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 class Value;
  20 }
  21
  22 namespace cc {
  23
  24 // The SchedulerStateMachine decides how to coordinate main thread activites
  25 // like painting/running javascript with rendering and input activities on the
  26 // impl thread.
  27 //
  28 // The state machine tracks internal state but is also influenced by external
  29 // state.  Internal state includes things like whether a frame has been
  30 // requested, while external state includes things like the current time being
  31 // near to the vblank time.
  32 //
  33 // The scheduler seperates "what to do next" from the updating of its internal
  34 // state to make testing cleaner.
  35 class CC_EXPORT SchedulerStateMachine {
  36  public:
  37   // settings must be valid for the lifetime of this class.
  38   explicit SchedulerStateMachine(const SchedulerSettings& settings);
  39
  40   enum OutputSurfaceState {
  41     OUTPUT_SURFACE_ACTIVE,
  42     OUTPUT_SURFACE_LOST,
  43     OUTPUT_SURFACE_CREATING,
  44     OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT,
  45     OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION,
  46   };
  47   static const char* OutputSurfaceStateToString(OutputSurfaceState state);
  48
  49   // Note: BeginImplFrameState will always cycle through all the states in
  50   // order. Whether or not it actually waits or draws, it will at least try to
  51   // wait in BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME and try to draw in
  52   // BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE
  53   enum BeginImplFrameState {
  54     BEGIN_IMPL_FRAME_STATE_IDLE,
  55     BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING,
  56     BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME,
  57     BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE,
  58   };
  59   static const char* BeginImplFrameStateToString(BeginImplFrameState state);
  60
  61   enum CommitState {
  62     COMMIT_STATE_IDLE,
  63     COMMIT_STATE_BEGIN_MAIN_FRAME_SENT,
  64     COMMIT_STATE_BEGIN_MAIN_FRAME_STARTED,
  65     COMMIT_STATE_READY_TO_COMMIT,
  66     COMMIT_STATE_WAITING_FOR_ACTIVATION,
  67     COMMIT_STATE_WAITING_FOR_FIRST_DRAW,
  68   };
  69   static const char* CommitStateToString(CommitState state);
  70
  71   enum ForcedRedrawOnTimeoutState {
  72     FORCED_REDRAW_STATE_IDLE,
  73     FORCED_REDRAW_STATE_WAITING_FOR_COMMIT,
  74     FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION,
  75     FORCED_REDRAW_STATE_WAITING_FOR_DRAW,
  76   };
  77   static const char* ForcedRedrawOnTimeoutStateToString(
  78       ForcedRedrawOnTimeoutState state);
  79
  80   bool CommitPending() const {
  81     return commit_state_ == COMMIT_STATE_BEGIN_MAIN_FRAME_SENT ||
  82            commit_state_ == COMMIT_STATE_BEGIN_MAIN_FRAME_STARTED ||
  83            commit_state_ == COMMIT_STATE_READY_TO_COMMIT;
  84   }
  85   CommitState commit_state() const { return commit_state_; }
  86
  87   bool RedrawPending() const { return needs_redraw_; }
  88   bool ManageTilesPending() const { return needs_manage_tiles_; }
  89
  90   enum Action {
  91     ACTION_NONE,
  92     ACTION_ANIMATE,
  93     ACTION_SEND_BEGIN_MAIN_FRAME,
  94     ACTION_COMMIT,
  95     ACTION_UPDATE_VISIBLE_TILES,
  96     ACTION_ACTIVATE_PENDING_TREE,
  97     ACTION_DRAW_AND_SWAP_IF_POSSIBLE,
  98     ACTION_DRAW_AND_SWAP_FORCED,
  99     ACTION_DRAW_AND_SWAP_ABORT,
 100     ACTION_BEGIN_OUTPUT_SURFACE_CREATION,
 101     ACTION_MANAGE_TILES,
 102   };
 103   static const char* ActionToString(Action action);
 104
 105   scoped_ptr<base::Value> AsValue() const;
 106
 107   Action NextAction() const;
 108   void UpdateState(Action action);
 109
 110   // Indicates whether the impl thread needs a BeginImplFrame callback in order
 111   // to make progress.
 112   bool BeginFrameNeeded() const;
 113
 114   // Indicates that we need to independently poll for new state and actions
 115   // because we can't expect a BeginImplFrame. This is mostly used to avoid
 116   // drawing repeat frames with the synchronous compositor without dropping
 117   // necessary actions on the floor.
 118   bool ShouldPollForAnticipatedDrawTriggers() const;
 119
 120   // Indicates that the system has entered and left a BeginImplFrame callback.
 121   // The scheduler will not draw more than once in a given BeginImplFrame
 122   // callback nor send more than one BeginMainFrame message.
