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// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef UI_ACCELERATED_WIDGET_MAC_CA_TRANSACTION_OBSERVER_H_
#define UI_ACCELERATED_WIDGET_MAC_CA_TRANSACTION_OBSERVER_H_
#include <set>
#include "base/functional/callback.h"
#include "base/no_destructor.h"
#include "base/observer_list.h"
#include "base/time/time.h"
#include "ui/accelerated_widget_mac/accelerated_widget_mac_export.h"
namespace ui {
// CATransactionCoordinator is an interface to undocumented macOS APIs which
// run callbacks at different stages of committing a CATransaction to the
// window server. There is no guarantee that it will call registered observers
// at all.
//
// - Pre-commit: After all outstanding CATransactions have committed and after
// layout, but before the new layer tree has been sent to the window server.
// Safe to block here waiting for drawing/layout in other processes (but
// you're on the main thread, so be reasonable).
//
// - Post-commit: After the new layer tree has been sent to the server but
// before the transaction has been finalized. In post-commit, the screen area
// occupied by the window and its shadow are frozen, so it's important to
// block as briefly as possible (well under a frame) or else artifacts will
// be visible around affected windows if screen content is changing behind
// them (think resizing a browser window while a video plays in a second
// window behind it). This is a great place to call -[CATransaction commit]
// (or otherwise flush pending changes to the screen) in other processes,
// because their updates will appear atomically.
//
// It has been observed that committing a CATransaction in the GPU process
// which changes which IOSurfaces are assigned to layers' contents is *faster*
// if done during the browser's post-commit phase vs. its pre-commit phase.
class ACCELERATED_WIDGET_MAC_EXPORT CATransactionCoordinator {
public:
class PreCommitObserver {
public:
virtual bool ShouldWaitInPreCommit() = 0;
virtual base::TimeDelta PreCommitTimeout() = 0;
};
// PostCommitObserver sub-classes must communicate with the IO thread. The
// CATransactionCoordinator will retain registered observers to ensure that
// they are not deleted while registered.
class PostCommitObserver
: public base::RefCountedThreadSafe<PostCommitObserver> {
public:
virtual void OnActivateForTransaction() = 0;
virtual void OnEnterPostCommit() = 0;
virtual bool ShouldWaitInPostCommit() = 0;
protected:
virtual ~PostCommitObserver() = default;
private:
friend class base::RefCountedThreadSafe<PostCommitObserver>;
};
static CATransactionCoordinator& Get();
CATransactionCoordinator(const CATransactionCoordinator&) = delete;
CATransactionCoordinator& operator=(const CATransactionCoordinator&) = delete;
void Synchronize();
void DisableForTesting() { disabled_for_testing_ = true; }
void AddPreCommitObserver(PreCommitObserver*);
void RemovePreCommitObserver(PreCommitObserver*);
void AddPostCommitObserver(scoped_refptr<PostCommitObserver>);
void RemovePostCommitObserver(scoped_refptr<PostCommitObserver>);
private:
friend class base::NoDestructor<CATransactionCoordinator>;
CATransactionCoordinator();
~CATransactionCoordinator();
void SynchronizeImpl();
void PreCommitHandler();
void PostCommitHandler();
bool active_ = false;
bool disabled_for_testing_ = false;
base::ObserverList<PreCommitObserver>::Unchecked pre_commit_observers_;
std::set<scoped_refptr<PostCommitObserver>> post_commit_observers_;
};
} // namespace ui
#endif // UI_ACCELERATED_WIDGET_MAC_CA_TRANSACTION_OBSERVER_H_
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