chromium/cc/layers/effect_tree_layer_list_iterator.h

// Copyright 2017 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CC_LAYERS_EFFECT_TREE_LAYER_LIST_ITERATOR_H_
#define CC_LAYERS_EFFECT_TREE_LAYER_LIST_ITERATOR_H_

#include "base/memory/raw_ptr_exclusion.h"
#include "base/notreached.h"
#include "cc/cc_export.h"
#include "cc/trees/effect_node.h"
#include "cc/trees/layer_tree_impl.h"
#include "cc/trees/property_tree.h"

namespace cc {

class LayerImpl;
class LayerTreeImpl;

// This iterates over layers and render surfaces in front-to-back order (that
// is, in reverse-draw-order). Only layers that draw content to some render
// surface are visited. A render surface is visited immediately after all
// layers and surfaces that contribute content to that surface are visited.
// Surfaces are first visited in state kTargetSurface. Immediately after that,
// every surface other than the root surface is visited in state
// kContributingSurface, as it contributes to the next target surface.
//
// The iterator takes on the following states:
// 1. kLayer: The iterator is visiting layer |current_layer()| that contributes
//    to surface |target_render_surface()|.
// 2. kTargetSurface: The iterator is visiting render surface
//    |target_render_surface()|.
// 3. kContributingSurface: The iterator is visiting render surface
//    |current_render_surface()| that contributes to surface
//    |target_render_surface()|.
// 4. kEnd: All layers and render surfaces have already been visited.
class CC_EXPORT EffectTreeLayerListIterator { … };

}  // namespace cc

#endif  // CC_LAYERS_EFFECT_TREE_LAYER_LIST_ITERATOR_H_