cc: Add readback and forced draw states to the Scheduler

cc/scheduler/scheduler_state_machine.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_STATE_MACHINE_H_
 #define CC_SCHEDULER_SCHEDULER_STATE_MACHINE_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 32 matching lines @@
     OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT,
     OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION,
   };
   static const char* OutputSurfaceStateToString(OutputSurfaceState state);
 
   enum CommitState {
     COMMIT_STATE_IDLE,
     COMMIT_STATE_FRAME_IN_PROGRESS,
     COMMIT_STATE_READY_TO_COMMIT,
     COMMIT_STATE_WAITING_FOR_FIRST_DRAW,
-    COMMIT_STATE_WAITING_FOR_FIRST_FORCED_DRAW,
   };
   static const char* CommitStateToString(CommitState state);
 
   enum TextureState {
     LAYER_TEXTURE_STATE_UNLOCKED,
     LAYER_TEXTURE_STATE_ACQUIRED_BY_MAIN_THREAD,
     LAYER_TEXTURE_STATE_ACQUIRED_BY_IMPL_THREAD,
   };
   static const char* TextureStateToString(TextureState state);
 
+  enum SynchronousReadbackState {
+    READBACK_STATE_IDLE,
+    READBACK_STATE_FORCED_COMMIT_REQUESTED,
+    READBACK_STATE_FORCED_COMMIT_PENDING,

[danakj, 2013/08/30 15:56:41]

This state enums are all different from each other in their verbage, and I am
finding it tricky to read and understand.

CommitState has FRAME_IN_PROGRESS... Forced redraw has WAITING_FOR_COMMIT...
This one has COMMIT_PENDING (and COMMIT_REQUESTED).

WDYT of..

READBACK_STATE_IDLE
READBACK_STATE_NEEDS_BEGIN_FRAME
READBACK_STATE_WAITING_FOR_COMMIT
READBACK_STATE_WAITING_FOR_ACTIVATION
READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK
READBACK_STATE_WAITING_FOR_REPLACEMENT_COMMIT
READBACK_STATE_WAITING_FOR_REPLACEMENT_ACTIVATION


FORCED_REDRAW_STATE_IDLE
FORCED_REDRAW_STATE_WAITING_FOR_COMMIT
FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION
FORCED_REDRAW_STATE_WAITING_FOR_DRAW



All of this said, I'm not sure I like moving the "needs_foo" state into this
enum. That's not a pattern we do elsewhere. needs states have been bools, with
enums acting as "we're waiting for this" not "we need to do this". Maybe you
could convince me why that's a good idea?

[brianderson, 2013/09/03 22:41:12]

I like your names, it is clearer what each state is waiting for.

I am actually tempted to move more of the needs_foo bools into existing enums. 
It directly encodes the reason why we need something, making the scheduler state
easier to decode at a glance without having to look at the code.

+    READBACK_STATE_WAITING_FOR_ACTIVATION,
+    READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK,
+    READBACK_STATE_REPLACEMENT_COMMIT_PENDING,
+    READBACK_STATE_REPLACEMENT_COMMIT_ACTIVATING,
+  };
+  static const char* SynchronousReadbackStateToString(
+      SynchronousReadbackState state);
+
+  enum ForcedRedrawOnTimeoutState {
+    FORCED_REDRAW_STATE_IDLE,
+    FORCED_REDRAW_STATE_WAITING_FOR_COMMIT,
+    FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION,
+    FORCED_REDRAW_STATE_WAITING_FOR_DRAW,
+  };
+  static const char* ForcedRedrawOnTimeoutStateToString(
+      ForcedRedrawOnTimeoutState state);
+
   bool CommitPending() const {
     return commit_state_ == COMMIT_STATE_FRAME_IN_PROGRESS ||
            commit_state_ == COMMIT_STATE_READY_TO_COMMIT;
   }
 
   bool RedrawPending() const { return needs_redraw_; }
 
   enum Action {
     ACTION_NONE,
     ACTION_SEND_BEGIN_FRAME_TO_MAIN_THREAD,
     ACTION_COMMIT,
     ACTION_UPDATE_VISIBLE_TILES,
     ACTION_ACTIVATE_PENDING_TREE,
-    ACTION_DRAW_IF_POSSIBLE,
-    ACTION_DRAW_FORCED,
+    ACTION_DRAW_AND_SWAP_IF_POSSIBLE,
+    ACTION_DRAW_AND_SWAP_FORCED,
     ACTION_DRAW_AND_SWAP_ABORT,
+    ACTION_DRAW_AND_READBACK,
     ACTION_BEGIN_OUTPUT_SURFACE_CREATION,
     ACTION_ACQUIRE_LAYER_TEXTURES_FOR_MAIN_THREAD,
   };
   static const char* ActionToString(Action action);
 
   scoped_ptr<base::Value> AsValue() const;
 
   Action NextAction() const;
   void UpdateState(Action action);
+  void CheckInvariants();
 
