src/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   // Note: BeginImplFrameState will always cycle through all the states in
  49   // order. Whether or not it actually waits or draws, it will at least try to
  50   // wait in BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME and try to draw in
  51   // BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE
  52   enum BeginImplFrameState {
  53     BEGIN_IMPL_FRAME_STATE_IDLE,
  54     BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING,
  55     BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME,
  56     BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE,
  57   };
  58   static const char* BeginImplFrameStateToString(BeginImplFrameState state);
  59
  60   enum CommitState {
  61     COMMIT_STATE_IDLE,
  62     COMMIT_STATE_FRAME_IN_PROGRESS,
  63     COMMIT_STATE_READY_TO_COMMIT,
  64     COMMIT_STATE_WAITING_FOR_FIRST_DRAW,
  65   };
  66   static const char* CommitStateToString(CommitState state);
  67
  68   enum TextureState {
  69     LAYER_TEXTURE_STATE_UNLOCKED,
  70     LAYER_TEXTURE_STATE_ACQUIRED_BY_MAIN_THREAD,
  71     LAYER_TEXTURE_STATE_ACQUIRED_BY_IMPL_THREAD,
  72   };
  73   static const char* TextureStateToString(TextureState state);
  74
  75   enum SynchronousReadbackState {
  76     READBACK_STATE_IDLE,
  77     READBACK_STATE_NEEDS_BEGIN_MAIN_FRAME,
  78     READBACK_STATE_WAITING_FOR_COMMIT,
  79     READBACK_STATE_WAITING_FOR_ACTIVATION,
  80     READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK,
  81     READBACK_STATE_WAITING_FOR_REPLACEMENT_COMMIT,
  82     READBACK_STATE_WAITING_FOR_REPLACEMENT_ACTIVATION,
  83   };
  84   static const char* SynchronousReadbackStateToString(
  85       SynchronousReadbackState state);
  86
  87   enum ForcedRedrawOnTimeoutState {
  88     FORCED_REDRAW_STATE_IDLE,
  89     FORCED_REDRAW_STATE_WAITING_FOR_COMMIT,
  90     FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION,
  91     FORCED_REDRAW_STATE_WAITING_FOR_DRAW,
  92   };
  93   static const char* ForcedRedrawOnTimeoutStateToString(
  94       ForcedRedrawOnTimeoutState state);
  95
  96   bool CommitPending() const {
  97     return commit_state_ == COMMIT_STATE_FRAME_IN_PROGRESS ||
  98            commit_state_ == COMMIT_STATE_READY_TO_COMMIT;
  99   }
 100
 101   bool RedrawPending() const { return needs_redraw_; }
 102   bool ManageTilesPending() const { return needs_manage_tiles_; }
 103
 104   enum Action {
 105     ACTION_NONE,
 106     ACTION_SEND_BEGIN_MAIN_FRAME,
 107     ACTION_COMMIT,
 108     ACTION_UPDATE_VISIBLE_TILES,
 109     ACTION_ACTIVATE_PENDING_TREE,
 110     ACTION_DRAW_AND_SWAP_IF_POSSIBLE,
 111     ACTION_DRAW_AND_SWAP_FORCED,
 112     ACTION_DRAW_AND_SWAP_ABORT,
 113     ACTION_DRAW_AND_READBACK,
 114     ACTION_BEGIN_OUTPUT_SURFACE_CREATION,
 115     ACTION_ACQUIRE_LAYER_TEXTURES_FOR_MAIN_THREAD,
 116     ACTION_MANAGE_TILES,
 117   };
 118   static const char* ActionToString(Action action);
 119
 120   scoped_ptr<base::Value> AsValue() const;
 121
 122   Action NextAction() const;
 123   void UpdateState(Action action);
 124
 125   void CheckInvariants();
 126
 127   // Indicates whether the impl thread needs a BeginImplFrame callback in order
 128   // to make progress.
