cc/trees/occlusion_tracker.h - chromium/src - Git at Google

 // Copyright 2012 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.

 #ifndef CC_TREES_OCCLUSION_TRACKER_H_
 #define CC_TREES_OCCLUSION_TRACKER_H_

 #include <vector>

 #include "base/macros.h"
 #include "cc/base/simple_enclosed_region.h"
 #include "cc/cc_export.h"
 #include "cc/layers/effect_tree_layer_list_iterator.h"
 #include "cc/trees/occlusion.h"
 #include "ui/gfx/geometry/rect.h"

 namespace cc {
 class LayerImpl;
 class Region;
 class RenderSurfaceImpl;

 // This class is used to track occlusion of layers while traversing them in a
 // front-to-back order. As each layer is visited, one of the methods in this
 // class is called to notify it about the current target surface. Then,
 // occlusion in the content space of the current layer may be queried, via
 // Occlusion from GetCurrentOcclusionForLayer(). If the current layer owns a
 // RenderSurfaceImpl, then occlusion on that RenderSurfaceImpl may also be
 // queried via surfaceOccluded() and surfaceUnoccludedContentRect(). Finally,
 // once finished with the layer, occlusion behind the layer should be marked by
 // calling MarkOccludedBehindLayer().
 class CC_EXPORT OcclusionTracker {
  public:
   explicit OcclusionTracker(const gfx::Rect& screen_space_clip_rect);
   ~OcclusionTracker();

   // Return an occlusion that retains the current state of the tracker
   // and can be used outside of a layer walk to check occlusion.
   Occlusion GetCurrentOcclusionForLayer(
       const gfx::Transform& draw_transform) const;
   Occlusion GetCurrentOcclusionForContributingSurface(
       const gfx::Transform& draw_transform) const;

   const RenderSurfaceImpl* OcclusionSurfaceForContributingSurface() const;
   // Called at the beginning of each step in EffectTreeLayerListIterator's
   // front-to-back traversal.
   void EnterLayer(const EffectTreeLayerListIterator::Position& iterator);
   // Called at the end of each step in EffectTreeLayerListIterator's
   // front-to-back traversal.
   void LeaveLayer(const EffectTreeLayerListIterator::Position& iterator);

   // Gives the region of the screen that is not occluded by something opaque.
   Region ComputeVisibleRegionInScreen(const LayerTreeImpl* layer_tree) const;

   void set_minimum_tracking_size(const gfx::Size& size) {
     minimum_tracking_size_ = size;
   }

  protected:
   struct StackObject {
     StackObject() : target(0) {}
     explicit StackObject(const RenderSurfaceImpl* target) : target(target) {}
     const RenderSurfaceImpl* target;
     SimpleEnclosedRegion occlusion_from_outside_target;
     SimpleEnclosedRegion occlusion_from_inside_target;
   };

   // The stack holds occluded regions for subtrees in the
   // RenderSurfaceImpl-Layer tree, so that when we leave a subtree we may apply
   // a mask to it, but not to the parts outside the subtree.
   // - The first time we see a new subtree under a target, we add that target to
   // the top of the stack. This can happen as a layer representing itself, or as
   // a target surface.
   // - When we visit a target surface, we apply its mask to its subtree, which
   // is at the top of the stack.
   // - When we visit a layer representing itself, we add its occlusion to the
   // current subtree, which is at the top of the stack.
   // - When we visit a layer representing a contributing surface, the current
   // target will never be the top of the stack since we just came from the
   // contributing surface.
   // We merge the occlusion at the top of the stack with the new current
   // subtree. This new target is pushed onto the stack if not already there.
   std::vector<StackObject> stack_;

  private:
   // Called when visiting a layer. If the target was not already current, then
   // this indicates we have entered a new surface subtree.
   void EnterRenderTarget(const RenderSurfaceImpl* new_target_surface);

   // Called when visiting a target surface. This indicates we have visited all
   // the layers within the surface, and we may perform any surface-wide
   // operations.
   void FinishedRenderTarget(const RenderSurfaceImpl* finished_target_surface);

   // Called when visiting a contributing surface. This indicates that we are
   // leaving our current surface, and entering the new one. We then perform any
   // operations required for merging results from the child subtree into its
   // parent.
   void LeaveToRenderTarget(const RenderSurfaceImpl* new_target_surface);

   // Add the layer's occlusion to the tracked state.
   void MarkOccludedBehindLayer(const LayerImpl* layer);

   gfx::Rect screen_space_clip_rect_;
   gfx::Size minimum_tracking_size_;

   DISALLOW_COPY_AND_ASSIGN(OcclusionTracker);
 };

 }  // namespace cc

 #endif  // CC_TREES_OCCLUSION_TRACKER_H_
	// Copyright 2012 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.

