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/draw_result.h"
  16 #include "cc/scheduler/scheduler_settings.h"
  17
  18 namespace base {
  19 namespace debug {
  20 class ConvertableToTraceFormat;
  21 class TracedValue;
  22 }
  23 class Value;
  24 }
  25
  26 namespace cc {
  27
  28 // The SchedulerStateMachine decides how to coordinate main thread activites
  29 // like painting/running javascript with rendering and input activities on the
  30 // impl thread.
  31 //
  32 // The state machine tracks internal state but is also influenced by external
  33 // state.  Internal state includes things like whether a frame has been
  34 // requested, while external state includes things like the current time being
  35 // near to the vblank time.
  36 //
  37 // The scheduler seperates "what to do next" from the updating of its internal
  38 // state to make testing cleaner.
  39 class CC_EXPORT SchedulerStateMachine {
  40  public:
  41   // settings must be valid for the lifetime of this class.
  42   explicit SchedulerStateMachine(const SchedulerSettings& settings);
  43
  44   enum OutputSurfaceState {
  45     OUTPUT_SURFACE_ACTIVE,
  46     OUTPUT_SURFACE_LOST,
  47     OUTPUT_SURFACE_CREATING,
  48     OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT,
  49     OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION,
  50   };
  51   static const char* OutputSurfaceStateToString(OutputSurfaceState state);
  52
  53   // Note: BeginImplFrameState will always cycle through all the states in
  54   // order. Whether or not it actually waits or draws, it will at least try to
  55   // wait in BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME and try to draw in
  56   // BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE
  57   enum BeginImplFrameState {
  58     BEGIN_IMPL_FRAME_STATE_IDLE,
  59     BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING,
  60     BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME,
  61     BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE,
  62   };
  63   static const char* BeginImplFrameStateToString(BeginImplFrameState state);
  64
  65   enum CommitState {
  66     COMMIT_STATE_IDLE,
  67     COMMIT_STATE_BEGIN_MAIN_FRAME_SENT,
  68     COMMIT_STATE_BEGIN_MAIN_FRAME_STARTED,
  69     COMMIT_STATE_READY_TO_COMMIT,
  70     COMMIT_STATE_WAITING_FOR_ACTIVATION,
  71   };
  72   static const char* CommitStateToString(CommitState state);
  73
  74   enum ForcedRedrawOnTimeoutState {
  75     FORCED_REDRAW_STATE_IDLE,
  76     FORCED_REDRAW_STATE_WAITING_FOR_COMMIT,
  77     FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION,
  78     FORCED_REDRAW_STATE_WAITING_FOR_DRAW,
  79   };
  80   static const char* ForcedRedrawOnTimeoutStateToString(
  81       ForcedRedrawOnTimeoutState state);
  82
  83   bool CommitPending() const {
  84     return commit_state_ == COMMIT_STATE_BEGIN_MAIN_FRAME_SENT ||
  85            commit_state_ == COMMIT_STATE_BEGIN_MAIN_FRAME_STARTED ||
  86            commit_state_ == COMMIT_STATE_READY_TO_COMMIT;
  87   }
  88   CommitState commit_state() const { return commit_state_; }
  89
  90   bool RedrawPending() const { return needs_redraw_; }
  91   bool ManageTilesPending() const { return needs_manage_tiles_; }
  92
  93   enum Action {
  94     ACTION_NONE,
  95     ACTION_ANIMATE,
  96     ACTION_SEND_BEGIN_MAIN_FRAME,
  97     ACTION_COMMIT,
  98     ACTION_UPDATE_VISIBLE_TILES,
  99     ACTION_ACTIVATE_SYNC_TREE,
 100     ACTION_DRAW_AND_SWAP_IF_POSSIBLE,
 101     ACTION_DRAW_AND_SWAP_FORCED,
 102     ACTION_DRAW_AND_SWAP_ABORT,
 103     ACTION_BEGIN_OUTPUT_SURFACE_CREATION,
 104     ACTION_MANAGE_TILES,
 105   };
 106   static const char* ActionToString(Action action);
 107
 108   scoped_refptr<base::debug::ConvertableToTraceFormat> AsValue() const;
 109   void AsValueInto(base::debug::TracedValue* dict, base::TimeTicks now) const;
 110
 111   Action NextAction() const;
 112   void UpdateState(Action action);
 113
 114   // Indicates whether the impl thread needs a BeginImplFrame callback in order
 115   // to make progress.
 116   bool BeginFrameNeeded() const;
 117
 118   // Indicates that we need to independently poll for new state and actions
 119   // because we can't expect a BeginImplFrame. This is mostly used to avoid
 120   // drawing repeat frames with the synchronous compositor without dropping
 121   // necessary actions on the floor.
