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5a2244c581
* Reland path volatility tracker (#23063)" (#23220) This reverts commit fceef3aaa9d156e8ec3f4a079c142921882f70d8. * allow disabling based on whether deterministic rendering is needed
83 lines
2.6 KiB
C++
83 lines
2.6 KiB
C++
// Copyright 2013 The Flutter Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef FLUTTER_LIB_VOLATILE_PATH_TRACKER_H_
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#define FLUTTER_LIB_VOLATILE_PATH_TRACKER_H_
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#include <deque>
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#include <mutex>
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#include <set>
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#include "flutter/fml/macros.h"
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#include "flutter/fml/task_runner.h"
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#include "flutter/fml/trace_event.h"
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#include "third_party/skia/include/core/SkPath.h"
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namespace flutter {
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/// A cache for paths drawn from dart:ui.
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///
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/// Whenever a flutter::CanvasPath is created, it must Insert an entry into
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/// this cache. Whenever a frame is drawn, the shell must call OnFrame. The
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/// cache will flip the volatility bit on the SkPath and remove it from the
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/// cache. If the Dart object is released, Erase must be called to avoid
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/// tracking a path that is no longer referenced in Dart code.
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///
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/// Enabling this cache may cause difficult to predict minor pixel differences
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/// when paths are rendered. If deterministic rendering is needed, e.g. for a
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/// screen diffing test, this class will not cache any paths and will
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/// automatically set the volatility of the path to false.
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class VolatilePathTracker {
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public:
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/// The fields of this struct must only accessed on the UI task runner.
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struct TrackedPath {
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bool tracking_volatility = false;
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int frame_count = 0;
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SkPath path;
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};
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VolatilePathTracker(fml::RefPtr<fml::TaskRunner> ui_task_runner,
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bool enabled);
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static constexpr int kFramesOfVolatility = 2;
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// Starts tracking a path.
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// Must be called from the UI task runner.
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//
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// Callers should only insert paths that are currently volatile.
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void Insert(std::shared_ptr<TrackedPath> path);
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// Removes a path from tracking.
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//
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// May be called from any thread.
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void Erase(std::shared_ptr<TrackedPath> path);
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// Called by the shell at the end of a frame after notifying Dart about idle
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// time.
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//
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// This method will flip the volatility bit to false for any paths that have
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// survived the |kFramesOfVolatility|.
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//
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// Must be called from the UI task runner.
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void OnFrame();
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bool enabled() const { return enabled_; }
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private:
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fml::RefPtr<fml::TaskRunner> ui_task_runner_;
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std::atomic_bool needs_drain_ = false;
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std::mutex paths_to_remove_mutex_;
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std::deque<std::shared_ptr<TrackedPath>> paths_to_remove_;
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std::set<std::shared_ptr<TrackedPath>> paths_;
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bool enabled_ = true;
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void Drain();
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FML_DISALLOW_COPY_AND_ASSIGN(VolatilePathTracker);
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};
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} // namespace flutter
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#endif // FLUTTER_LIB_VOLATILE_PATH_TRACKER_H_
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