src/cc/trees/occlusion_tracker.cc

   1 // Copyright 2012 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/occlusion_tracker.h"
   6
   7 #include <algorithm>
   8
   9 #include "cc/base/math_util.h"
  10 #include "cc/debug/overdraw_metrics.h"
  11 #include "cc/layers/layer.h"
  12 #include "cc/layers/layer_impl.h"
  13 #include "cc/layers/render_surface.h"
  14 #include "cc/layers/render_surface_impl.h"
  15 #include "ui/gfx/quad_f.h"
  16 #include "ui/gfx/rect_conversions.h"
  17
  18 namespace cc {
  19
  20 template <typename LayerType, typename RenderSurfaceType>
  21 OcclusionTrackerBase<LayerType, RenderSurfaceType>::OcclusionTrackerBase(
  22     const gfx::Rect& screen_space_clip_rect, bool record_metrics_for_frame)
  23     : screen_space_clip_rect_(screen_space_clip_rect),
  24       overdraw_metrics_(OverdrawMetrics::Create(record_metrics_for_frame)),
  25       occluding_screen_space_rects_(NULL),
  26       non_occluding_screen_space_rects_(NULL) {}
  27
  28 template <typename LayerType, typename RenderSurfaceType>
  29 OcclusionTrackerBase<LayerType, RenderSurfaceType>::~OcclusionTrackerBase() {}
  30
  31 template <typename LayerType, typename RenderSurfaceType>
  32 void OcclusionTrackerBase<LayerType, RenderSurfaceType>::EnterLayer(
  33     const LayerIteratorPosition<LayerType>& layer_iterator) {
  34   LayerType* render_target = layer_iterator.target_render_surface_layer;
  35
  36   if (layer_iterator.represents_itself)
  37     EnterRenderTarget(render_target);
  38   else if (layer_iterator.represents_target_render_surface)
  39     FinishedRenderTarget(render_target);
  40 }
  41
  42 template <typename LayerType, typename RenderSurfaceType>
  43 void OcclusionTrackerBase<LayerType, RenderSurfaceType>::LeaveLayer(
  44     const LayerIteratorPosition<LayerType>& layer_iterator) {
  45   LayerType* render_target = layer_iterator.target_render_surface_layer;
  46
  47   if (layer_iterator.represents_itself)
  48     MarkOccludedBehindLayer(layer_iterator.current_layer);
  49   // TODO(danakj): This should be done when entering the contributing surface,
  50   // but in a way that the surface's own occlusion won't occlude itself.
  51   else if (layer_iterator.represents_contributing_render_surface)
  52     LeaveToRenderTarget(render_target);
  53 }
  54
  55 template <typename RenderSurfaceType>
  56 static gfx::Rect ScreenSpaceClipRectInTargetSurface(
  57     const RenderSurfaceType* target_surface,
  58     const gfx::Rect& screen_space_clip_rect) {
  59   gfx::Transform inverse_screen_space_transform(
  60       gfx::Transform::kSkipInitialization);
  61   if (!target_surface->screen_space_transform().GetInverse(
  62           &inverse_screen_space_transform))
  63     return target_surface->content_rect();
  64
  65   return MathUtil::ProjectEnclosingClippedRect(inverse_screen_space_transform,
  66                                                screen_space_clip_rect);
  67 }
  68
  69 template <typename RenderSurfaceType>
  70 static Region TransformSurfaceOpaqueRegion(
  71     const Region& region,
  72     bool have_clip_rect,
  73     const gfx::Rect& clip_rect_in_new_target,
  74     const gfx::Transform& transform) {
  75   if (region.IsEmpty())
  76     return Region();
  77
  78   // Verify that rects within the |surface| will remain rects in its target
  79   // surface after applying |transform|. If this is true, then apply |transform|
  80   // to each rect within |region| in order to transform the entire Region.
  81
  82   // TODO(danakj): Find a rect interior to each transformed quad.
