Refactoring the way begin frame sources inside scheduler work.

cc/scheduler/frame_source.h

Index: cc/scheduler/frame_source.h
diff --git a/cc/scheduler/frame_source.h b/cc/scheduler/frame_source.h
new file mode 100644
index 0000000000000000000000000000000000000000..a00cdd0e3bf45c534b786f1ce6e113c9761da799
--- /dev/null
+++ b/cc/scheduler/frame_source.h
@@ -0,0 +1,180 @@
+// Copyright 2014 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 CC_SCHEDULER_FRAME_SOURCE_H_
+#define CC_SCHEDULER_FRAME_SOURCE_H_
+
+#include <set>
+#include <string>
+
+#include "base/debug/trace_event.h"
+#include "base/logging.h"
+#include "cc/output/begin_frame_args.h"
+#include "cc/scheduler/delay_based_time_source.h"
+#include "ui/compositor/compositor_vsync_manager.h"
+
+namespace cc {
+
+/**
+ *
+ */
+class CC_EXPORT BeginFrameObserver {
+ public:
+  virtual const BeginFrameArgs& LastBeginFrameArgs() const = 0;
+  virtual void OnBeginFrame(const BeginFrameArgs& args) = 0;
+
+  // Tracing support
+  virtual void AsValueInto(base::debug::TracedValue* dict) const = 0;
+};
+
+/**
+ *
+ */
+class CC_EXPORT BeginFrameSource {
+ public:
+  virtual ~BeginFrameSource() {}
+
+  // Should the frame source be sending begin frames?
+  virtual bool NeedsBeginFrames() const = 0;
+  virtual void SetNeedsBeginFrames(bool needs_begin_frames) = 0;
+  // This method provides backpressure to a frame source rather than toggling
+  // SetNeedsBeginFrames. It is used by systems like the BackToBackFrameSource
+  // to make sure only one frame is pending at a time.
+  virtual void DidFinishFrame(size_t remaining_frames) = 0;
+
+  void AddObserver(BeginFrameObserver* obs);
+  void RemoveObserver(BeginFrameObserver* obs);
+
+  // Tracing support
+  virtual void AsValueInto(base::debug::TracedValue* dict) const = 0;
+
+ protected:
+  BeginFrameSource();
+  void CallOnBeginFrame(const BeginFrameArgs& args);
+  BeginFrameObserver* observer_;
+
+ private:
+  bool inside_as_value_into_;
+};
+
+/**
+ * A frame source which sends a BeginFrame as soon as remaining frames reaches
+ * zero.
+ */
+class CC_EXPORT BackToBackBeginFrameSource : public BeginFrameSource {
+ public:
+  static scoped_ptr<BackToBackBeginFrameSource> Create(
+      base::SingleThreadTaskRunner* task_runner);
+  virtual ~BackToBackBeginFrameSource();
+
+  // BeginFrameSource
+  virtual bool NeedsBeginFrames() const OVERRIDE;
+  virtual void SetNeedsBeginFrames(bool needs_begin_frames) OVERRIDE;
+  virtual void DidFinishFrame(size_t remaining_frames) OVERRIDE;
+
+  // Tracing
+  virtual void AsValueInto(base::debug::TracedValue* dict) const OVERRIDE;
+
+ protected:
+  explicit BackToBackBeginFrameSource(
+      base::SingleThreadTaskRunner* task_runner);
+  virtual base::TimeTicks Now();  // Now overridable for testing
+
+  base::WeakPtrFactory<BackToBackBeginFrameSource> weak_factory_;
+  base::SingleThreadTaskRunner* task_runner_;
+
+  bool needs_begin_frames_;
+  bool send_begin_frame_posted_;
+
+  void ScheduleBeginFrame();
+  void BeginFrame();
+};
+
+/**
+ * A frame source which is locked an external vsync source and generates
+ * BeginFrameArgs for it.
+ */
+class CC_EXPORT SyntheticBeginFrameSource
+    : public BeginFrameSource,
+      public ui::CompositorVSyncManager::Observer,
+      public TimeSourceClient {
+ public:
+  static scoped_ptr<SyntheticBeginFrameSource> Create(
+      base::SingleThreadTaskRunner* task_runner,
+      base::TimeTicks initial_vsync_timebase,
+      base::TimeDelta initial_vsync_interval);
+  virtual ~SyntheticBeginFrameSource();
+
+  // BeginFrameSource
+  virtual bool NeedsBeginFrames() const OVERRIDE;
+  virtual void SetNeedsBeginFrames(bool needs_begin_frames) OVERRIDE;
+  virtual void DidFinishFrame(size_t remaining_frames) OVERRIDE{};
+
+  // Tracing
+  virtual void AsValueInto(base::debug::TracedValue* dict) const OVERRIDE;
+
+  // ui::CompositorVSyncManager::Observer
+  virtual void OnUpdateVSyncParameters(
+      base::TimeTicks new_vsync_timebase,
+      base::TimeDelta new_vsync_interval) OVERRIDE;
+
+  // TimeSourceClient
+  virtual void OnTimerTick() OVERRIDE;
+
+ protected:
+  explicit SyntheticBeginFrameSource(
+      scoped_refptr<DelayBasedTimeSource> time_source);
+
+  void SendBeginFrameFromTick(base::TimeTicks frame_time);
+
+  scoped_refptr<DelayBasedTimeSource> time_source_;
+};
+
+/**
+ * A virtual frame source which lets you switch between multiple other frame
+ * sources while making sure the BeginFrameArgs stays increasing (possibly
+ * enforcing minimum boundry between BeginFrameArgs messages).
+ *
+ * The mux is an BeginFrameObserver as it needs to proxy the OnBeginFrame calls
+ * to preserves the monoticity of the BeginFrameArgs when switching sources.

[brianderson, 2014/09/18 21:54:19]

to preserve

[mithro-old, 2014/09/19 02:45:40]

Done.

+ */
+class CC_EXPORT BeginFrameSourceMultiplexer : public BeginFrameSource,
+                                              public BeginFrameObserver {
+ public:
+  static scoped_ptr<BeginFrameSourceMultiplexer> Create();
+  virtual ~BeginFrameSourceMultiplexer();
+
+  void SetMinimumInterval(base::TimeDelta new_minimum_interval);
+
+  void AddSource(BeginFrameSource* new_source);
+  void RemoveSource(BeginFrameSource* existing_source);
+  void SetActiveSource(BeginFrameSource* new_source);
+  const BeginFrameSource* ActiveSource();
+
+  // BeginFrameObserver
+  virtual void OnBeginFrame(const BeginFrameArgs& args) OVERRIDE;
+  virtual const BeginFrameArgs& LastBeginFrameArgs() const OVERRIDE;
+
+  // BeginFrameSource
+  virtual bool NeedsBeginFrames() const OVERRIDE;
+  virtual void SetNeedsBeginFrames(bool needs_begin_frames) OVERRIDE;
+  virtual void DidFinishFrame(size_t remaining_frames) OVERRIDE;
+
+  // Tracing
+  virtual void AsValueInto(base::debug::TracedValue* dict) const OVERRIDE;
+
+ protected:
+  BeginFrameSourceMultiplexer();
+  explicit BeginFrameSourceMultiplexer(base::TimeDelta minimum_interval);
+  bool HasSource(BeginFrameSource* source);
+
+  base::TimeDelta minimum_interval_;
+
+  BeginFrameSource* active_source_;
+  std::set<BeginFrameSource*> source_list_;
+};
+
+}  // namespace cc
+
+#endif  // CC_SCHEDULER_FRAME_SOURCE_H_