Let OverlayStrategySingleOnTop select non-topmost quad

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/quads/draw_quad.h"
 #include "cc/quads/texture_draw_quad.h"
 #include "ui/gfx/geometry/rect_conversions.h"
 #include "ui/gfx/transform.h"
@@ skipping 10 matching lines @@
     RenderPassList* render_passes_in_draw_order,
     OverlayCandidateList* candidate_list) {
   // Only attempt to handle very simple case for now.
   if (!capability_checker_)
     return false;
 
   RenderPass* root_render_pass = render_passes_in_draw_order->back();
   DCHECK(root_render_pass);
 
   QuadList& quad_list = root_render_pass->quad_list;
-  const DrawQuad* candidate_quad = quad_list.front();
-  if (candidate_quad->material != DrawQuad::TEXTURE_CONTENT)
+  QuadList::iterator candidate_iterator = quad_list.end();
+  for (QuadList::iterator it = quad_list.begin(); it != quad_list.end(); ++it) {
+    const DrawQuad* draw_quad = *it;
+    if (draw_quad->material == DrawQuad::TEXTURE_CONTENT) {
+      const TextureDrawQuad& quad = *TextureDrawQuad::MaterialCast(draw_quad);
+      if (!resource_provider_->AllowOverlay(quad.resource_id)) {
+        continue;
+      }
+      // Check that no prior quads overlap it.
+      bool intersects = false;
+      gfx::RectF rect = draw_quad->rect;
+      draw_quad->quadTransform().TransformRect(&rect);
+      for (QuadList::iterator overlap_iter = quad_list.begin();
+           overlap_iter != it;
+           ++overlap_iter) {
+        gfx::RectF overlap_rect = (*overlap_iter)->rect;
+        (*overlap_iter)->quadTransform().TransformRect(&overlap_rect);
+        if (rect.Intersects(overlap_rect)) {
+          intersects = true;
+          break;
+        }
+      }
+      if (intersects)
+        continue;
+      candidate_iterator = it;
+      break;
+    }
+  }
+  if (candidate_iterator == quad_list.end())
     return false;
-
-  const TextureDrawQuad& quad = *TextureDrawQuad::MaterialCast(candidate_quad);
-  if (!resource_provider_->AllowOverlay(quad.resource_id))
-    return false;
+  const TextureDrawQuad& quad =
+      *TextureDrawQuad::MaterialCast(*candidate_iterator);
 
   // Simple quads only.
   gfx::OverlayTransform overlay_transform =
       OverlayCandidate::GetOverlayTransform(quad.quadTransform(), quad.flipped);
   if (overlay_transform == gfx::OVERLAY_TRANSFORM_INVALID ||
-      !quad.quadTransform().IsIdentityOrTranslation() || quad.needs_blending ||
-      quad.shared_quad_state->opacity != 1.f ||
+      quad.needs_blending || quad.shared_quad_state->opacity != 1.f ||
       quad.shared_quad_state->blend_mode != SkXfermode::kSrcOver_Mode ||
-      quad.premultiplied_alpha || quad.background_color != SK_ColorTRANSPARENT)
+      quad.background_color != SK_ColorTRANSPARENT)
     return false;
 
   // Add our primary surface.
   OverlayCandidateList candidates;
   OverlayCandidate main_image;
   main_image.display_rect = root_render_pass->output_rect;
   main_image.format = RGBA_8888;
   candidates.push_back(main_image);
 
   // Add the overlay.
   OverlayCandidate candidate;
   candidate.transform = overlay_transform;
   candidate.display_rect =
       OverlayCandidate::GetOverlayRect(quad.quadTransform(), quad.rect);
   candidate.uv_rect = BoundingRect(quad.uv_top_left, quad.uv_bottom_right);
   candidate.format = RGBA_8888;
   candidate.resource_id = quad.resource_id;
   candidate.plane_z_order = 1;
   candidates.push_back(candidate);
 
   // Check for support.
   capability_checker_->CheckOverlaySupport(&candidates);
 
   // If the candidate can be handled by an overlay, create a pass for it.
   if (candidates[1].overlay_handled) {
-    scoped_ptr<DrawQuad> overlay_quad = quad_list.take(quad_list.begin());
-    quad_list.erase(quad_list.begin());
+    quad_list.erase(candidate_iterator);
     candidate_list->swap(candidates);
     return true;
   }
   return false;
 }
 
 }  // namespace cc