  83   if (!transform.Preserves2dAxisAlignment())
  84     return Region();
  85
  86   // TODO(danakj): If the Region is too complex, degrade gracefully here by
  87   // skipping rects in it.
  88   Region transformed_region;
  89   for (Region::Iterator rects(region); rects.has_rect(); rects.next()) {
  90     bool clipped;
  91     gfx::QuadF transformed_quad =
  92         MathUtil::MapQuad(transform, gfx::QuadF(rects.rect()), &clipped);
  93     gfx::Rect transformed_rect =
  94         gfx::ToEnclosedRect(transformed_quad.BoundingBox());
  95     DCHECK(!clipped);  // We only map if the transform preserves axis alignment.
  96     if (have_clip_rect)
  97       transformed_rect.Intersect(clip_rect_in_new_target);
  98     transformed_region.Union(transformed_rect);
  99   }
 100   return transformed_region;
 101 }
 102
 103 static inline bool LayerOpacityKnown(const Layer* layer) {
 104   return !layer->draw_opacity_is_animating();
 105 }
 106 static inline bool LayerOpacityKnown(const LayerImpl* layer) {
 107   return true;
 108 }
 109 static inline bool LayerTransformsToTargetKnown(const Layer* layer) {
 110   return !layer->draw_transform_is_animating();
 111 }
 112 static inline bool LayerTransformsToTargetKnown(const LayerImpl* layer) {
 113   return true;
 114 }
 115
 116 static inline bool SurfaceOpacityKnown(const RenderSurface* rs) {
 117   return !rs->draw_opacity_is_animating();
 118 }
 119 static inline bool SurfaceOpacityKnown(const RenderSurfaceImpl* rs) {
 120   return true;
 121 }
 122 static inline bool SurfaceTransformsToTargetKnown(const RenderSurface* rs) {
 123   return !rs->target_surface_transforms_are_animating();
 124 }
 125 static inline bool SurfaceTransformsToTargetKnown(const RenderSurfaceImpl* rs) {
 126   return true;
 127 }
 128 static inline bool SurfaceTransformsToScreenKnown(const RenderSurface* rs) {
 129   return !rs->screen_space_transforms_are_animating();
 130 }
 131 static inline bool SurfaceTransformsToScreenKnown(const RenderSurfaceImpl* rs) {
 132   return true;
 133 }
 134
 135 static inline bool LayerIsInUnsorted3dRenderingContext(const Layer* layer) {
 136   return layer->is_3d_sorted();
 137 }
 138 static inline bool LayerIsInUnsorted3dRenderingContext(const LayerImpl* layer) {
 139   return false;
 140 }
 141
 142 template <typename LayerType>
 143 static inline bool LayerIsHidden(const LayerType* layer) {
 144   return layer->hide_layer_and_subtree() ||
 145          (layer->parent() && LayerIsHidden(layer->parent()));
 146 }
 147
 148 template <typename LayerType, typename RenderSurfaceType>
 149 void OcclusionTrackerBase<LayerType, RenderSurfaceType>::EnterRenderTarget(
 150     const LayerType* new_target) {
 151   if (!stack_.empty() && stack_.back().target == new_target)
 152     return;
 153
 154   const LayerType* old_target = NULL;
 155   const RenderSurfaceType* old_occlusion_immune_ancestor = NULL;
 156   if (!stack_.empty()) {
 157     old_target = stack_.back().target;
 158     old_occlusion_immune_ancestor =
 159         old_target->render_surface()->nearest_occlusion_immune_ancestor();
 160   }
 161   const RenderSurfaceType* new_occlusion_immune_ancestor =
 162       new_target->render_surface()->nearest_occlusion_immune_ancestor();
 163
 164   stack_.push_back(StackObject(new_target));
 165
 166   // We copy the screen occlusion into the new RenderSurface subtree, but we
 167   // never copy in the occlusion from inside the target, since we are looking
 168   // at a new RenderSurface target.