	#ifndef CC_TREES_OCCLUSION_TRACKER_H_
	#define CC_TREES_OCCLUSION_TRACKER_H_

	#include <vector>

	#include "base/macros.h"
	#include "cc/base/simple_enclosed_region.h"
	#include "cc/cc_export.h"
	#include "cc/layers/effect_tree_layer_list_iterator.h"
	#include "cc/trees/occlusion.h"
	#include "ui/gfx/geometry/rect.h"

	namespace cc {
	class LayerImpl;
	class Region;
	class RenderSurfaceImpl;

	// This class is used to track occlusion of layers while traversing them in a
	// front-to-back order. As each layer is visited, one of the methods in this
	// class is called to notify it about the current target surface. Then,
	// occlusion in the content space of the current layer may be queried, via
	// Occlusion from GetCurrentOcclusionForLayer(). If the current layer owns a
	// RenderSurfaceImpl, then occlusion on that RenderSurfaceImpl may also be
	// queried via surfaceOccluded() and surfaceUnoccludedContentRect(). Finally,
	// once finished with the layer, occlusion behind the layer should be marked by
	// calling MarkOccludedBehindLayer().
	class CC_EXPORT OcclusionTracker {
	public:
	explicit OcclusionTracker(const gfx::Rect& screen_space_clip_rect);
	~OcclusionTracker();

	// Return an occlusion that retains the current state of the tracker
	// and can be used outside of a layer walk to check occlusion.
	Occlusion GetCurrentOcclusionForLayer(
	const gfx::Transform& draw_transform) const;
	Occlusion GetCurrentOcclusionForContributingSurface(
	const gfx::Transform& draw_transform) const;

	const RenderSurfaceImpl* OcclusionSurfaceForContributingSurface() const;
	// Called at the beginning of each step in EffectTreeLayerListIterator's
	// front-to-back traversal.
	void EnterLayer(const EffectTreeLayerListIterator::Position& iterator);
	// Called at the end of each step in EffectTreeLayerListIterator's
	// front-to-back traversal.
	void LeaveLayer(const EffectTreeLayerListIterator::Position& iterator);

	// Gives the region of the screen that is not occluded by something opaque.
	Region ComputeVisibleRegionInScreen(const LayerTreeImpl* layer_tree) const;

	void set_minimum_tracking_size(const gfx::Size& size) {
	minimum_tracking_size_ = size;
	}

	protected:
	struct StackObject {
	StackObject() : target(0) {}
	explicit StackObject(const RenderSurfaceImpl* target) : target(target) {}
	const RenderSurfaceImpl* target;
	SimpleEnclosedRegion occlusion_from_outside_target;
	SimpleEnclosedRegion occlusion_from_inside_target;
	};

	// The stack holds occluded regions for subtrees in the
	// RenderSurfaceImpl-Layer tree, so that when we leave a subtree we may apply
	// a mask to it, but not to the parts outside the subtree.
	// - The first time we see a new subtree under a target, we add that target to
	// the top of the stack. This can happen as a layer representing itself, or as
	// a target surface.
	// - When we visit a target surface, we apply its mask to its subtree, which
	// is at the top of the stack.
	// - When we visit a layer representing itself, we add its occlusion to the
	// current subtree, which is at the top of the stack.
	// - When we visit a layer representing a contributing surface, the current
	// target will never be the top of the stack since we just came from the
	// contributing surface.
	// We merge the occlusion at the top of the stack with the new current
	// subtree. This new target is pushed onto the stack if not already there.
	std::vector<StackObject> stack_;

	private:
	// Called when visiting a layer. If the target was not already current, then
	// this indicates we have entered a new surface subtree.
	void EnterRenderTarget(const RenderSurfaceImpl* new_target_surface);

	// Called when visiting a target surface. This indicates we have visited all
	// the layers within the surface, and we may perform any surface-wide
	// operations.
	void FinishedRenderTarget(const RenderSurfaceImpl* finished_target_surface);

	// Called when visiting a contributing surface. This indicates that we are
	// leaving our current surface, and entering the new one. We then perform any
	// operations required for merging results from the child subtree into its
	// parent.
	void LeaveToRenderTarget(const RenderSurfaceImpl* new_target_surface);

	// Add the layer's occlusion to the tracked state.
	void MarkOccludedBehindLayer(const LayerImpl* layer);

	gfx::Rect screen_space_clip_rect_;
	gfx::Size minimum_tracking_size_;

	DISALLOW_COPY_AND_ASSIGN(OcclusionTracker);
	};

	} // namespace cc

	#endif // CC_TREES_OCCLUSION_TRACKER_H_