cc/scheduler/scheduler_state_machine.h

   1 // Copyright 2011 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 CC_SCHEDULER_SCHEDULER_STATE_MACHINE_H_
   6 #define CC_SCHEDULER_SCHEDULER_STATE_MACHINE_H_
   7
   8 #include <string>
   9
  10 #include "base/basictypes.h"
  11 #include "base/memory/scoped_ptr.h"
  12 #include "base/time/time.h"
  13 #include "cc/base/cc_export.h"
  14 #include "cc/output/begin_frame_args.h"
  15 #include "cc/scheduler/scheduler_settings.h"
  16
  17 namespace base {
  18 class Value;
  19 }
  20
  21 namespace cc {
  22
  23 // The SchedulerStateMachine decides how to coordinate main thread activites
  24 // like painting/running javascript with rendering and input activities on the
  25 // impl thread.
  26 //
  27 // The state machine tracks internal state but is also influenced by external
  28 // state.  Internal state includes things like whether a frame has been
  29 // requested, while external state includes things like the current time being
  30 // near to the vblank time.
  31 //
  32 // The scheduler seperates "what to do next" from the updating of its internal
  33 // state to make testing cleaner.
  34 class CC_EXPORT SchedulerStateMachine {
  35  public:
  36   // settings must be valid for the lifetime of this class.
  37   explicit SchedulerStateMachine(const SchedulerSettings& settings);
  38
  39   enum OutputSurfaceState {
  40     OUTPUT_SURFACE_ACTIVE,
  41     OUTPUT_SURFACE_LOST,
  42     OUTPUT_SURFACE_CREATING,
  43     OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT,
  44     OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION,
  45   };
  46   static const char* OutputSurfaceStateToString(OutputSurfaceState state);
  47
  48   enum CommitState {
  49     COMMIT_STATE_IDLE,
  50     COMMIT_STATE_FRAME_IN_PROGRESS,
  51     COMMIT_STATE_READY_TO_COMMIT,
  52     COMMIT_STATE_WAITING_FOR_FIRST_DRAW,
  53     COMMIT_STATE_WAITING_FOR_FIRST_FORCED_DRAW,
  54   };
  55   static const char* CommitStateToString(CommitState state);
  56
  57   enum TextureState {
  58     LAYER_TEXTURE_STATE_UNLOCKED,
  59     LAYER_TEXTURE_STATE_ACQUIRED_BY_MAIN_THREAD,
  60     LAYER_TEXTURE_STATE_ACQUIRED_BY_IMPL_THREAD,
  61   };
  62   static const char* TextureStateToString(TextureState state);
  63
  64   bool CommitPending() const {
  65     return commit_state_ == COMMIT_STATE_FRAME_IN_PROGRESS ||
  66            commit_state_ == COMMIT_STATE_READY_TO_COMMIT;
  67   }
  68
  69   bool RedrawPending() const { return needs_redraw_; }
  70
  71   enum Action {
  72     ACTION_NONE,
  73     ACTION_SEND_BEGIN_FRAME_TO_MAIN_THREAD,
  74     ACTION_COMMIT,
  75     ACTION_UPDATE_VISIBLE_TILES,
  76     ACTION_ACTIVATE_PENDING_TREE,
  77     ACTION_DRAW_IF_POSSIBLE,
  78     ACTION_DRAW_FORCED,
  79     ACTION_DRAW_AND_SWAP_ABORT,
  80     ACTION_BEGIN_OUTPUT_SURFACE_CREATION,
  81     ACTION_ACQUIRE_LAYER_TEXTURES_FOR_MAIN_THREAD,
  82   };
  83   static const char* ActionToString(Action action);
  84
  85   scoped_ptr<base::Value> AsValue() const;
  86
  87   Action NextAction() const;
  88   void UpdateState(Action action);
  89
  90   // Indicates whether the main thread needs a begin frame callback in order to
  91   // make progress.
  92   bool BeginFrameNeededToDrawByImplThread() const;
  93   bool ProactiveBeginFrameWantedByImplThread() const;
  94
  95   // Indicates that the system has entered and left a BeginFrame callback.
  96   // The scheduler will not draw more than once in a given BeginFrame
  97   // callback nor send more than one BeginFrame message.
  98   void DidEnterBeginFrame(const BeginFrameArgs& args);
  99   void DidLeaveBeginFrame();
 100   bool inside_begin_frame() const { return inside_begin_frame_; }
 101
 102   // Indicates whether the LayerTreeHostImpl is visible.
 103   void SetVisible(bool visible);
 104
 105   // Indicates that a redraw is required, either due to the impl tree changing
 106   // or the screen being damaged and simply needing redisplay.
 107   void SetNeedsRedraw();
 108
 109   // As SetNeedsRedraw(), but ensures the draw will definitely happen even if
 110   // we are not visible.
 111   void SetNeedsForcedRedraw();
 112
 113   // Indicates that a redraw is required because we are currently rendering
 114   // with a low resolution or checkerboarded tile.
 115   void DidSwapUseIncompleteTile();
 116
 117   // Indicates whether ACTION_DRAW_IF_POSSIBLE drew to the screen or not.
