScreenSpaceTransformFromPropertyTreesInternal(
 539     LayerType* layer,
 540     const TransformTree& tree) {
 541   gfx::Transform xform(1, 0, 0, 1, layer->offset_to_transform_parent().x(),
 542                        layer->offset_to_transform_parent().y());
 543   if (layer->transform_tree_index() >= 0) {
 544     gfx::Transform ssxform =
 545         tree.Node(layer->transform_tree_index())->data.to_screen;
 546     xform.ConcatTransform(ssxform);
 547     if (layer->should_flatten_transform_from_property_tree())
 548       xform.FlattenTo2d();
 549   }
 550   return xform;
 551 }
 552
 553 gfx::Transform ScreenSpaceTransformFromPropertyTrees(
 554     const Layer* layer,
 555     const TransformTree& tree) {
 556   return ScreenSpaceTransformFromPropertyTreesInternal(layer, tree);
 557 }
 558
 559 gfx::Transform ScreenSpaceTransformFromPropertyTrees(
 560     const LayerImpl* layer,
 561     const TransformTree& tree) {
 562   return ScreenSpaceTransformFromPropertyTreesInternal(layer, tree);
 563 }
 564
 565 template <typename LayerType>
 566 float DrawOpacityFromPropertyTreesInternal(LayerType layer,
 567                                            const OpacityTree& tree) {
 568   if (!layer->render_target())
 569     return 0.f;
 570
 571   const OpacityNode* target_node =
 572       tree.Node(layer->render_target()->opacity_tree_index());
 573   const OpacityNode* node = tree.Node(layer->opacity_tree_index());
 574   if (node == target_node)
 575     return 1.f;
 576
 577   float draw_opacity = 1.f;
 578   while (node != target_node) {
 579     draw_opacity *= node->data;
 580     node = tree.parent(node);
 581   }
 582   return draw_opacity;
 583 }
 584
 585 float DrawOpacityFromPropertyTrees(const Layer* layer,
 586                                    const OpacityTree& tree) {
 587   return DrawOpacityFromPropertyTreesInternal(layer, tree);
 588 }
 589
 590 float DrawOpacityFromPropertyTrees(const LayerImpl* layer,
 591                                    const OpacityTree& tree) {
 592   return DrawOpacityFromPropertyTreesInternal(layer, tree);
 593 }
 594
 595 }  // namespace cc