ui/compositor/compositor_vsync_manager.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef UI_COMPOSITOR_COMPOSITOR_VSYNC_MANAGER_H_
   6 #define UI_COMPOSITOR_COMPOSITOR_VSYNC_MANAGER_H_
   7
   8 #include "base/memory/ref_counted.h"
   9 #include "base/observer_list_threadsafe.h"
  10 #include "base/synchronization/lock.h"
  11 #include "base/time/time.h"
  12 #include "ui/compositor/compositor_export.h"
  13
  14 namespace ui {
  15
  16 // This class manages vsync parameters for a compositor. It merges updates of
  17 // the parameters from different sources and sends the merged updates to
  18 // observers which register to it. This class is explicitly synchronized and is
  19 // safe to use and update from any thread. Observers of the manager will be
  20 // notified on the thread they have registered from, and should be removed from
  21 // the same thread.
  22 class COMPOSITOR_EXPORT CompositorVSyncManager
  23     : public base::RefCountedThreadSafe<CompositorVSyncManager> {
  24  public:
  25   class Observer {
  26    public:
  27     virtual void OnUpdateVSyncParameters(base::TimeTicks timebase,
  28                                          base::TimeDelta interval) = 0;
  29   };
  30
  31   CompositorVSyncManager();
  32
  33   // The "authoritative" vsync interval, if provided, will override |interval|
  34   // as reported by UpdateVSyncParameters() whenever it is called.  This is
  35   // typically the value reported by a more reliable source, e.g. the platform
  36   // display configuration.  In the particular case of ChromeOS -- this is the
  37   // value queried through XRandR, which is more reliable than the value
  38   // queried through the 3D context.
  39   void SetAuthoritativeVSyncInterval(base::TimeDelta interval);
  40
  41   // The vsync parameters consist of |timebase|, which is the platform timestamp
  42   // of the last vsync, and |interval|, which is the interval between vsyncs.
  43   // |interval| may be overriden by SetAuthoritativeVSyncInterval() above.
  44   void UpdateVSyncParameters(base::TimeTicks timebase,
  45                              base::TimeDelta interval);
  46
  47   void AddObserver(Observer* observer);
  48   void RemoveObserver(Observer* observer);
  49
  50  private:
  51   friend class base::RefCountedThreadSafe<CompositorVSyncManager>;
  52
  53   ~CompositorVSyncManager();
  54
  55   void NotifyObservers(base::TimeTicks timebase, base::TimeDelta interval);
  56
  57   // List of observers.
  58   scoped_refptr<ObserverListThreadSafe<Observer> > observer_list_;
  59
  60   // Protects the cached vsync parameters below.
  61   base::Lock vsync_parameters_lock_;
  62   base::TimeTicks last_timebase_;
  63   base::TimeDelta last_interval_;
  64   base::TimeDelta authoritative_vsync_interval_;
  65
  66   DISALLOW_COPY_AND_ASSIGN(CompositorVSyncManager);
  67 };
  68
  69 }  // namespace ui
  70
  71 #endif  // UI_COMPOSITOR_COMPOSITOR_VSYNC_MANAGER_H_