src/cc/trees/occlusion.cc

   1 // Copyright 2014 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.h"
   6
   7 #include "cc/base/math_util.h"
   8 #include "ui/gfx/rect.h"
   9
  10 namespace cc {
  11
  12 Occlusion::Occlusion() {
  13 }
  14
  15 Occlusion::Occlusion(const gfx::Transform& draw_transform,
  16                      const SimpleEnclosedRegion& occlusion_from_outside_target,
  17                      const SimpleEnclosedRegion& occlusion_from_inside_target)
  18     : draw_transform_(draw_transform),
  19       occlusion_from_outside_target_(occlusion_from_outside_target),
  20       occlusion_from_inside_target_(occlusion_from_inside_target) {
  21 }
  22
  23 bool Occlusion::IsOccluded(const gfx::Rect& content_rect) const {
  24   if (content_rect.IsEmpty())
  25     return true;
  26
  27   if (occlusion_from_inside_target_.IsEmpty() &&
  28       occlusion_from_outside_target_.IsEmpty()) {
  29     return false;
  30   }
  31
  32   gfx::Rect unoccluded_rect_in_target_surface =
  33       GetUnoccludedRectInTargetSurface(content_rect);
  34   return unoccluded_rect_in_target_surface.IsEmpty();
  35 }
  36
  37 gfx::Rect Occlusion::GetUnoccludedContentRect(
  38     const gfx::Rect& content_rect) const {
  39   if (content_rect.IsEmpty())
  40     return content_rect;
  41
  42   if (occlusion_from_inside_target_.IsEmpty() &&
  43       occlusion_from_outside_target_.IsEmpty()) {
  44     return content_rect;
  45   }
  46
  47   gfx::Rect unoccluded_rect_in_target_surface =
  48       GetUnoccludedRectInTargetSurface(content_rect);
  49   if (unoccluded_rect_in_target_surface.IsEmpty())
  50     return gfx::Rect();
  51
  52   gfx::Transform inverse_draw_transform(gfx::Transform::kSkipInitialization);
  53   bool ok = draw_transform_.GetInverse(&inverse_draw_transform);
  54   DCHECK(ok);
  55
  56   gfx::Rect unoccluded_rect = MathUtil::ProjectEnclosingClippedRect(
  57       inverse_draw_transform, unoccluded_rect_in_target_surface);
  58   unoccluded_rect.Intersect(content_rect);
  59
  60   return unoccluded_rect;
  61 }
  62
  63 gfx::Rect Occlusion::GetUnoccludedRectInTargetSurface(
  64     const gfx::Rect& content_rect) const {
  65   // Take the ToEnclosingRect at each step, as we want to contain any unoccluded
  66   // partial pixels in the resulting Rect.
  67   gfx::Rect unoccluded_rect_in_target_surface =
  68       MathUtil::MapEnclosingClippedRect(draw_transform_, content_rect);
  69   DCHECK_LE(occlusion_from_inside_target_.GetRegionComplexity(), 1u);
  70   DCHECK_LE(occlusion_from_outside_target_.GetRegionComplexity(), 1u);
  71   // These subtract operations are more lossy than if we did both operations at
  72   // once.
  73   unoccluded_rect_in_target_surface.Subtract(
  74       occlusion_from_inside_target_.bounds());
  75   unoccluded_rect_in_target_surface.Subtract(
  76       occlusion_from_outside_target_.bounds());
  77
  78   return unoccluded_rect_in_target_surface;
  79 }
  80
  81 }  // namespace cc