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..e59dac3537c08267663a22788fd9293e32762c42
--- /dev/null
+++ b/cc/scheduler/frame_source.h
@@ -0,0 +1,241 @@
+// 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"
+#include "ui/gfx/frame_time.h"
+
+namespace cc {
+
+/**
+ *
+ */
+class CC_EXPORT VSyncObserverImpl

[brianderson, 2014/09/13 01:38:12]

Maybe call this VSyncParameterObserver so it's clear this isn't the platform's
vsync signal.

+    : public ui::CompositorVSyncManager::Observer {
+ public:
+  VSyncObserverImpl(base::TimeTicks initial_vsync_timebase,
+                    base::TimeDelta initial_vsync_interval);
+  virtual ~VSyncObserverImpl();
+
+  virtual void OnUpdateVSyncParameters(
+      base::TimeTicks new_vsync_timebase,
+      base::TimeDelta new_vsync_interval) OVERRIDE;
+
+  virtual base::TimeTicks VSyncTimebase() const;
+  virtual base::TimeDelta VSyncInterval() const;
+
+  // Tracing support
+  virtual void AsValueInto(base::debug::TracedValue* dict) const;
+
+ protected:
+  virtual void OnTimeBaseAndIntervalChange(
+      const base::TimeTicks new_vsync_timebase,
+      const base::TimeDelta new_vsync_interval) {}
+
+ private:
+  base::TimeTicks vsync_timebase_;
+  base::TimeDelta vsync_interval_;
+};
+
+/**
+ *
+ */
+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;
+};
+
+/* Allows multiple observers to be connected to a single BeginFrameSource.
+class MultiBeginFrameObserver : public BeginFrameObserver {
+ public:
+  void AddObserver(BeginFrameObserver* obs) OVERRIDE {
+    observer_list_.AddObserver(obs);
+  }
+  void RemoveObserver(BeginFrameObserver* obs) OVERRIDE {
+    observer_list_.RemoveObserver(obs);
+  }
+
+  virtual void OnBeginFrame(const BeginFrameArgs& args) OVERRIDE {
+    FOR_EACH_OBSERVER(BeginFrameObserver, observer_list_, OnBeginFrame(args));
+  }
+ private:
+  ObserverList<BeginFrameObserver> observer_list_;
+};
+*/
+
+/**
+ *
+ */
+class CC_EXPORT BeginFrameSource {

[brianderson, 2014/09/13 01:38:12]

Would it make sense to split this into a BeginFrameSource and a
BeginFrameSender?

+ public:
+  virtual ~BeginFrameSource() {}
+
+  // Should the frame source be sending begin frames?
+  virtual bool NeedsBeginFrames() = 0;
+  virtual void SetNeedsBeginFrames(bool needs_begin_frames) = 0;
+  // This method provides backpressure to a frame source rather then toggling
+  // SetGenerateFrames. It is used by systems like the BackToBackFrameSource to
+  // make sure only one frame is pending at a time.
+  virtual void FinishedFrame(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:
+  void SendBeginFrame(const BeginFrameArgs& args);
+  BeginFrameObserver* observer_ = NULL;
+};
+
+/**
+ * A frame source which throttles down another begin frame source.
+ */
+class CC_EXPORT ThrottledBeginFrameSource : public BeginFrameSource,

[brianderson, 2014/09/13 01:38:13]

Let's keep this class out of this patch and add it if it makes sense when we
implement throttling. Although elegant, I'm not sure if this is the best
solution. Let's keep discussion about how to proceed with throttling in a
separate patch/bug.

