Unified BeginFrame scheduling

cc/scheduler/begin_frame_manager.h

+// 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_BEGIN_FRAME_MANAGER_H_
+#define CC_SCHEDULER_BEGIN_FRAME_MANAGER_H_
+
+#include "base/basictypes.h"
+#include "base/observer_list.h"
+#include "base/threading/non_thread_safe.h"
+#include "base/time/time.h"
+#include "cc/base/cc_export.h"
+#include "cc/output/begin_frame_args.h"
+
+namespace cc {
+
+struct BeginFrameArgs;
+
+// This class delivers a BeginFrame request from the Compositor to its
+// observers. It also handles next BeginFrame scheduling via its delegate.
+// Browser compositor will own this.
+// This class will be run only on main thread.
+class CC_EXPORT BeginFrameManager : public base::NonThreadSafe {
+ public:
+  // Subclass should deliver BeginFrame to its client.
+  class Observer {
+   public:
+    virtual void OnSendBeginFrame(const BeginFrameArgs& args) = 0;
+  };
+
+  // Subclass(Scheduler) should implement how to schedule next BeginFrame.
+  class Delegate {
+   public:
+    virtual void SetChildrenNeedBeginFrames(bool need_begin_frame) = 0;
+
+    // The "authoritative" vsync interval, if provided, will override interval
+    // reported from 3D context. This is typically the value reported by a more
+    // reliable source, e.g, the platform display configuration.
+    // In the particular case of ChromeOS -- this is the value queried through
+    // XRandR, which is more reliable than the value queried through the 3D
+    // context.
+    virtual void SetAuthoritativeVSyncInterval(base::TimeDelta interval) = 0;
+
+    // When we want to use platform provided refresh rate instead of internal
+    // timer, compositor will deliver it by calling this function.
+    virtual void StartBeginFrame(const BeginFrameArgs& args) = 0;
+  };
+
+  BeginFrameManager();
+  ~BeginFrameManager();
+
+  void set_delegate(Delegate* delegate) {
+    DCHECK(!delegate_) <<
+        "BeginFrameManager::Delegate is allowed to set only once";
+    delegate_ = delegate;
+  }
+
+  // Send BeginFrame to observers.
+  void SendBeginFrameToChildren(const BeginFrameArgs& args);
+
+  // See the comment of Delegate::SetAuthritativeVSyncInterval.
+  void SetAuthoritativeVSyncInterval(base::TimeDelta interval) const;
+
+  void AddObserver(
+      Observer* observer,
+      const BeginFrameArgs& last_begin_frame_args_sent_to_observer);
+  void RemoveObserver(Observer* observer);
+
+ private:
+  // Not owned by this class.
+  Delegate* delegate_;
+
+  // Number of BeginFrameManager's observer.
+  int num_of_observers_;
+
+  // Used to send to any new observers immediately.
+  BeginFrameArgs last_begin_frame_args_;
+
+  ObserverList<Observer> observer_list_;
+
+  DISALLOW_COPY_AND_ASSIGN(BeginFrameManager);
+};
+
+}  // namespace cc
+
+#endif  // CC_SCHEDULER_BEGIN_FRAME_MANAGER_H_