 118   void DidDrawIfPossibleCompleted(bool success);
 119
 120   // Indicates that a new commit flow needs to be performed, either to pull
 121   // updates from the main thread to the impl, or to push deltas from the impl
 122   // thread to main.
 123   void SetNeedsCommit();
 124
 125   // As SetNeedsCommit(), but ensures the begin frame will be sent to the main
 126   // thread even if we are not visible.  After this call we expect to go through
 127   // the forced commit flow and then return to waiting for a non-forced
 128   // begin frame to finish.
 129   void SetNeedsForcedCommit();
 130
 131   // Call this only in response to receiving an
 132   // ACTION_SEND_BEGIN_FRAME_TO_MAIN_THREAD from NextAction.
 133   // Indicates that all painting is complete.
 134   void FinishCommit();
 135
 136   // Call this only in response to receiving an
 137   // ACTION_SEND_BEGIN_FRAME_TO_MAIN_THREAD from NextAction if the client
 138   // rejects the begin frame message.  If did_handle is false, then
 139   // another commit will be retried soon.
 140   void BeginFrameAbortedByMainThread(bool did_handle);
 141
 142   // Request exclusive access to the textures that back single buffered
 143   // layers on behalf of the main thread. Upon acquisition,
 144   // ACTION_DRAW_IF_POSSIBLE will not draw until the main thread releases the
 145   // textures to the impl thread by committing the layers.
 146   void SetMainThreadNeedsLayerTextures();
 147
 148   // Set that we can create the first OutputSurface and start the scheduler.
 149   void SetCanStart() { can_start_ = true; }
 150
 151   // Indicates whether drawing would, at this time, make sense.
 152   // CanDraw can be used to supress flashes or checkerboarding
 153   // when such behavior would be undesirable.
 154   void SetCanDraw(bool can);
 155
 156   // Indicates that the pending tree is ready for activation.
 157   void NotifyReadyToActivate();
 158
 159   bool has_pending_tree() const { return has_pending_tree_; }
 160
 161   void DidLoseOutputSurface();
 162   void DidCreateAndInitializeOutputSurface();
 163   bool HasInitializedOutputSurface() const;
 164
 165   // Exposed for testing purposes.
 166   void SetMaximumNumberOfFailedDrawsBeforeDrawIsForced(int num_draws);
 167
 168   // True if we need to abort draws to make forward progress.
 169   bool PendingDrawsShouldBeAborted() const;
 170
 171  protected:
 172   // True if we need to force activations to make forward progress.
 173   bool PendingActivationsShouldBeForced() const;
 174
 175   bool ShouldBeginOutputSurfaceCreation() const;
 176   bool ShouldDrawForced() const;
 177   bool ShouldDraw() const;
 178   bool ShouldActivatePendingTree() const;
 179   bool ShouldAcquireLayerTexturesForMainThread() const;
 180   bool ShouldUpdateVisibleTiles() const;
 181   bool ShouldSendBeginFrameToMainThread() const;
 182   bool ShouldCommit() const;
 183
 184   bool HasDrawnThisFrame() const;
 185   bool HasActivatedPendingTreeThisFrame() const;
 186   bool HasUpdatedVisibleTilesThisFrame() const;
 187   bool HasSentBeginFrameToMainThreadThisFrame() const;
 188
 189   void UpdateStateOnCommit(bool commit_was_aborted);
 190   void UpdateStateOnActivation();
 191   void UpdateStateOnDraw(bool did_swap);
 192
 193   const SchedulerSettings settings_;
 194
 195   OutputSurfaceState output_surface_state_;
 196   CommitState commit_state_;
 197
 198   int commit_count_;
 199   int current_frame_number_;
 200   int last_frame_number_where_begin_frame_sent_to_main_thread_;
 201   int last_frame_number_where_draw_was_called_;
 202   int last_frame_number_where_update_visible_tiles_was_called_;
 203   int consecutive_failed_draws_;
 204   int maximum_number_of_failed_draws_before_draw_is_forced_;
 205   bool needs_redraw_;
 206   bool swap_used_incomplete_tile_;
 207   bool needs_forced_redraw_;
 208   bool needs_forced_redraw_after_next_commit_;
 209   bool needs_commit_;
 210   bool needs_forced_commit_;
 211   bool expect_immediate_begin_frame_for_main_thread_;
 212   bool main_thread_needs_layer_textures_;
 213   bool inside_begin_frame_;
 214   BeginFrameArgs last_begin_frame_args_;
 215   bool visible_;
 216   bool can_start_;
 217   bool can_draw_;
 218   bool has_pending_tree_;
 219   bool pending_tree_is_ready_for_activation_;
 220   bool active_tree_has_been_drawn_;
 221   bool draw_if_possible_failed_;
 222   TextureState texture_state_;
 223   bool did_create_and_initialize_first_output_surface_;
 224
 225  private:
 226   DISALLOW_COPY_AND_ASSIGN(SchedulerStateMachine);
 227 };
 228
 229 }  // namespace cc
 230
 231 #endif  // CC_SCHEDULER_SCHEDULER_STATE_MACHINE_H_