 129   bool BeginImplFrameNeeded() const;
 130
 131   // Indicates that we need to independently poll for new state and actions
 132   // because we can't expect a BeginImplFrame. This is mostly used to avoid
 133   // drawing repeat frames with the synchronous compositor without dropping
 134   // necessary actions on the floor.
 135   bool ShouldPollForAnticipatedDrawTriggers() const;
 136
 137   // Indicates that the system has entered and left a BeginImplFrame callback.
 138   // The scheduler will not draw more than once in a given BeginImplFrame
 139   // callback nor send more than one BeginMainFrame message.
 140   void OnBeginImplFrame(const BeginFrameArgs& args);
 141   void OnBeginImplFrameDeadlinePending();
 142   void OnBeginImplFrameDeadline();
 143   void OnBeginImplFrameIdle();
 144   bool ShouldTriggerBeginImplFrameDeadlineEarly() const;
 145   BeginImplFrameState begin_impl_frame_state() const {
 146     return begin_impl_frame_state_;
 147   }
 148
 149   // PollForAnticipatedDrawTriggers is used by the synchronous compositor to
 150   // avoid requesting BeginImplFrames when we won't actually draw but still
 151   // need to advance our state at vsync intervals.
 152   void DidEnterPollForAnticipatedDrawTriggers();
 153   void DidLeavePollForAnticipatedDrawTriggers();
 154   bool inside_poll_for_anticipated_draw_triggers() const {
 155     return inside_poll_for_anticipated_draw_triggers_;
 156   }
 157
 158   // Indicates whether the LayerTreeHostImpl is visible.
 159   void SetVisible(bool visible);
 160
 161   // Indicates that a redraw is required, either due to the impl tree changing
 162   // or the screen being damaged and simply needing redisplay.
 163   void SetNeedsRedraw();
 164   bool needs_redraw() const { return needs_redraw_; }
 165
 166   // Indicates that manage-tiles is required. This guarantees another
 167   // ManageTiles will occur shortly (even if no redraw is required).
 168   void SetNeedsManageTiles();
 169
 170   // Indicates whether a redraw is required because we are currently rendering
 171   // with a low resolution or checkerboarded tile.
 172   void SetSwapUsedIncompleteTile(bool used_incomplete_tile);
 173
 174   // Indicates whether to prioritize animation smoothness over new content
 175   // activation.
 176   void SetSmoothnessTakesPriority(bool smoothness_takes_priority);
 177
 178   // Indicates whether ACTION_DRAW_AND_SWAP_IF_POSSIBLE drew to the screen.
 179   void DidDrawIfPossibleCompleted(bool success);
 180
 181   // Indicates that a new commit flow needs to be performed, either to pull
 182   // updates from the main thread to the impl, or to push deltas from the impl
 183   // thread to main.
 184   void SetNeedsCommit();
 185
 186   // As SetNeedsCommit(), but ensures the BeginMainFrame will be sent even
 187   // if we are not visible.  After this call we expect to go through
 188   // the forced commit flow and then return to waiting for a non-forced
 189   // BeginMainFrame to finish.
 190   void SetNeedsForcedCommitForReadback();
 191
 192   // Call this only in response to receiving an ACTION_SEND_BEGIN_MAIN_FRAME
 193   // from NextAction.
 194   // Indicates that all painting is complete.
 195   void FinishCommit();
 196
 197   // Call this only in response to receiving an ACTION_SEND_BEGIN_MAIN_FRAME
 198   // from NextAction if the client rejects the BeginMainFrame message.
 199   // If did_handle is false, then another commit will be retried soon.
 200   void BeginMainFrameAborted(bool did_handle);
 201
 202   // Request exclusive access to the textures that back single buffered
 203   // layers on behalf of the main thread. Upon acquisition,
 204   // ACTION_DRAW_AND_SWAP_IF_POSSIBLE will not draw until the main thread
 205   // releases the
 206   // textures to the impl thread by committing the layers.