 122   bool ShouldPollForAnticipatedDrawTriggers() const;
 123
 124   // Indicates that the system has entered and left a BeginImplFrame callback.
 125   // The scheduler will not draw more than once in a given BeginImplFrame
 126   // callback nor send more than one BeginMainFrame message.
 127   void OnBeginImplFrame(const BeginFrameArgs& args);
 128   void OnBeginImplFrameDeadlinePending();
 129   void OnBeginImplFrameDeadline();
 130   void OnBeginImplFrameIdle();
 131   bool ShouldTriggerBeginImplFrameDeadlineEarly() const;
 132   BeginImplFrameState begin_impl_frame_state() const {
 133     return begin_impl_frame_state_;
 134   }
 135
 136   // If the main thread didn't manage to produce a new frame in time for the
 137   // impl thread to draw, it is in a high latency mode.
 138   bool MainThreadIsInHighLatencyMode() const;
 139
 140   // PollForAnticipatedDrawTriggers is used by the synchronous compositor to
 141   // avoid requesting BeginImplFrames when we won't actually draw but still
 142   // need to advance our state at vsync intervals.
 143   void DidEnterPollForAnticipatedDrawTriggers();
 144   void DidLeavePollForAnticipatedDrawTriggers();
 145   bool inside_poll_for_anticipated_draw_triggers() const {
 146     return inside_poll_for_anticipated_draw_triggers_;
 147   }
 148
 149   // Indicates whether the LayerTreeHostImpl is visible.
 150   void SetVisible(bool visible);
 151
 152   // Indicates that a redraw is required, either due to the impl tree changing
 153   // or the screen being damaged and simply needing redisplay.
 154   void SetNeedsRedraw();
 155   bool needs_redraw() const { return needs_redraw_; }
 156
 157   void SetNeedsAnimate();
 158   bool needs_animate() const { return needs_animate_; }
 159
 160   // Indicates that manage-tiles is required. This guarantees another
 161   // ManageTiles will occur shortly (even if no redraw is required).
 162   void SetNeedsManageTiles();
 163
 164   // Sets how many swaps can be pending to the OutputSurface.
 165   void SetMaxSwapsPending(int max);
 166
 167   // If the scheduler attempted to draw and swap, this provides feedback
 168   // regarding whether or not the swap actually occured. We might skip the
 169   // swap when there is not damage, for example.
 170   void DidSwapBuffers();
 171
 172   // Indicates whether a redraw is required because we are currently rendering
 173   // with a low resolution or checkerboarded tile.
 174   void SetSwapUsedIncompleteTile(bool used_incomplete_tile);
 175
 176   // Notification from the OutputSurface that a swap has been consumed.
 177   void DidSwapBuffersComplete();
 178
 179   // Indicates whether to prioritize impl thread latency (i.e., animation
 180   // smoothness) over new content activation.
 181   void SetImplLatencyTakesPriority(bool impl_latency_takes_priority);
 182   bool impl_latency_takes_priority() const {
 183     return impl_latency_takes_priority_;
 184   }
 185
 186   // Indicates whether ACTION_DRAW_AND_SWAP_IF_POSSIBLE drew to the screen.
 187   void DidDrawIfPossibleCompleted(DrawResult result);
 188
 189   // Indicates that a new commit flow needs to be performed, either to pull
 190   // updates from the main thread to the impl, or to push deltas from the impl
 191   // thread to main.
 192   void SetNeedsCommit();
 193
 194   // Call this only in response to receiving an ACTION_SEND_BEGIN_MAIN_FRAME
 195   // from NextAction.
 196   // Indicates that all painting is complete.
 197   void NotifyReadyToCommit();
 198
 199   // Call this only in response to receiving an ACTION_SEND_BEGIN_MAIN_FRAME
 200   // from NextAction if the client rejects the BeginMainFrame message.
 201   // If did_handle is false, then another commit will be retried soon.
 202   void BeginMainFrameAborted(bool did_handle);
 203
 204   // Set that we can create the first OutputSurface and start the scheduler.
 205   void SetCanStart() { can_start_ = true; }
 206
 207   void SetSkipNextBeginMainFrameToReduceLatency();
 208
 209   // Indicates whether drawing would, at this time, make sense.
 210   // CanDraw can be used to suppress flashes or checkerboarding
 211   // when such behavior would be undesirable.
 212   void SetCanDraw(bool can);
 213
 214   // Indicates that scheduled BeginMainFrame is started.