 169
 170   // If entering an unoccluded subtree, do not carry forward the outside
 171   // occlusion calculated so far.
 172   bool entering_unoccluded_subtree =
 173       new_occlusion_immune_ancestor &&
 174       new_occlusion_immune_ancestor != old_occlusion_immune_ancestor;
 175
 176   bool have_transform_from_screen_to_new_target = false;
 177   gfx::Transform inverse_new_target_screen_space_transform(
 178       // Note carefully, not used if screen space transform is uninvertible.
 179       gfx::Transform::kSkipInitialization);
 180   if (SurfaceTransformsToScreenKnown(new_target->render_surface())) {
 181     have_transform_from_screen_to_new_target =
 182         new_target->render_surface()->screen_space_transform().GetInverse(
 183             &inverse_new_target_screen_space_transform);
 184   }
 185
 186   bool entering_root_target = new_target->parent() == NULL;
 187
 188   bool copy_outside_occlusion_forward =
 189       stack_.size() > 1 &&
 190       !entering_unoccluded_subtree &&
 191       have_transform_from_screen_to_new_target &&
 192       !entering_root_target;
 193   if (!copy_outside_occlusion_forward)
 194     return;
 195
 196   int last_index = stack_.size() - 1;
 197   gfx::Transform old_target_to_new_target_transform(
 198       inverse_new_target_screen_space_transform,
 199       old_target->render_surface()->screen_space_transform());
 200   stack_[last_index].occlusion_from_outside_target =
 201       TransformSurfaceOpaqueRegion<RenderSurfaceType>(
 202           stack_[last_index - 1].occlusion_from_outside_target,
 203           false,
 204           gfx::Rect(),
 205           old_target_to_new_target_transform);
 206   stack_[last_index].occlusion_from_outside_target.Union(
 207       TransformSurfaceOpaqueRegion<RenderSurfaceType>(
 208           stack_[last_index - 1].occlusion_from_inside_target,
 209           false,
 210           gfx::Rect(),
 211           old_target_to_new_target_transform));
 212 }
 213
 214 template <typename LayerType, typename RenderSurfaceType>
 215 void OcclusionTrackerBase<LayerType, RenderSurfaceType>::FinishedRenderTarget(
 216     const LayerType* finished_target) {
 217   // Make sure we know about the target surface.
 218   EnterRenderTarget(finished_target);
 219
 220   RenderSurfaceType* surface = finished_target->render_surface();
 221
 222   // Readbacks always happen on render targets so we only need to check
 223   // for readbacks here.
 224   bool target_is_only_for_copy_request =
 225       finished_target->HasCopyRequest() && LayerIsHidden(finished_target);
 226
 227   // If the occlusion within the surface can not be applied to things outside of
 228   // the surface's subtree, then clear the occlusion here so it won't be used.
 229   if (finished_target->mask_layer() || !SurfaceOpacityKnown(surface) ||
 230       surface->draw_opacity() < 1 ||
 231       !finished_target->uses_default_blend_mode() ||
 232       target_is_only_for_copy_request ||
 233       finished_target->filters().HasFilterThatAffectsOpacity()) {
 234     stack_.back().occlusion_from_outside_target.Clear();
 235     stack_.back().occlusion_from_inside_target.Clear();
 236   } else if (!SurfaceTransformsToTargetKnown(surface)) {
 237     stack_.back().occlusion_from_inside_target.Clear();
 238     stack_.back().occlusion_from_outside_target.Clear();
 239   }
 240 }
 241
 242 template <typename LayerType>
 243 static void ReduceOcclusionBelowSurface(LayerType* contributing_layer,
 244                                         const gfx::Rect& surface_rect,
 245                                         const gfx::Transform& surface_transform,
 246                                         LayerType* render_target,
 247                                         Region* occlusion_from_inside_target) {
 248   if (surface_rect.IsEmpty())
 249     return;
 250
 251   gfx::Rect affected_area_in_target =
 252       MathUtil::MapEnclosingClippedRect(surface_transform, surface_rect);
 253   if (contributing_layer->render_surface()->is_clipped()) {
 254     affected_area_in_target.Intersect(
 255         contributing_layer->render_surface()->clip_rect());
 256   }
 257   if (affected_area_in_target.IsEmpty())
 258     return;
 259
 260   int outset_top, outset_right, outset_bottom, outset_left;
 261   contributing_layer->background_filters().GetOutsets(
 262       &outset_top, &outset_right, &outset_bottom, &outset_left);
 263
 264   // The filter can move pixels from outside of the clip, so allow affected_area
 265   // to expand outside the clip.