+                                            public BeginFrameObserver {
+ public:
+  static scoped_ptr<ThrottledBeginFrameSource> Create(base::TimeDelta interval);
+  virtual ~ThrottledBeginFrameSource();
+
+  void SetMinimumInterval(base::TimeDelta new_minimum_interval);
+  virtual void AddSource(BeginFrameSource* new_source);
+  virtual void RemoveSource(BeginFrameSource* new_source);
+
+  // BeginFrameObserver
+  virtual void OnBeginFrame(const BeginFrameArgs& args) OVERRIDE;
+  virtual const BeginFrameArgs& LastBeginFrameArgs() const OVERRIDE;
+
+  // BeginFrameSource
+  virtual bool NeedsBeginFrames() OVERRIDE;
+  virtual void SetNeedsBeginFrames(bool needs_begin_frames) OVERRIDE;
+  virtual void FinishedFrame(size_t remaining_frames) OVERRIDE;
+
+  // Tracing
+  virtual void AsValueInto(base::debug::TracedValue* dict) const OVERRIDE;
+
+ protected:
+  explicit ThrottledBeginFrameSource(base::TimeDelta interval);
+
+  base::TimeDelta minimum_interval_;
+  BeginFrameSource* source_;
+};
+
+/**
+ * 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();
+
+  virtual void SendBeginFrameArgs();
+
+  // BeginFrameSource
+  virtual bool NeedsBeginFrames() OVERRIDE;
+  virtual void SetNeedsBeginFrames(bool needs_begin_frames) OVERRIDE;
+  virtual void FinishedFrame(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 ScheduleSendBeginFrameArgs();
+};
+
+/**
+ * A frame source which is locked an external vsync source and generates
+ * BeginFrameArgs for it.
+ */
+class CC_EXPORT SyntheticBeginFrameSource : public BeginFrameSource,
+                                            public VSyncObserverImpl,
+                                            public TimeSourceClient {
+ public:
+  static scoped_ptr<SyntheticBeginFrameSource> Create(
+      base::SingleThreadTaskRunner* task_runner,
+      base::TimeDelta initial_vsync_interval);
+  virtual ~SyntheticBeginFrameSource();
+
+  // TimeSourceClient
+  virtual void OnTimerTick() OVERRIDE;
+
+  // BeginFrameSource
+  virtual bool NeedsBeginFrames() OVERRIDE;
+  virtual void SetNeedsBeginFrames(bool needs_begin_frames) OVERRIDE;
+  virtual void FinishedFrame(size_t remaining_frames) OVERRIDE{};
+
+  // Tracing
+  virtual void AsValueInto(base::debug::TracedValue* dict) const OVERRIDE;
+
+ protected:
+  SyntheticBeginFrameSource(scoped_refptr<DelayBasedTimeSource> time_source,
+                            base::TimeTicks initial_vsync_timebase,
+                            base::TimeDelta initial_vsync_interval);
+
+  virtual void OnTimeBaseAndIntervalChange(
+      const base::TimeTicks new_vsync_timebase,
+      const base::TimeDelta new_vsync_interval) OVERRIDE;
+
+  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).
+ */
+class CC_EXPORT BeginFrameSourceMultiplexer : public ThrottledBeginFrameSource {
+ public:
+  static scoped_ptr<BeginFrameSourceMultiplexer> Create();
+  virtual ~BeginFrameSourceMultiplexer();
+
+  void SetActiveSource(BeginFrameSource* new_source);
+  const BeginFrameSource* ActiveSource();
+
+  // ThrottledBeginFrameSource
+  virtual void AddSource(BeginFrameSource* new_source) OVERRIDE;
+  virtual void RemoveSource(BeginFrameSource* existing_source) OVERRIDE;
+
+  // Tracing
+  virtual void AsValueInto(base::debug::TracedValue* dict) const OVERRIDE;
+
+ protected:
+  BeginFrameSourceMultiplexer();
+  explicit BeginFrameSourceMultiplexer(base::TimeDelta minimum_interval);
+
+ private:
+  bool HasSource(BeginFrameSource* source);
+  std::set<BeginFrameSource*> source_list_;
+};
+
+}  // namespace cc
+
+#endif  // CC_SCHEDULER_FRAME_SOURCE_H_