 215   void NotifyBeginMainFrameStarted();
 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   bool active_tree_needs_first_draw() const {
 222     return active_tree_needs_first_draw_;
 223   }
 224
 225   void DidManageTiles();
 226   void DidLoseOutputSurface();
 227   void DidCreateAndInitializeOutputSurface();
 228   bool HasInitializedOutputSurface() const;
 229
 230   // True if we need to abort draws to make forward progress.
 231   bool PendingDrawsShouldBeAborted() const;
 232
 233   bool SupportsProactiveBeginFrame() const;
 234
 235   void SetContinuousPainting(bool continuous_painting) {
 236     continuous_painting_ = continuous_painting;
 237   }
 238
 239   bool CouldSendBeginMainFrame() const;
 240
 241   void SetImplLatencyTakesPriorityOnBattery(
 242       bool impl_latency_takes_priority_on_battery) {
 243     impl_latency_takes_priority_on_battery_ =
 244         impl_latency_takes_priority_on_battery;
 245   }
 246
 247   // TODO(zmo): This is temporary for debugging crbug.com/393331.
 248   // We should remove it afterwards.
 249   std::string GetStatesForDebugging() const;
 250
 251  protected:
 252   bool BeginFrameNeededToAnimateOrDraw() const;
 253   bool ProactiveBeginFrameWanted() const;
 254
 255   // True if we need to force activations to make forward progress.
 256   bool PendingActivationsShouldBeForced() const;
 257
 258   bool ShouldAnimate() const;
 259   bool ShouldBeginOutputSurfaceCreation() const;
 260   bool ShouldDrawForced() const;
 261   bool ShouldDraw() const;
 262   bool ShouldActivatePendingTree() const;
 263   bool ShouldUpdateVisibleTiles() const;
 264   bool ShouldSendBeginMainFrame() const;
 265   bool ShouldCommit() const;
 266   bool ShouldManageTiles() const;
 267
 268   void AdvanceCurrentFrameNumber();
 269   bool HasAnimatedThisFrame() const;
 270   bool HasSentBeginMainFrameThisFrame() const;
 271   bool HasUpdatedVisibleTilesThisFrame() const;
 272   bool HasRequestedSwapThisFrame() const;
 273   bool HasSwappedThisFrame() const;
 274
 275   void UpdateStateOnCommit(bool commit_was_aborted);
 276   void UpdateStateOnActivation();
 277   void UpdateStateOnDraw(bool did_request_swap);
 278   void UpdateStateOnManageTiles();
 279
 280   const SchedulerSettings settings_;
 281
 282   OutputSurfaceState output_surface_state_;
 283   BeginImplFrameState begin_impl_frame_state_;
 284   CommitState commit_state_;
 285   ForcedRedrawOnTimeoutState forced_redraw_state_;
 286
 287   BeginFrameArgs begin_impl_frame_args_;
 288
 289   int commit_count_;
 290   int current_frame_number_;
 291   int last_frame_number_animate_performed_;
 292   int last_frame_number_swap_performed_;
 293   int last_frame_number_swap_requested_;
 294   int last_frame_number_begin_main_frame_sent_;
 295   int last_frame_number_update_visible_tiles_was_called_;
 296
 297   // manage_tiles_funnel_ is "filled" each time ManageTiles is called
 298   // and "drained" on each BeginImplFrame. If the funnel gets too full,
 299   // we start throttling ACTION_MANAGE_TILES such that we average one
 300   // ManageTile per BeginImplFrame.
 301   int manage_tiles_funnel_;
 302   int consecutive_checkerboard_animations_;
 303   int max_pending_swaps_;
 304   int pending_swaps_;
 305   bool needs_redraw_;
 306   bool needs_animate_;
 307   bool needs_manage_tiles_;
 308   bool swap_used_incomplete_tile_;
 309   bool needs_commit_;
 310   bool inside_poll_for_anticipated_draw_triggers_;
 311   bool visible_;
 312   bool can_start_;
 313   bool can_draw_;
 314   bool has_pending_tree_;
 315   bool pending_tree_is_ready_for_activation_;
 316   bool active_tree_needs_first_draw_;
 317   bool did_commit_after_animating_;
 318   bool did_create_and_initialize_first_output_surface_;
 319   bool impl_latency_takes_priority_;
 320   bool skip_next_begin_main_frame_to_reduce_latency_;
 321   bool skip_begin_main_frame_to_reduce_latency_;
 322   bool continuous_painting_;
 323   bool impl_latency_takes_priority_on_battery_;
 324
 325  private:
 326   DISALLOW_COPY_AND_ASSIGN(SchedulerStateMachine);
 327 };
 328
 329 }  // namespace cc
 330
 331 #endif  // CC_SCHEDULER_SCHEDULER_STATE_MACHINE_H_