cc: Enable non-opaque harware overlays.

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/buffer_types.h"
 #include "ui/gfx/geometry/rect_conversions.h"
 
 namespace cc {
+namespace {
+
+const gfx::BufferFormat kOverlayFormatsWithAlpha[] = {
+    gfx::BufferFormat::RGBA_8888, gfx::BufferFormat::BGRA_8888};
+}
 
 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) &&
         // TODO(dcastagna): Remove this once drm platform supports transforms.
         candidate.transform == gfx::OVERLAY_TRANSFORM_NONE &&
         !OverlayCandidate::IsOccluded(candidate, quad_list->cbegin(), it)) {
+      // We currently reject quads with alpha that do not request alpha blending
+      // since the alpha channel might not be set to 1 and we're not disabling
+      // blending when scanning out.
+      // TODO(dcastagna): We should support alpha formats without blending using
+      // the opaque FB at scanout.
+      if (std::find(std::begin(kOverlayFormatsWithAlpha),
+                    std::end(kOverlayFormatsWithAlpha),
+                    candidate.format) != std::end(kOverlayFormatsWithAlpha) &&
+          it->shared_quad_state->blend_mode == SkBlendMode::kSrc)
+        continue;
+
       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;
 
@@ skipping 21 matching lines @@
   if (overlay_candidate.overlay_handled) {
     quad_list->EraseAndInvalidateAllPointers(candidate_iterator);
     candidate_list->swap(new_candidate_list);
     return true;
   }
 
   return false;
 }
 
 }  // namespace cc