Mac Overlays: Allow multiple overlays with sandwich strategy

cc/output/overlay_strategy_sandwich.cc

 // Copyright 2015 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_sandwich.h"
 
 #include "cc/base/region.h"
 #include "cc/output/overlay_candidate_validator.h"
 #include "cc/quads/draw_quad.h"
 #include "cc/quads/solid_color_draw_quad.h"
@@ skipping 13 matching lines @@
 bool IsPixelRectAlignedToDIP(float scale_factor, const gfx::Rect& pixel_rect) {
   return (pixel_rect == AlignPixelRectToDIP(scale_factor, pixel_rect));
 }
 
 }  // namespace
 
 namespace cc {
 
 OverlayStrategySandwich::~OverlayStrategySandwich() {}
 
-bool OverlayStrategySandwich::TryOverlay(
+QuadList::Iterator OverlayStrategySandwich::TryOverlay(
     OverlayCandidateValidator* capability_checker,
     RenderPassList* render_passes_in_draw_order,
     OverlayCandidateList* output_candidate_list,
     const OverlayCandidate& candidate,
     QuadList::Iterator candidate_iter_in_quad_list,
     float device_scale_factor) {
   RenderPass* root_render_pass = render_passes_in_draw_order->back();
   QuadList& quad_list = root_render_pass->quad_list;
   gfx::Rect pixel_bounds = root_render_pass->output_rect;
 
   const DrawQuad* candidate_quad = *candidate_iter_in_quad_list;
   const gfx::Transform& candidate_transform =
       candidate_quad->shared_quad_state->quad_to_target_transform;
   gfx::Transform candidate_inverse_transform;
   if (!candidate_transform.GetInverse(&candidate_inverse_transform))
-    return false;
+    return ++candidate_iter_in_quad_list;
 
   // Compute the candidate's rect in display space (pixels on the screen). The
   // rect needs to be DIP-aligned, or we cannot use it.
   gfx::RectF candidate_pixel_rect_float = candidate_quad->rect;
   candidate_transform.TransformRect(&candidate_pixel_rect_float);
-  gfx::Rect candidate_pixel_rect;
-  candidate_pixel_rect = gfx::ToEnclosingRect(candidate_pixel_rect_float);
-  if (candidate_pixel_rect != candidate_pixel_rect_float)
-    return false;
-  if (!IsPixelRectAlignedToDIP(device_scale_factor, candidate_pixel_rect))
-    return false;
+  const gfx::Rect candidate_pixel_rect =
+      gfx::ToEnclosingRect(candidate_pixel_rect_float);
+  if (candidate_pixel_rect != candidate_pixel_rect_float ||
+      !IsPixelRectAlignedToDIP(device_scale_factor, candidate_pixel_rect)) {
+    return ++candidate_iter_in_quad_list;
+  }
 
-  // Iterate through the quads in front of |potential_candidate|, and compute
-  // the region of |potential_candidate| that is covered.
+  // Iterate through the quads in front of |candidate|, and compute the region
+  // of |candidate| that is covered.
   Region pixel_covered_region;
   for (auto overlap_iter = quad_list.cbegin();
        overlap_iter != candidate_iter_in_quad_list; ++overlap_iter) {
     if (OverlayStrategyCommon::IsInvisibleQuad(*overlap_iter))
       continue;
     // Compute the quad's bounds in display space, and ensure that it is rounded
     // up to be DIP-aligned.
     gfx::RectF pixel_covered_rect_float = overlap_iter->rect;
     overlap_iter->shared_quad_state->quad_to_target_transform.TransformRect(
         &pixel_covered_rect_float);
     gfx::Rect pixel_covered_rect = AlignPixelRectToDIP(
         device_scale_factor, gfx::ToEnclosingRect(pixel_covered_rect_float));
 
     // Include the intersection of that quad with the candidate's quad in the
     // covered region.
     pixel_covered_rect.Intersect(candidate_pixel_rect);
     pixel_covered_region.Union(pixel_covered_rect);

[ccameron, 2015/09/02 21:41:55]

We should only promote to an overlay layer here if we don't intersect any of the
existing candidates.