 266   affected_area_in_target.Inset(
 267       -outset_left, -outset_top, -outset_right, -outset_bottom);
 268   Region affected_occlusion = IntersectRegions(*occlusion_from_inside_target,
 269                                                affected_area_in_target);
 270   Region::Iterator affected_occlusion_rects(affected_occlusion);
 271
 272   occlusion_from_inside_target->Subtract(affected_area_in_target);
 273   for (; affected_occlusion_rects.has_rect(); affected_occlusion_rects.next()) {
 274     gfx::Rect occlusion_rect = affected_occlusion_rects.rect();
 275
 276     // Shrink the rect by expanding the non-opaque pixels outside the rect.
 277
 278     // The left outset of the filters moves pixels on the right side of
 279     // the occlusion_rect into it, shrinking its right edge.
 280     int shrink_left =
 281         occlusion_rect.x() == affected_area_in_target.x() ? 0 : outset_right;
 282     int shrink_top =
 283         occlusion_rect.y() == affected_area_in_target.y() ? 0 : outset_bottom;
 284     int shrink_right =
 285         occlusion_rect.right() == affected_area_in_target.right() ?
 286         0 : outset_left;
 287     int shrink_bottom =
 288         occlusion_rect.bottom() == affected_area_in_target.bottom() ?
 289         0 : outset_top;
 290
 291     occlusion_rect.Inset(shrink_left, shrink_top, shrink_right, shrink_bottom);
 292
 293     occlusion_from_inside_target->Union(occlusion_rect);
 294   }
 295 }
 296
 297 template <typename LayerType, typename RenderSurfaceType>
 298 void OcclusionTrackerBase<LayerType, RenderSurfaceType>::LeaveToRenderTarget(
 299     const LayerType* new_target) {
 300   int last_index = stack_.size() - 1;
 301   bool surface_will_be_at_top_after_pop =
 302       stack_.size() > 1 && stack_[last_index - 1].target == new_target;
 303
 304   // We merge the screen occlusion from the current RenderSurfaceImpl subtree
 305   // out to its parent target RenderSurfaceImpl. The target occlusion can be
 306   // merged out as well but needs to be transformed to the new target.
 307
 308   const LayerType* old_target = stack_[last_index].target;
 309   const RenderSurfaceType* old_surface = old_target->render_surface();
 310
 311   Region old_occlusion_from_inside_target_in_new_target =
 312       TransformSurfaceOpaqueRegion<RenderSurfaceType>(
 313           stack_[last_index].occlusion_from_inside_target,
 314           old_surface->is_clipped(),
 315           old_surface->clip_rect(),
 316           old_surface->draw_transform());
 317   if (old_target->has_replica() && !old_target->replica_has_mask()) {
 318     old_occlusion_from_inside_target_in_new_target.Union(
 319         TransformSurfaceOpaqueRegion<RenderSurfaceType>(
 320             stack_[last_index].occlusion_from_inside_target,
 321             old_surface->is_clipped(),
 322             old_surface->clip_rect(),
 323             old_surface->replica_draw_transform()));
 324   }
 325
 326   Region old_occlusion_from_outside_target_in_new_target =
 327       TransformSurfaceOpaqueRegion<RenderSurfaceType>(
 328           stack_[last_index].occlusion_from_outside_target,
 329           false,
 330           gfx::Rect(),
 331           old_surface->draw_transform());
 332
 333   gfx::Rect unoccluded_surface_rect;
 334   gfx::Rect unoccluded_replica_rect;
 335   if (old_target->background_filters().HasFilterThatMovesPixels()) {
 336     unoccluded_surface_rect = UnoccludedContributingSurfaceContentRect(
 337         old_target, false, old_surface->content_rect());
 338     if (old_target->has_replica()) {
 339       unoccluded_replica_rect = UnoccludedContributingSurfaceContentRect(
 340           old_target, true, old_surface->content_rect());
 341     }
 342   }
 343
 344   if (surface_will_be_at_top_after_pop) {
 345     // Merge the top of the stack down.
