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 ConvertableToTraceForamt;
  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     COMMIT_STATE_WAITING_FOR_FIRST_DRAW,
  72   };
  73   static const char* CommitStateToString(CommitState state);
  74
  75   enum ForcedRedrawOnTimeoutState {
  76     FORCED_REDRAW_STATE_IDLE,
  77     FORCED_REDRAW_STATE_WAITING_FOR_COMMIT,
  78     FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION,
  79     FORCED_REDRAW_STATE_WAITING_FOR_DRAW,
  80   };
  81   static const char* ForcedRedrawOnTimeoutStateToString(
  82       ForcedRedrawOnTimeoutState state);
  83
  84   bool CommitPending() const {
  85     return commit_state_ == COMMIT_STATE_BEGIN_MAIN_FRAME_SENT ||
  86            commit_state_ == COMMIT_STATE_BEGIN_MAIN_FRAME_STARTED ||
  87            commit_state_ == COMMIT_STATE_READY_TO_COMMIT;
  88   }
  89   CommitState commit_state() const { return commit_state_; }
  90
  91   bool RedrawPending() const { return needs_redraw_; }
  92   bool ManageTilesPending() const { return needs_manage_tiles_; }
  93
  94   enum Action {
  95     ACTION_NONE,
  96     ACTION_ANIMATE,
  97     ACTION_SEND_BEGIN_MAIN_FRAME,
  98     ACTION_COMMIT,
  99     ACTION_UPDATE_VISIBLE_TILES,
 100     ACTION_ACTIVATE_SYNC_TREE,
 101     ACTION_DRAW_AND_SWAP_IF_POSSIBLE,
 102     ACTION_DRAW_AND_SWAP_FORCED,
 103     ACTION_DRAW_AND_SWAP_ABORT,
 104     ACTION_BEGIN_OUTPUT_SURFACE_CREATION,
 105     ACTION_MANAGE_TILES,
 106   };
 107   static const char* ActionToString(Action action);
 108
 109   scoped_refptr<base::debug::ConvertableToTraceFormat> AsValue() const;
 110   void AsValueInto(base::debug::TracedValue* dict, base::TimeTicks now) const;
 111
 112   Action NextAction() const;
 113   void UpdateState(Action action);
 114
 115   // Indicates whether the impl thread needs a BeginImplFrame callback in order
 116   // to make progress.
 117   bool BeginFrameNeeded() const;
 118
 119   // Indicates that we need to independently poll for new state and actions
 120   // because we can't expect a BeginImplFrame. This is mostly used to avoid
 121   // drawing repeat frames with the synchronous compositor without dropping
 122   // necessary actions on the floor.
 123   bool ShouldPollForAnticipatedDrawTriggers() const;
 124
 125   // Indicates that the system has entered and left a BeginImplFrame callback.
 126   // The scheduler will not draw more than once in a given BeginImplFrame
 127   // callback nor send more than one BeginMainFrame message.
 128   void OnBeginImplFrame(const BeginFrameArgs& args);
 129   void OnBeginImplFrameDeadlinePending();
 130   void OnBeginImplFrameDeadline();
 131   void OnBeginImplFrameIdle();
 132   bool ShouldTriggerBeginImplFrameDeadlineEarly() const;
 133   BeginImplFrameState begin_impl_frame_state() const {
 134     return begin_impl_frame_state_;
 135   }
 136
 137   // If the main thread didn't manage to produce a new frame in time for the
 138   // impl thread to draw, it is in a high latency mode.
 139   bool MainThreadIsInHighLatencyMode() const;
 140
 141   // PollForAnticipatedDrawTriggers is used by the synchronous compositor to
 142   // avoid requesting BeginImplFrames when we won't actually draw but still
 143   // need to advance our state at vsync intervals.