[Andre, 2015/09/02 21:54:51]

Got it.

   }
 
-  // Add our primary surface.
-  OverlayCandidateList new_candidate_list;
-  OverlayCandidate main_image;
-  main_image.display_rect = pixel_bounds;
-  new_candidate_list.push_back(main_image);
-
   // Add the candidate's overlay.
   DCHECK(candidate.resource_id);
+  OverlayCandidateList new_candidate_list;
   new_candidate_list.push_back(candidate);
   new_candidate_list.back().plane_z_order = 1;
 
   // Add an overlay of the primary surface for any part of the candidate's
   // quad that was covered.
   std::vector<gfx::Rect> pixel_covered_rects;
   for (Region::Iterator it(pixel_covered_region); it.has_rect(); it.next()) {
     DCHECK(IsPixelRectAlignedToDIP(device_scale_factor, it.rect()));
     pixel_covered_rects.push_back(it.rect());
   }
   for (const gfx::Rect& pixel_covered_rect : pixel_covered_rects) {
     OverlayCandidate main_image_on_top;
     main_image_on_top.display_rect = pixel_covered_rect;
     main_image_on_top.uv_rect = pixel_covered_rect;
     main_image_on_top.uv_rect.Scale(1.f / pixel_bounds.width(),
                                     1.f / pixel_bounds.height());
     main_image_on_top.plane_z_order = 2;
     main_image_on_top.transform = gfx::OVERLAY_TRANSFORM_NONE;
     main_image_on_top.use_output_surface_for_resource = true;
     new_candidate_list.push_back(main_image_on_top);
   }
 
   // Check for support.
   capability_checker->CheckOverlaySupport(&new_candidate_list);
   for (const OverlayCandidate& candidate : new_candidate_list) {
-    if (candidate.plane_z_order > 0 && !candidate.overlay_handled)
-      return false;
+    if (!candidate.overlay_handled)
+      return ++candidate_iter_in_quad_list;
   }
 
   // Remove the quad for the overlay quad. Replace it with a transparent quad
   // if we're putting a new overlay on top.
   if (pixel_covered_rects.empty()) {
-    quad_list.EraseAndInvalidateAllPointers(candidate_iter_in_quad_list);
+    candidate_iter_in_quad_list =
+        quad_list.EraseAndInvalidateAllPointers(candidate_iter_in_quad_list);
   } else {
     // Cache the information from the candidate quad that we'll need to
     // construct the solid color quads.
     const SharedQuadState* candidate_shared_quad_state =
         candidate_quad->shared_quad_state;
     const gfx::Rect candidate_rect = candidate_quad->rect;
 
     // Reserve space in the quad list for the transparent quads.
     quad_list.ReplaceExistingElement<SolidColorDrawQuad>(
         candidate_iter_in_quad_list);
@@ skipping 12 matching lines @@
       SolidColorDrawQuad* transparent_quad =
           static_cast<SolidColorDrawQuad*>(*candidate_iter_in_quad_list);
       transparent_quad->SetAll(candidate_shared_quad_state,
                                quad_space_covered_rect, quad_space_covered_rect,
                                quad_space_covered_rect, false,
                                SK_ColorTRANSPARENT, true);
       ++candidate_iter_in_quad_list;
     }
   }
 
-  output_candidate_list->swap(new_candidate_list);
-  return true;
+  if (output_candidate_list->empty()) {
+    // Add our primary surface.
+    OverlayCandidate main_image;
+    main_image.display_rect = pixel_bounds;
+    output_candidate_list->push_back(main_image);
+  }
+
+  output_candidate_list->insert(output_candidate_list->end(),
+                                new_candidate_list.begin(),
+                                new_candidate_list.end());
+  return candidate_iter_in_quad_list;
 }
 
 }  // namespace cc