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/*
* Copyright (C) 2013 Google Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_ANIMATION_ANIMATION_CLOCK_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_ANIMATION_ANIMATION_CLOCK_H_
#include <limits>
#include "base/macros.h"
#include "base/time/default_tick_clock.h"
#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"
namespace blink {
// Maintains a stationary clock time during script execution. Tracks the glass
// time of the beginning of the current animation frame (i.e. the moment photons
// left the screen for the previous frame).
class CORE_EXPORT AnimationClock {
DISALLOW_NEW();
public:
AnimationClock()
: time_(),
can_dynamically_update_time_(false),
clock_(base::DefaultTickClock::GetInstance()),
task_for_which_time_was_calculated_(
std::numeric_limits<unsigned>::max()) {}
void UpdateTime(base::TimeTicks time);
base::TimeTicks CurrentTime();
// The HTML spec says that the clock for animations is only updated once per
// rendering lifecycle, at the start. However the spec also assumes that the
// user agent runs rendering lifecycles constantly, back-to-back. In Blink we
// attempt to *not* run rendering lifecycles as much as possible, to avoid
// unnecessary CPU usage.
//
// As such, when outside a rendering lifecycle (for example, if a setInterval
// triggers) we allow the AnimationClock to dynamically adjust its time to
// look like it is being updated by the rendering lifecycles that never
// happened.
//
// TODO(crbug.com/995806): Allowing the AnimationClock to update itself is
// error prone. We should instead get the latest impl-frame time from the
// compositor when outside of a Blink rendering lifecycle (whilst still
// not changing within the same task).
void SetAllowedToDynamicallyUpdateTime(bool can_dynamically_update_time) {
can_dynamically_update_time_ = can_dynamically_update_time;
}
// When using our dynamically update behavior outside rendering lifecycles, we
// still do not want the time to move forward within the same task (e.g.
// within a single setInterval callback). To achieve this we track the task in
// which the time was last updated, and don't update it again until we are in
// a new task.
static void NotifyTaskStart() { ++currently_running_task_; }
void ResetTimeForTesting();
// The caller owns the passed in clock, which must outlive the AnimationClock.
void OverrideDynamicClockForTesting(const base::TickClock*);
private:
base::TimeTicks time_;
// See |SetAllowedToDynamicallyUpdateTime| documentation for these members.
bool can_dynamically_update_time_;
const base::TickClock* clock_;
// See |NotifyTaskStart| documentation for these members.
unsigned task_for_which_time_was_calculated_;
static unsigned currently_running_task_;
DISALLOW_COPY_AND_ASSIGN(AnimationClock);
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_CORE_ANIMATION_ANIMATION_CLOCK_H_
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