 346     stack_[last_index - 1].occlusion_from_inside_target.Union(
 347         old_occlusion_from_inside_target_in_new_target);
 348     // TODO(danakj): Strictly this should subtract the inside target occlusion
 349     // before union.
 350     if (new_target->parent()) {
 351       stack_[last_index - 1].occlusion_from_outside_target.Union(
 352           old_occlusion_from_outside_target_in_new_target);
 353     }
 354     stack_.pop_back();
 355   } else {
 356     // Replace the top of the stack with the new pushed surface.
 357     stack_.back().target = new_target;
 358     stack_.back().occlusion_from_inside_target =
 359         old_occlusion_from_inside_target_in_new_target;
 360     if (new_target->parent()) {
 361       stack_.back().occlusion_from_outside_target =
 362           old_occlusion_from_outside_target_in_new_target;
 363     } else {
 364       stack_.back().occlusion_from_outside_target.Clear();
 365     }
 366   }
 367
 368   if (!old_target->background_filters().HasFilterThatMovesPixels())
 369     return;
 370
 371   ReduceOcclusionBelowSurface(old_target,
 372                               unoccluded_surface_rect,
 373                               old_surface->draw_transform(),
 374                               new_target,
 375                               &stack_.back().occlusion_from_inside_target);
 376   ReduceOcclusionBelowSurface(old_target,
 377                               unoccluded_surface_rect,
 378                               old_surface->draw_transform(),
 379                               new_target,
 380                               &stack_.back().occlusion_from_outside_target);
 381
 382   if (!old_target->has_replica())
 383     return;
 384   ReduceOcclusionBelowSurface(old_target,
 385                               unoccluded_replica_rect,
 386                               old_surface->replica_draw_transform(),
 387                               new_target,
 388                               &stack_.back().occlusion_from_inside_target);
 389   ReduceOcclusionBelowSurface(old_target,
 390                               unoccluded_replica_rect,
 391                               old_surface->replica_draw_transform(),
 392                               new_target,
 393                               &stack_.back().occlusion_from_outside_target);
 394 }
 395
 396 template <typename LayerType, typename RenderSurfaceType>
 397 void OcclusionTrackerBase<LayerType, RenderSurfaceType>::
 398     MarkOccludedBehindLayer(const LayerType* layer) {
 399   DCHECK(!stack_.empty());
 400   DCHECK_EQ(layer->render_target(), stack_.back().target);
 401   if (stack_.empty())
 402     return;
 403
 404   if (!layer->DrawsContent())
 405     return;
 406
 407   if (!LayerOpacityKnown(layer) || layer->draw_opacity() < 1)
 408     return;
 409
 410   if (!layer->uses_default_blend_mode())
 411     return;
 412
 413   if (LayerIsInUnsorted3dRenderingContext(layer))
 414     return;
 415
 416   if (!LayerTransformsToTargetKnown(layer))
 417     return;
 418
 419   Region opaque_contents = layer->VisibleContentOpaqueRegion();
 420   if (opaque_contents.IsEmpty())
 421     return;
 422
 423   DCHECK(layer->visible_content_rect().Contains(opaque_contents.bounds()));
 424
 425   // TODO(danakj): Find a rect interior to each transformed quad.