 144   void DidEnterPollForAnticipatedDrawTriggers();
 145   void DidLeavePollForAnticipatedDrawTriggers();
 146   bool inside_poll_for_anticipated_draw_triggers() const {
 147     return inside_poll_for_anticipated_draw_triggers_;
 148   }
 149
 150   // Indicates whether the LayerTreeHostImpl is visible.
 151   void SetVisible(bool visible);
 152
 153   // Indicates that a redraw is required, either due to the impl tree changing
 154   // or the screen being damaged and simply needing redisplay.
 155   void SetNeedsRedraw();
 156   bool needs_redraw() const { return needs_redraw_; }
 157
 158   void SetNeedsAnimate();
 159   bool needs_animate() const { return needs_animate_; }
 160
 161   // Indicates that manage-tiles is required. This guarantees another
 162   // ManageTiles will occur shortly (even if no redraw is required).
 163   void SetNeedsManageTiles();
 164
 165   // Sets how many swaps can be pending to the OutputSurface.
 166   void SetMaxSwapsPending(int max);
 167
 168   // If the scheduler attempted to draw and swap, this provides feedback
 169   // regarding whether or not the swap actually occured. We might skip the
 170   // swap when there is not damage, for example.
 171   void DidSwapBuffers();
 172
 173   // Indicates whether a redraw is required because we are currently rendering
 174   // with a low resolution or checkerboarded tile.
 175   void SetSwapUsedIncompleteTile(bool used_incomplete_tile);
 176
 177   // Notification from the OutputSurface that a swap has been consumed.
 178   void DidSwapBuffersComplete();
 179
 180   // Indicates whether to prioritize impl thread latency (i.e., animation
 181   // smoothness) over new content activation.
 182   void SetImplLatencyTakesPriority(bool impl_latency_takes_priority);
 183   bool impl_latency_takes_priority() const {
 184     return impl_latency_takes_priority_;
 185   }
 186
 187   // Indicates whether ACTION_DRAW_AND_SWAP_IF_POSSIBLE drew to the screen.
 188   void DidDrawIfPossibleCompleted(DrawResult result);
 189
 190   // Indicates that a new commit flow needs to be performed, either to pull
 191   // updates from the main thread to the impl, or to push deltas from the impl
 192   // thread to main.
 193   void SetNeedsCommit();
 194
 195   // Call this only in response to receiving an ACTION_SEND_BEGIN_MAIN_FRAME
 196   // from NextAction.
 197   // Indicates that all painting is complete.
 198   void NotifyReadyToCommit();
 199
 200   // Call this only in response to receiving an ACTION_SEND_BEGIN_MAIN_FRAME
 201   // from NextAction if the client rejects the BeginMainFrame message.
 202   // If did_handle is false, then another commit will be retried soon.
 203   void BeginMainFrameAborted(bool did_handle);
 204
 205   // Set that we can create the first OutputSurface and start the scheduler.
 206   void SetCanStart() { can_start_ = true; }
 207
 208   void SetSkipNextBeginMainFrameToReduceLatency();
 209
 210   // Indicates whether drawing would, at this time, make sense.
 211   // CanDraw can be used to suppress flashes or checkerboarding
 212   // when such behavior would be undesirable.
 213   void SetCanDraw(bool can);
 214
 215   // Indicates that scheduled BeginMainFrame is started.
 216   void NotifyBeginMainFrameStarted();
 217
 218   // Indicates that the pending tree is ready for activation.
 219   void NotifyReadyToActivate();
 220
 221   bool has_pending_tree() const { return has_pending_tree_; }
 222   bool active_tree_needs_first_draw() const {
 223     return active_tree_needs_first_draw_;
 224   }
 225
 226   void DidManageTiles();
 227   void DidLoseOutputSurface();
 228   void DidCreateAndInitializeOutputSurface();
 229   bool HasInitializedOutputSurface() const;
 230
 231   // True if we need to abort draws to make forward progress.