 207   void SetMainThreadNeedsLayerTextures();
 208
 209   // Set that we can create the first OutputSurface and start the scheduler.
 210   void SetCanStart() { can_start_ = true; }
 211
 212   // Indicates whether drawing would, at this time, make sense.
 213   // CanDraw can be used to suppress flashes or checkerboarding
 214   // when such behavior would be undesirable.
 215   void SetCanDraw(bool can);
 216
 217   // Indicates that the pending tree is ready for activation.
 218   void NotifyReadyToActivate();
 219
 220   bool has_pending_tree() const { return has_pending_tree_; }
 221
 222   void DidLoseOutputSurface();
 223   void DidCreateAndInitializeOutputSurface();
 224   bool HasInitializedOutputSurface() const;
 225
 226   // True if we need to abort draws to make forward progress.
 227   bool PendingDrawsShouldBeAborted() const;
 228
 229   bool SupportsProactiveBeginImplFrame() const;
 230
 231  protected:
 232   bool BeginImplFrameNeededToDraw() const;
 233   bool ProactiveBeginImplFrameWanted() const;
 234
 235   // True if we need to force activations to make forward progress.
 236   bool PendingActivationsShouldBeForced() const;
 237
 238   bool ShouldBeginOutputSurfaceCreation() const;
 239   bool ShouldDrawForced() const;
 240   bool ShouldDraw() const;
 241   bool ShouldActivatePendingTree() const;
 242   bool ShouldAcquireLayerTexturesForMainThread() const;
 243   bool ShouldUpdateVisibleTiles() const;
 244   bool ShouldSendBeginMainFrame() const;
 245   bool ShouldCommit() const;
 246   bool ShouldManageTiles() const;
 247
 248   bool HasSentBeginMainFrameThisFrame() const;
 249   bool HasScheduledManageTilesThisFrame() const;
 250   bool HasUpdatedVisibleTilesThisFrame() const;
 251   bool HasSwappedThisFrame() const;
 252
 253   void UpdateStateOnCommit(bool commit_was_aborted);
 254   void UpdateStateOnActivation();
 255   void UpdateStateOnDraw(bool did_swap);
 256   void UpdateStateOnManageTiles();
 257
 258   const SchedulerSettings settings_;
 259
 260   OutputSurfaceState output_surface_state_;
 261   BeginImplFrameState begin_impl_frame_state_;
 262   CommitState commit_state_;
 263   TextureState texture_state_;
 264   ForcedRedrawOnTimeoutState forced_redraw_state_;
 265   SynchronousReadbackState readback_state_;
 266
 267   BeginFrameArgs last_begin_impl_frame_args_;
 268
 269   int commit_count_;
 270   int current_frame_number_;
 271   int last_frame_number_swap_performed_;
 272   int last_frame_number_begin_main_frame_sent_;
 273   int last_frame_number_update_visible_tiles_was_called_;
 274
 275   int consecutive_failed_draws_;
 276   bool needs_redraw_;
 277   bool needs_manage_tiles_;
 278   bool swap_used_incomplete_tile_;
 279   bool needs_commit_;
 280   bool main_thread_needs_layer_textures_;
 281   bool inside_poll_for_anticipated_draw_triggers_;
 282   bool visible_;
 283   bool can_start_;
 284   bool can_draw_;
 285   bool has_pending_tree_;
 286   bool pending_tree_is_ready_for_activation_;
 287   bool active_tree_needs_first_draw_;
 288   bool draw_if_possible_failed_;
 289   bool did_create_and_initialize_first_output_surface_;
 290   bool smoothness_takes_priority_;
 291
 292  private:
 293   DISALLOW_COPY_AND_ASSIGN(SchedulerStateMachine);
 294 };
 295
 296 }  // namespace cc
 297
 298 #endif  // CC_SCHEDULER_SCHEDULER_STATE_MACHINE_H_