 426   if (!layer->draw_transform().Preserves2dAxisAlignment())
 427     return;
 428
 429   gfx::Rect clip_rect_in_target = ScreenSpaceClipRectInTargetSurface(
 430       layer->render_target()->render_surface(), screen_space_clip_rect_);
 431   if (layer->is_clipped()) {
 432     clip_rect_in_target.Intersect(layer->clip_rect());
 433   } else {
 434     clip_rect_in_target.Intersect(
 435         layer->render_target()->render_surface()->content_rect());
 436   }
 437
 438   for (Region::Iterator opaque_content_rects(opaque_contents);
 439        opaque_content_rects.has_rect();
 440        opaque_content_rects.next()) {
 441     bool clipped;
 442     gfx::QuadF transformed_quad = MathUtil::MapQuad(
 443         layer->draw_transform(),
 444         gfx::QuadF(opaque_content_rects.rect()),
 445         &clipped);
 446     gfx::Rect transformed_rect =
 447         gfx::ToEnclosedRect(transformed_quad.BoundingBox());
 448     DCHECK(!clipped);  // We only map if the transform preserves axis alignment.
 449     transformed_rect.Intersect(clip_rect_in_target);
 450     if (transformed_rect.width() < minimum_tracking_size_.width() &&
 451         transformed_rect.height() < minimum_tracking_size_.height())
 452       continue;
 453     stack_.back().occlusion_from_inside_target.Union(transformed_rect);
 454
 455     if (!occluding_screen_space_rects_)
 456       continue;
 457
 458     // Save the occluding area in screen space for debug visualization.
 459     gfx::QuadF screen_space_quad = MathUtil::MapQuad(
 460         layer->render_target()->render_surface()->screen_space_transform(),
 461         gfx::QuadF(transformed_rect), &clipped);
 462     // TODO(danakj): Store the quad in the debug info instead of the bounding
 463     // box.
 464     gfx::Rect screen_space_rect =
 465         gfx::ToEnclosedRect(screen_space_quad.BoundingBox());
 466     occluding_screen_space_rects_->push_back(screen_space_rect);
 467   }
 468
 469   if (!non_occluding_screen_space_rects_)
 470     return;
 471
 472   Region non_opaque_contents =
 473       SubtractRegions(gfx::Rect(layer->content_bounds()), opaque_contents);
 474   for (Region::Iterator non_opaque_content_rects(non_opaque_contents);
 475        non_opaque_content_rects.has_rect();
 476        non_opaque_content_rects.next()) {
 477     // We've already checked for clipping in the MapQuad call above, these calls
 478     // should not clip anything further.
 479     gfx::Rect transformed_rect = gfx::ToEnclosedRect(
 480         MathUtil::MapClippedRect(layer->draw_transform(),
 481                                  gfx::RectF(non_opaque_content_rects.rect())));
 482     transformed_rect.Intersect(clip_rect_in_target);
 483     if (transformed_rect.IsEmpty())
 484       continue;
 485
 486     bool clipped;
 487     gfx::QuadF screen_space_quad = MathUtil::MapQuad(
 488         layer->render_target()->render_surface()->screen_space_transform(),
 489         gfx::QuadF(transformed_rect),
 490         &clipped);
 491     // TODO(danakj): Store the quad in the debug info instead of the bounding
 492     // box.
 493     gfx::Rect screen_space_rect =
 494         gfx::ToEnclosedRect(screen_space_quad.BoundingBox());
 495     non_occluding_screen_space_rects_->push_back(screen_space_rect);
 496   }
 497 }
 498
 499 template <typename LayerType, typename RenderSurfaceType>
 500 bool OcclusionTrackerBase<LayerType, RenderSurfaceType>::Occluded(
 501     const LayerType* render_target,
 502     const gfx::Rect& content_rect,
 503     const gfx::Transform& draw_transform,
 504     bool impl_draw_transform_is_unknown) const {
 505   DCHECK(!stack_.empty());
 506   if (stack_.empty())
 507     return false;
 508   if (content_rect.IsEmpty())
 509     return true;
 510   if (impl_draw_transform_is_unknown)
 511     return false;
 512
 513   // For tests with no render target.