   // Indicates whether the main thread needs a begin frame callback in order to
   // make progress.
   bool BeginFrameNeededToDrawByImplThread() const;
   bool ProactiveBeginFrameWantedByImplThread() const;
 
   // Indicates that the system has entered and left a BeginFrame callback.
   // The scheduler will not draw more than once in a given BeginFrame
   // callback nor send more than one BeginFrame message.
   void DidEnterBeginFrame(const BeginFrameArgs& args);
   void DidLeaveBeginFrame();
   bool inside_begin_frame() const { return inside_begin_frame_; }
 
   // Indicates whether the LayerTreeHostImpl is visible.
   void SetVisible(bool visible);
 
   // Indicates that a redraw is required, either due to the impl tree changing
   // or the screen being damaged and simply needing redisplay.
   void SetNeedsRedraw();
 
-  // As SetNeedsRedraw(), but ensures the draw will definitely happen even if
-  // we are not visible.
-  void SetNeedsForcedRedraw();
-
   // Indicates that a redraw is required because we are currently rendering
   // with a low resolution or checkerboarded tile.
   void DidSwapUseIncompleteTile();
 
-  // Indicates whether ACTION_DRAW_IF_POSSIBLE drew to the screen or not.
+  // Indicates whether ACTION_DRAW_AND_SWAP_IF_POSSIBLE drew to the screen or
+  // not.
   void DidDrawIfPossibleCompleted(bool success);
 
   // Indicates that a new commit flow needs to be performed, either to pull
   // updates from the main thread to the impl, or to push deltas from the impl
   // thread to main.
   void SetNeedsCommit();
 
   // As SetNeedsCommit(), but ensures the begin frame will be sent to the main
   // thread even if we are not visible.  After this call we expect to go through
   // the forced commit flow and then return to waiting for a non-forced
   // begin frame to finish.
-  void SetNeedsForcedCommit();
+  void SetNeedsForcedCommitForReadback();
 
   // Call this only in response to receiving an
   // ACTION_SEND_BEGIN_FRAME_TO_MAIN_THREAD from NextAction.
   // Indicates that all painting is complete.
   void FinishCommit();
 
   // Call this only in response to receiving an
   // ACTION_SEND_BEGIN_FRAME_TO_MAIN_THREAD from NextAction if the client
   // rejects the begin frame message.  If did_handle is false, then
   // another commit will be retried soon.
   void BeginFrameAbortedByMainThread(bool did_handle);
 
   // Request exclusive access to the textures that back single buffered
   // layers on behalf of the main thread. Upon acquisition,
-  // ACTION_DRAW_IF_POSSIBLE will not draw until the main thread releases the
+  // ACTION_DRAW_AND_SWAP_IF_POSSIBLE will not draw until the main thread
+  // releases the
   // textures to the impl thread by committing the layers.
   void SetMainThreadNeedsLayerTextures();
 
   // Set that we can create the first OutputSurface and start the scheduler.
   void SetCanStart() { can_start_ = true; }
 
   // Indicates whether drawing would, at this time, make sense.
   // CanDraw can be used to supress flashes or checkerboarding
   // when such behavior would be undesirable.
   void SetCanDraw(bool can);
@@ skipping 32 matching lines @@
   bool HasSentBeginFrameToMainThreadThisFrame() const;
 
   void UpdateStateOnCommit(bool commit_was_aborted);
   void UpdateStateOnActivation();
   void UpdateStateOnDraw(bool did_swap);
 
   const SchedulerSettings settings_;
 
   OutputSurfaceState output_surface_state_;
   CommitState commit_state_;
+  TextureState texture_state_;
+  ForcedRedrawOnTimeoutState forced_redraw_state_;
+  SynchronousReadbackState readback_state_;
 
   int commit_count_;
   int current_frame_number_;
   int last_frame_number_where_begin_frame_sent_to_main_thread_;
-  int last_frame_number_where_draw_was_called_;
+  int last_frame_number_swap_performed_;
   int last_frame_number_where_update_visible_tiles_was_called_;
   int consecutive_failed_draws_;
   int maximum_number_of_failed_draws_before_draw_is_forced_;
   bool needs_redraw_;
   bool swap_used_incomplete_tile_;
-  bool needs_forced_redraw_;
-  bool needs_forced_redraw_after_next_commit_;
   bool needs_commit_;
-  bool needs_forced_commit_;
-  bool expect_immediate_begin_frame_for_main_thread_;
   bool main_thread_needs_layer_textures_;
   bool inside_begin_frame_;
   BeginFrameArgs last_begin_frame_args_;
   bool visible_;
   bool can_start_;
   bool can_draw_;
   bool has_pending_tree_;
   bool pending_tree_is_ready_for_activation_;
   bool active_tree_has_been_drawn_;
   bool draw_if_possible_failed_;
-  TextureState texture_state_;
   bool did_create_and_initialize_first_output_surface_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(SchedulerStateMachine);
 };
 
 }  // namespace cc
 
 #endif  // CC_SCHEDULER_SCHEDULER_STATE_MACHINE_H_