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_ACTIVATE_SYNC_TREE,
  99     ACTION_DRAW_AND_SWAP_IF_POSSIBLE,
 100     ACTION_DRAW_AND_SWAP_FORCED,
 101     ACTION_DRAW_AND_SWAP_ABORT,
 102     ACTION_BEGIN_OUTPUT_SURFACE_CREATION,
 103     ACTION_MANAGE_TILES,
 104   };
 105   static const char* ActionToString(Action action);
 106
 107   scoped_refptr<base::debug::ConvertableToTraceFormat> AsValue() const;
 108   void AsValueInto(base::debug::TracedValue* dict, base::TimeTicks now) const;
 109
 110   Action NextAction() const;
 111   void UpdateState(Action action);
 112
 113   // Indicates whether the impl thread needs a BeginImplFrame callback in order
 114   // to make progress.
 115   bool BeginFrameNeeded() const;
 116
 117   // Indicates that we need to independently poll for new state and actions
 118   // because we can't expect a BeginImplFrame. This is mostly used to avoid
 119   // drawing repeat frames with the synchronous compositor without dropping
 120   // necessary actions on the floor.
 121   bool ShouldPollForAnticipatedDrawTriggers() const;
 122
 123   // Indicates that the system has entered and left a BeginImplFrame callback.
 124   // The scheduler will not draw more than once in a given BeginImplFrame
 125   // callback nor send more than one BeginMainFrame message.
 126   void OnBeginImplFrame(const BeginFrameArgs& args);
 127   void OnBeginImplFrameDeadlinePending();
 128   void OnBeginImplFrameDeadline();
 129   void OnBeginImplFrameIdle();
 130   bool ShouldTriggerBeginImplFrameDeadlineEarly() const;
 131   BeginImplFrameState begin_impl_frame_state() const {
 132     return begin_impl_frame_state_;
 133   }
 134
 135   // If the main thread didn't manage to produce a new frame in time for the
 136   // impl thread to draw, it is in a high latency mode.
 137   bool MainThreadIsInHighLatencyMode() const;
 138
 139   // PollForAnticipatedDrawTriggers is used by the synchronous compositor to
 140   // avoid requesting BeginImplFrames when we won't actually draw but still
 141   // need to advance our state at vsync intervals.
 142   void DidEnterPollForAnticipatedDrawTriggers();
 143   void DidLeavePollForAnticipatedDrawTriggers();
 144   bool inside_poll_for_anticipated_draw_triggers() const {
 145     return inside_poll_for_anticipated_draw_triggers_;
 146   }
 147
 148   // Indicates whether the LayerTreeHostImpl is visible.
 149   void SetVisible(bool visible);
 150
 151   // Indicates that a redraw is required, either due to the impl tree changing
 152   // or the screen being damaged and simply needing redisplay.
 153   void SetNeedsRedraw();
 154   bool needs_redraw() const { return needs_redraw_; }
 155
 156   void SetNeedsAnimate();
 157   bool needs_animate() const { return needs_animate_; }
 158
 159   // Indicates that manage-tiles is required. This guarantees another
 160   // ManageTiles will occur shortly (even if no redraw is required).
 161   void SetNeedsManageTiles();
 162
 163   // Sets how many swaps can be pending to the OutputSurface.
 164   void SetMaxSwapsPending(int max);
 165
 166   // If the scheduler attempted to draw and swap, this provides feedback
 167   // regarding whether or not the swap actually occured. We might skip the
 168   // swap when there is not damage, for example.
 169   void DidSwapBuffers();
 170
 171   // Indicates whether a redraw is required because we are currently rendering
 172   // with a low resolution or checkerboarded tile.
 173   void SetSwapUsedIncompleteTile(bool used_incomplete_tile);
 174
 175   // Notification from the OutputSurface that a swap has been consumed.
 176   void DidSwapBuffersComplete();
 177
 178   // Indicates whether to prioritize impl thread latency (i.e., animation
 179   // smoothness) over new content activation.
 180   void SetImplLatencyTakesPriority(bool impl_latency_takes_priority);
 181   bool impl_latency_takes_priority() const {
 182     return impl_latency_takes_priority_;
 183   }
 184
 185   // Indicates whether ACTION_DRAW_AND_SWAP_IF_POSSIBLE drew to the screen.
 186   void DidDrawIfPossibleCompleted(DrawResult result);
 187
 188   // Indicates that a new commit flow needs to be performed, either to pull
 189   // updates from the main thread to the impl, or to push deltas from the impl
 190   // thread to main.
 191   void SetNeedsCommit();
 192
 193   // Call this only in response to receiving an ACTION_SEND_BEGIN_MAIN_FRAME
 194   // from NextAction.
 195   // Indicates that all painting is complete.
 196   void NotifyReadyToCommit();
 197
 198   // Call this only in response to receiving an ACTION_SEND_BEGIN_MAIN_FRAME
 199   // from NextAction if the client rejects the BeginMainFrame message.
 200   // If did_handle is false, then another commit will be retried soon.
 201   void BeginMainFrameAborted(bool did_handle);
 202
 203   // Set that we can create the first OutputSurface and start the scheduler.