 514   if (!render_target)
 515     return false;
 516
 517   DCHECK_EQ(render_target->render_target(), render_target);
 518   DCHECK(render_target->render_surface());
 519   DCHECK_EQ(render_target, stack_.back().target);
 520
 521   if (stack_.back().occlusion_from_inside_target.IsEmpty() &&
 522       stack_.back().occlusion_from_outside_target.IsEmpty()) {
 523     return false;
 524   }
 525
 526   gfx::Transform inverse_draw_transform(gfx::Transform::kSkipInitialization);
 527   if (!draw_transform.GetInverse(&inverse_draw_transform))
 528     return false;
 529
 530   // Take the ToEnclosingRect at each step, as we want to contain any unoccluded
 531   // partial pixels in the resulting Rect.
 532   Region unoccluded_region_in_target_surface =
 533       MathUtil::MapEnclosingClippedRect(draw_transform, content_rect);
 534   unoccluded_region_in_target_surface.Subtract(
 535       stack_.back().occlusion_from_inside_target);
 536   gfx::RectF unoccluded_rect_in_target_surface_without_outside_occlusion =
 537       unoccluded_region_in_target_surface.bounds();
 538   unoccluded_region_in_target_surface.Subtract(
 539       stack_.back().occlusion_from_outside_target);
 540
 541   gfx::RectF unoccluded_rect_in_target_surface =
 542       unoccluded_region_in_target_surface.bounds();
 543
 544   return unoccluded_rect_in_target_surface.IsEmpty();
 545 }
 546
 547 template <typename LayerType, typename RenderSurfaceType>
 548 gfx::Rect OcclusionTrackerBase<LayerType, RenderSurfaceType>::
 549     UnoccludedContentRect(
 550         const LayerType* render_target,
 551         const gfx::Rect& content_rect,
 552         const gfx::Transform& draw_transform,
 553         bool impl_draw_transform_is_unknown) const {
 554   DCHECK(!stack_.empty());
 555   if (stack_.empty())
 556     return content_rect;
 557   if (content_rect.IsEmpty())
 558     return content_rect;
 559   if (impl_draw_transform_is_unknown)
 560     return content_rect;
 561
 562   // For tests with no render target.
 563   if (!render_target)
 564     return content_rect;
 565
 566   DCHECK_EQ(render_target->render_target(), render_target);
 567   DCHECK(render_target->render_surface());
 568   DCHECK_EQ(render_target, stack_.back().target);
 569
 570   if (stack_.back().occlusion_from_inside_target.IsEmpty() &&
 571       stack_.back().occlusion_from_outside_target.IsEmpty()) {
 572     return content_rect;
 573   }
 574
 575   gfx::Transform inverse_draw_transform(gfx::Transform::kSkipInitialization);
 576   if (!draw_transform.GetInverse(&inverse_draw_transform))
 577     return content_rect;
 578
 579   // Take the ToEnclosingRect at each step, as we want to contain any unoccluded
 580   // partial pixels in the resulting Rect.