 232   bool PendingDrawsShouldBeAborted() const;
 233
 234   bool SupportsProactiveBeginFrame() const;
 235
 236   void SetContinuousPainting(bool continuous_painting) {
 237     continuous_painting_ = continuous_painting;
 238   }
 239
 240   bool CouldSendBeginMainFrame() const;
 241
 242   // TODO(zmo): This is temporary for debugging crbug.com/393331.
 243   // We should remove it afterwards.
 244   std::string GetStatesForDebugging() const;
 245
 246  protected:
 247   bool BeginFrameNeededToAnimateOrDraw() const;
 248   bool ProactiveBeginFrameWanted() const;
 249
 250   // True if we need to force activations to make forward progress.
 251   bool PendingActivationsShouldBeForced() const;
 252
 253   bool ShouldAnimate() const;
 254   bool ShouldBeginOutputSurfaceCreation() const;
 255   bool ShouldDrawForced() const;
 256   bool ShouldDraw() const;
 257   bool ShouldActivatePendingTree() const;
 258   bool ShouldUpdateVisibleTiles() const;
 259   bool ShouldSendBeginMainFrame() const;
 260   bool ShouldCommit() const;
 261   bool ShouldManageTiles() const;
 262
 263   void AdvanceCurrentFrameNumber();
 264   bool HasSentBeginMainFrameThisFrame() const;
 265   bool HasUpdatedVisibleTilesThisFrame() const;
 266   bool HasRequestedSwapThisFrame() const;
 267   bool HasSwappedThisFrame() const;
 268
 269   void UpdateStateOnCommit(bool commit_was_aborted);
 270   void UpdateStateOnActivation();
 271   void UpdateStateOnDraw(bool did_request_swap);
 272   void UpdateStateOnManageTiles();
 273
 274   const SchedulerSettings settings_;
 275
 276   OutputSurfaceState output_surface_state_;
 277   BeginImplFrameState begin_impl_frame_state_;
 278   CommitState commit_state_;
 279   ForcedRedrawOnTimeoutState forced_redraw_state_;
 280
 281   BeginFrameArgs begin_impl_frame_args_;
 282
 283   int commit_count_;
 284   int current_frame_number_;
 285   int last_frame_number_animate_performed_;
 286   int last_frame_number_swap_performed_;
 287   int last_frame_number_swap_requested_;
 288   int last_frame_number_begin_main_frame_sent_;
 289   int last_frame_number_update_visible_tiles_was_called_;
 290
 291   // manage_tiles_funnel_ is "filled" each time ManageTiles is called
 292   // and "drained" on each BeginImplFrame. If the funnel gets too full,
 293   // we start throttling ACTION_MANAGE_TILES such that we average one
 294   // ManageTile per BeginImplFrame.
 295   int manage_tiles_funnel_;
 296   int consecutive_checkerboard_animations_;
 297   int max_pending_swaps_;
 298   int pending_swaps_;
 299   bool needs_redraw_;
 300   bool needs_animate_;
 301   bool needs_manage_tiles_;
 302   bool swap_used_incomplete_tile_;
 303   bool needs_commit_;
 304   bool inside_poll_for_anticipated_draw_triggers_;
 305   bool visible_;
 306   bool can_start_;
 307   bool can_draw_;
 308   bool has_pending_tree_;
 309   bool pending_tree_is_ready_for_activation_;
 310   bool active_tree_needs_first_draw_;
 311   bool did_create_and_initialize_first_output_surface_;
 312   bool impl_latency_takes_priority_;
 313   bool skip_next_begin_main_frame_to_reduce_latency_;
 314   bool skip_begin_main_frame_to_reduce_latency_;
 315   bool continuous_painting_;
 316
 317  private:
 318   DISALLOW_COPY_AND_ASSIGN(SchedulerStateMachine);
 319 };
 320
 321 }  // namespace cc
 322
 323 #endif  // CC_SCHEDULER_SCHEDULER_STATE_MACHINE_H_