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// Copyright (c) 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 UI_COMPOSITOR_LAYER_OWNER_H_
#define UI_COMPOSITOR_LAYER_OWNER_H_
#include <memory>
#include "base/compiler_specific.h"
#include "base/macros.h"
#include "base/observer_list.h"
#include "ui/compositor/compositor_export.h"
#include "ui/compositor/layer.h"
namespace ui {
class COMPOSITOR_EXPORT LayerOwner {
public:
class Observer {
public:
// Called when the |layer()| of this LayerOwner has been recreated (i.e.
// RecreateLayer() was called). |old_layer| should not be retained after
// this as it may be destroyed soon.
// The new layer can be retrieved from LayerOwner::layer().
virtual void OnLayerRecreated(ui::Layer* old_layer) = 0;
protected:
virtual ~Observer() = default;
};
explicit LayerOwner(std::unique_ptr<Layer> layer = nullptr);
virtual ~LayerOwner();
void AddObserver(Observer* observer);
void RemoveObserver(Observer* observer);
// Releases the owning reference to its layer, and returns it.
// This is used when you need to animate the presentation of the owner just
// prior to destroying it. The Owner can be destroyed soon after calling this
// function, and the caller is then responsible for disposing of the layer
// once any animation completes. Note that layer() will remain valid until the
// end of ~LayerOwner().
std::unique_ptr<Layer> AcquireLayer();
// Similar to AcquireLayer(), but layer() will be set to nullptr immediately.
virtual std::unique_ptr<Layer> ReleaseLayer();
// Releases the ownership of the current layer, and takes ownership of
// |layer|.
void Reset(std::unique_ptr<Layer> layer);
// Asks the owner to recreate the layer, returning the old Layer. nullptr is
// returned if there is no existing layer, or recreate is not supported.
//
// This does not recurse. Existing children of the layer are moved to the new
// layer.
virtual std::unique_ptr<Layer> RecreateLayer();
ui::Layer* layer() { return layer_; }
const ui::Layer* layer() const { return layer_; }
bool OwnsLayer() const;
protected:
virtual void SetLayer(std::unique_ptr<Layer> layer);
void DestroyLayer();
private:
// The LayerOwner owns its layer unless ownership is relinquished via a call
// to AcquireLayer(). After that moment |layer_| will still be valid but
// |layer_owner_| will be nullptr. The reason for releasing ownership is that
// the client may wish to animate the layer beyond the lifetime of the owner,
// e.g. fading it out when it is destroyed.
std::unique_ptr<Layer> layer_owner_;
Layer* layer_ = nullptr;
base::ObserverList<Observer>::Unchecked observers_;
DISALLOW_COPY_AND_ASSIGN(LayerOwner);
};
} // namespace ui
#endif // UI_COMPOSITOR_LAYER_OWNER_H_