 581   Region unoccluded_region_in_target_surface =
 582       MathUtil::MapEnclosingClippedRect(draw_transform, content_rect);
 583   unoccluded_region_in_target_surface.Subtract(
 584       stack_.back().occlusion_from_inside_target);
 585   unoccluded_region_in_target_surface.Subtract(
 586       stack_.back().occlusion_from_outside_target);
 587
 588   gfx::Rect unoccluded_rect_in_target_surface =
 589       unoccluded_region_in_target_surface.bounds();
 590   gfx::Rect unoccluded_rect = MathUtil::ProjectEnclosingClippedRect(
 591       inverse_draw_transform, unoccluded_rect_in_target_surface);
 592   unoccluded_rect.Intersect(content_rect);
 593
 594   return unoccluded_rect;
 595 }
 596
 597 template <typename LayerType, typename RenderSurfaceType>
 598 gfx::Rect OcclusionTrackerBase<LayerType, RenderSurfaceType>::
 599     UnoccludedContributingSurfaceContentRect(
 600         const LayerType* layer,
 601         bool for_replica,
 602         const gfx::Rect& content_rect) const {
 603   DCHECK(!stack_.empty());
 604   // The layer is a contributing render_target so it should have a surface.
 605   DCHECK(layer->render_surface());
 606   // The layer is a contributing render_target so its target should be itself.
 607   DCHECK_EQ(layer->render_target(), layer);
 608   // The layer should not be the root, else what is is contributing to?
 609   DCHECK(layer->parent());
 610   // This should be called while the layer is still considered the current
 611   // target in the occlusion tracker.
 612   DCHECK_EQ(layer, stack_.back().target);
 613
 614   if (content_rect.IsEmpty())
 615     return content_rect;
 616
 617   const RenderSurfaceType* surface = layer->render_surface();
 618   const LayerType* contributing_surface_render_target =
 619       layer->parent()->render_target();
 620
 621   if (!SurfaceTransformsToTargetKnown(surface))
 622     return content_rect;
 623
 624   gfx::Transform draw_transform =
 625       for_replica ? surface->replica_draw_transform()
 626                   : surface->draw_transform();
 627   gfx::Transform inverse_draw_transform(gfx::Transform::kSkipInitialization);
 628   if (!draw_transform.GetInverse(&inverse_draw_transform))
 629     return content_rect;
 630
 631   // A contributing surface doesn't get occluded by things inside its own
 632   // surface, so only things outside the surface can occlude it. That occlusion
 633   // is found just below the top of the stack (if it exists).
 634   bool has_occlusion = stack_.size() > 1;
 635
 636   // Take the ToEnclosingRect at each step, as we want to contain any unoccluded
 637   // partial pixels in the resulting Rect.
 638   Region unoccluded_region_in_target_surface =
 639       MathUtil::MapEnclosingClippedRect(draw_transform, content_rect);
 640   // Layers can't clip across surfaces, so count this as internal occlusion.
 641   if (surface->is_clipped())
 642     unoccluded_region_in_target_surface.Intersect(surface->clip_rect());
 643   if (has_occlusion) {
 644     const StackObject& second_last = stack_[stack_.size() - 2];
 645     unoccluded_region_in_target_surface.Subtract(
 646         second_last.occlusion_from_inside_target);
 647     unoccluded_region_in_target_surface.Subtract(
 648         second_last.occlusion_from_outside_target);
 649   }
 650
 651   // Treat other clipping as occlusion from outside the target surface.
 652   unoccluded_region_in_target_surface.Intersect(
 653       contributing_surface_render_target->render_surface()->content_rect());
 654   unoccluded_region_in_target_surface.Intersect(
 655       ScreenSpaceClipRectInTargetSurface(
 656           contributing_surface_render_target->render_surface(),
 657           screen_space_clip_rect_));
 658
 659   gfx::Rect unoccluded_rect_in_target_surface =
 660       unoccluded_region_in_target_surface.bounds();
 661   gfx::Rect unoccluded_rect = MathUtil::ProjectEnclosingClippedRect(
 662       inverse_draw_transform, unoccluded_rect_in_target_surface);
 663   unoccluded_rect.Intersect(content_rect);
 664
 665   return unoccluded_rect;
 666 }
 667
 668 // Instantiate (and export) templates here for the linker.
 669 template class OcclusionTrackerBase<Layer, RenderSurface>;
 670 template class OcclusionTrackerBase<LayerImpl, RenderSurfaceImpl>;
 671
 672 }  // namespace cc