cc: Control activation from the Scheduler

cc/scheduler/scheduler.h

 // Copyright 2011 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_SCHEDULER_H_
 #define CC_SCHEDULER_SCHEDULER_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 23 matching lines @@
 class SchedulerClient {
  public:
   virtual void SetNeedsBeginFrameOnImplThread(bool enable) = 0;
   virtual void ScheduledActionSendBeginFrameToMainThread() = 0;
   virtual ScheduledActionDrawAndSwapResult
   ScheduledActionDrawAndSwapIfPossible() = 0;
   virtual ScheduledActionDrawAndSwapResult
   ScheduledActionDrawAndSwapForced() = 0;
   virtual void ScheduledActionCommit() = 0;
   virtual void ScheduledActionUpdateVisibleTiles() = 0;
-  virtual void ScheduledActionActivatePendingTreeIfNeeded() = 0;
+  virtual void ScheduledActionActivatePendingTree() = 0;
   virtual void ScheduledActionBeginOutputSurfaceCreation() = 0;
   virtual void ScheduledActionAcquireLayerTexturesForMainThread() = 0;
   virtual void DidAnticipatedDrawTimeChange(base::TimeTicks time) = 0;
   virtual base::TimeDelta DrawDurationEstimate() = 0;
   virtual base::TimeDelta BeginFrameToCommitDurationEstimate() = 0;
   virtual base::TimeDelta CommitToActivateDurationEstimate() = 0;
 
  protected:
   virtual ~SchedulerClient() {}
 };
 
 class CC_EXPORT Scheduler {
  public:
   static scoped_ptr<Scheduler> Create(
       SchedulerClient* client,
       const SchedulerSettings& scheduler_settings) {
     return make_scoped_ptr(new Scheduler(client,  scheduler_settings));
   }
 
   virtual ~Scheduler();
 
   void SetCanStart();
 
   void SetVisible(bool visible);
   void SetCanDraw(bool can_draw);
-  void SetHasPendingTree(bool has_pending_tree);
+  void NotifyReadyToActivate();
+  void SetHasTrees(bool has_pending_tree,  bool active_tree_is_null);

[reveman, 2013/08/23 16:16:48]

has_active_tree? find it confusing that active tree flags is inverted but not
the pending tree flag.

[enne (OOO), 2013/08/23 17:54:09]

Doesn't the scheduler already know this information?  For example, the
commit_results_in_pending_tree that you added in the other patch.  It seems like
either the Scheduler should assume the tree state based on commit/activate/abort
actions or it should be told explicitly, but not a little of both.

[brianderson, 2013/08/23 18:17:38]

Hmm. I used active_tree_is_null because, technically, there is an active tree in
LTHI, it's just that it's root layer is null. From the point of view of the
Scheduler though, we might as well use has_active_tree.  I'll change it if we
are going to keep it.

[brianderson, 2013/08/23 18:17:38]

Is it safe to assume that the active tree's root layer is not null after the
first commit/activation for the lifetime of the Scheduler class?

[enne (OOO), 2013/08/23 18:30:35]

Ok, good point.  I don't think we do, but I think it's technically possible.

That said, it seems like you're only using active_tree_is_null to check in
ShouldActivatePendingTree() to avoid spurious aborted draws before the first
activation.  You could maybe replace that with bool has_ever_activated_, which
the scheduler definitely knows about.

 
   void SetNeedsCommit();
 
   // Like SetNeedsCommit(), but ensures a commit will definitely happen even if
   // we are not visible.
   void SetNeedsForcedCommit();
 
   void SetNeedsRedraw();
 
   void SetMainThreadNeedsLayerTextures();
@@ skipping 50 matching lines @@
 
   SchedulerStateMachine state_machine_;
   bool inside_process_scheduled_actions_;
 
   DISALLOW_COPY_AND_ASSIGN(Scheduler);
 };
 
 }  // namespace cc
 
 #endif  // CC_SCHEDULER_SCHEDULER_H_