 204   void SetCanStart() { can_start_ = true; }
 205
 206   void SetSkipNextBeginMainFrameToReduceLatency();
 207
 208   // Indicates whether drawing would, at this time, make sense.
 209   // CanDraw can be used to suppress flashes or checkerboarding
 210   // when such behavior would be undesirable.
 211   void SetCanDraw(bool can);
 212
 213   // Indicates that scheduled BeginMainFrame is started.
 214   void NotifyBeginMainFrameStarted();
 215
 216   // Indicates that the pending tree is ready for activation.
 217   void NotifyReadyToActivate();
 218
 219   bool has_pending_tree() const { return has_pending_tree_; }
 220   bool active_tree_needs_first_draw() const {
 221     return active_tree_needs_first_draw_;
 222   }
 223
 224   void DidManageTiles();
 225   void DidLoseOutputSurface();
 226   void DidCreateAndInitializeOutputSurface();
 227   bool HasInitializedOutputSurface() const;
 228
 229   // True if we need to abort draws to make forward progress.
 230   bool PendingDrawsShouldBeAborted() const;
 231
 232   bool SupportsProactiveBeginFrame() const;
 233
 234   void SetContinuousPainting(bool continuous_painting) {
 235     continuous_painting_ = continuous_painting;
 236   }
 237
 238   bool CouldSendBeginMainFrame() const;
 239
 240   void SetImplLatencyTakesPriorityOnBattery(
 241       bool impl_latency_takes_priority_on_battery) {
 242     impl_latency_takes_priority_on_battery_ =
 243         impl_latency_takes_priority_on_battery;
 244   }
 245
 246   // TODO(zmo): This is temporary for debugging crbug.com/393331.
 247   // We should remove it afterwards.
 248   std::string GetStatesForDebugging() const;
 249
 250  protected:
 251   bool BeginFrameNeededToAnimateOrDraw() const;
 252   bool ProactiveBeginFrameWanted() const;
 253
 254   // True if we need to force activations to make forward progress.
 255   bool PendingActivationsShouldBeForced() const;
 256
 257   bool ShouldAnimate() const;
 258   bool ShouldBeginOutputSurfaceCreation() const;
 259   bool ShouldDrawForced() const;
 260   bool ShouldDraw() const;
 261   bool ShouldActivatePendingTree() const;
 262   bool ShouldSendBeginMainFrame() const;
 263   bool ShouldCommit() const;
 264   bool ShouldManageTiles() const;
 265
 266   void AdvanceCurrentFrameNumber();
 267   bool HasAnimatedThisFrame() const;
 268   bool HasSentBeginMainFrameThisFrame() const;
 269   bool HasRequestedSwapThisFrame() const;
 270   bool HasSwappedThisFrame() const;
 271
 272   void UpdateStateOnCommit(bool commit_was_aborted);
 273   void UpdateStateOnActivation();
 274   void UpdateStateOnDraw(bool did_request_swap);
 275   void UpdateStateOnManageTiles();
 276
 277   const SchedulerSettings settings_;
 278
 279   OutputSurfaceState output_surface_state_;
 280   BeginImplFrameState begin_impl_frame_state_;
 281   CommitState commit_state_;
 282   ForcedRedrawOnTimeoutState forced_redraw_state_;
 283
 284   BeginFrameArgs begin_impl_frame_args_;
 285
 286   int commit_count_;
 287   int current_frame_number_;
 288   int last_frame_number_animate_performed_;
 289   int last_frame_number_swap_performed_;
 290   int last_frame_number_swap_requested_;
 291   int last_frame_number_begin_main_frame_sent_;
 292
 293   // manage_tiles_funnel_ is "filled" each time ManageTiles is called
 294   // and "drained" on each BeginImplFrame. If the funnel gets too full,
 295   // we start throttling ACTION_MANAGE_TILES such that we average one
 296   // ManageTile per BeginImplFrame.
 297   int manage_tiles_funnel_;
 298   int consecutive_checkerboard_animations_;
 299   int max_pending_swaps_;
 300   int pending_swaps_;
 301   bool needs_redraw_;
 302   bool needs_animate_;
 303   bool needs_manage_tiles_;
 304   bool needs_commit_;
 305   bool inside_poll_for_anticipated_draw_triggers_;
 306   bool visible_;
 307   bool can_start_;
 308   bool can_draw_;
 309   bool has_pending_tree_;
 310   bool pending_tree_is_ready_for_activation_;
 311   bool active_tree_needs_first_draw_;
 312   bool did_commit_after_animating_;
 313   bool did_create_and_initialize_first_output_surface_;
 314   bool impl_latency_takes_priority_;
 315   bool skip_next_begin_main_frame_to_reduce_latency_;
 316   bool skip_begin_main_frame_to_reduce_latency_;
 317   bool continuous_painting_;
 318   bool impl_latency_takes_priority_on_battery_;
 319
 320  private:
 321   DISALLOW_COPY_AND_ASSIGN(SchedulerStateMachine);
 322 };
 323
 324 }  // namespace cc
 325
 326 #endif  // CC_SCHEDULER_SCHEDULER_STATE_MACHINE_H_