cc: Pick the biggest Quad when selecting an overlay.

cc/output/overlay_strategy_single_on_top.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/output/overlay_strategy_single_on_top.h"
 
 #include "cc/base/math_util.h"
 #include "cc/output/overlay_candidate_validator.h"
 #include "cc/quads/draw_quad.h"
 #include "ui/gfx/geometry/rect_conversions.h"
 
 namespace cc {
 
 OverlayStrategySingleOnTop::OverlayStrategySingleOnTop(
     OverlayCandidateValidator* capability_checker)
     : capability_checker_(capability_checker) {
   DCHECK(capability_checker);
 }
 
 OverlayStrategySingleOnTop::~OverlayStrategySingleOnTop() {}
 
 bool OverlayStrategySingleOnTop::Attempt(
     ResourceProvider* resource_provider,
     RenderPass* render_pass,
     OverlayCandidateList* candidate_list,
     std::vector<gfx::Rect>* content_bounds) {
   QuadList* quad_list = &render_pass->quad_list;
+  // Build a list of candidates with the associated quad.
+  OverlayCandidate best_candidate;
+  QuadList::Iterator best_quad_it = quad_list->end();
   for (auto it = quad_list->begin(); it != quad_list->end(); ++it) {
     OverlayCandidate candidate;
     if (OverlayCandidate::FromDrawQuad(resource_provider, *it, &candidate) &&
-        TryOverlay(quad_list, candidate_list, candidate, it)) {
-      return true;
+        // TODO(dcastagna): Remove this once drm platform supports transforms.
+        candidate.transform == gfx::OVERLAY_TRANSFORM_NONE &&
+        !OverlayCandidate::IsOccluded(candidate, quad_list->cbegin(), it)) {
+      if (candidate.display_rect.size().GetArea() >
+          best_candidate.display_rect.size().GetArea()) {
+        best_candidate = candidate;
+        best_quad_it = it;
+      }
     }
   }
+  if (best_quad_it == quad_list->end())
+    return false;
+
+  if (TryOverlay(quad_list, candidate_list, best_candidate, best_quad_it))
+    return true;
 
   return false;
 }
 
 bool OverlayStrategySingleOnTop::TryOverlay(
     QuadList* quad_list,
     OverlayCandidateList* candidate_list,
     const OverlayCandidate& candidate,
     QuadList::Iterator candidate_iterator) {
-  // Reject transformed overlays.
-  // TODO(dcastagna): Remove this once drm platform supports transforms.
-  if (candidate.transform != gfx::OVERLAY_TRANSFORM_NONE)
-    return false;
-  // Check that no prior quads overlap it.
-  if (OverlayCandidate::IsOccluded(candidate, quad_list->cbegin(),
-                                   candidate_iterator))
-    return false;
-
   // Add the overlay.
   OverlayCandidateList new_candidate_list = *candidate_list;
   new_candidate_list.push_back(candidate);
   new_candidate_list.back().plane_z_order = 1;
 
   // Check for support.
   capability_checker_->CheckOverlaySupport(&new_candidate_list);
 
   const OverlayCandidate& overlay_candidate = new_candidate_list.back();
   // If the candidate can be handled by an overlay, create a pass for it.
   if (overlay_candidate.overlay_handled) {
     quad_list->EraseAndInvalidateAllPointers(candidate_iterator);
     candidate_list->swap(new_candidate_list);
     return true;
   }
 
   return false;
 }
 
 }  // namespace cc