 123   void OnBeginImplFrame(const BeginFrameArgs& args);
 124   void OnBeginImplFrameDeadlinePending();
 125   void OnBeginImplFrameDeadline();
 126   void OnBeginImplFrameIdle();
 127   bool ShouldTriggerBeginImplFrameDeadlineEarly() const;
 128   BeginImplFrameState begin_impl_frame_state() const {
 129     return begin_impl_frame_state_;
 130   }
 131
 132   // If the main thread didn't manage to produce a new frame in time for the
 133   // impl thread to draw, it is in a high latency mode.
 134   bool MainThreadIsInHighLatencyMode() const;
 135
 136   // PollForAnticipatedDrawTriggers is used by the synchronous compositor to
 137   // avoid requesting BeginImplFrames when we won't actually draw but still
 138   // need to advance our state at vsync intervals.
 139   void DidEnterPollForAnticipatedDrawTriggers();
 140   void DidLeavePollForAnticipatedDrawTriggers();
 141   bool inside_poll_for_anticipated_draw_triggers() const {
 142     return inside_poll_for_anticipated_draw_triggers_;
 143   }
 144
 145   // Indicates whether the LayerTreeHostImpl is visible.
 146   void SetVisible(bool visible);
 147
 148   // Indicates that a redraw is required, either due to the impl tree changing
 149   // or the screen being damaged and simply needing redisplay.
 150   void SetNeedsRedraw();
 151   bool needs_redraw() const { return needs_redraw_; }
 152
 153   void SetNeedsAnimate();
 154   bool needs_animate() const { return needs_animate_; }
 155
 156   // Indicates that manage-tiles is required. This guarantees another
 157   // ManageTiles will occur shortly (even if no redraw is required).
 158   void SetNeedsManageTiles();
 159
 160   // Sets how many swaps can be pending to the OutputSurface.
 161   void SetMaxSwapsPending(int max);
 162
 163   // If the scheduler attempted to draw and swap, this provides feedback
 164   // regarding whether or not the swap actually occured. We might skip the
 165   // swap when there is not damage, for example.
 166   void DidSwapBuffers();
 167
 168   // Indicates whether a redraw is required because we are currently rendering
 169   // with a low resolution or checkerboarded tile.
 170   void SetSwapUsedIncompleteTile(bool used_incomplete_tile);
 171
 172   // Notification from the OutputSurface that a swap has been consumed.
 173   void DidSwapBuffersComplete();
 174
 175   // Indicates whether to prioritize animation smoothness over new content
 176   // activation.
 177   void SetSmoothnessTakesPriority(bool smoothness_takes_priority);
 178   bool smoothness_takes_priority() const { return smoothness_takes_priority_; }
 179
 180   // Indicates whether ACTION_DRAW_AND_SWAP_IF_POSSIBLE drew to the screen.
 181   void DidDrawIfPossibleCompleted(DrawResult result);
 182
 183   // Indicates that a new commit flow needs to be performed, either to pull
 184   // updates from the main thread to the impl, or to push deltas from the impl
 185   // thread to main.
 186   void SetNeedsCommit();
 187
 188   // Call this only in response to receiving an ACTION_SEND_BEGIN_MAIN_FRAME
 189   // from NextAction.
 190   // Indicates that all painting is complete.
 191   void NotifyReadyToCommit();
 192
 193   // Call this only in response to receiving an ACTION_SEND_BEGIN_MAIN_FRAME
 194   // from NextAction if the client rejects the BeginMainFrame message.
 195   // If did_handle is false, then another commit will be retried soon.
 196   void BeginMainFrameAborted(bool did_handle);
 197
 198   // Set that we can create the first OutputSurface and start the scheduler.
 199   void SetCanStart() { can_start_ = true; }
 200
 201   void SetSkipNextBeginMainFrameToReduceLatency();
 202
 203   // Indicates whether drawing would, at this time, make sense.
 204   // CanDraw can be used to suppress flashes or checkerboarding
 205   // when such behavior would be undesirable.
 206   void SetCanDraw(bool can);
 207
 208   // Indicates that scheduled BeginMainFrame is started.
 209   void NotifyBeginMainFrameStarted();
 210
 211   // Indicates that the pending tree is ready for activation.
 212   void NotifyReadyToActivate();
 213
 214   bool has_pending_tree() const { return has_pending_tree_; }
 215   bool active_tree_needs_first_draw() const {
 216     return active_tree_needs_first_draw_;
 217   }
 218
 219   void DidManageTiles();
 220   void DidLoseOutputSurface();
 221   void DidCreateAndInitializeOutputSurface();
 222   bool HasInitializedOutputSurface() const;
 223
 224   // True if we need to abort draws to make forward progress.
 225   bool PendingDrawsShouldBeAborted() const;
 226
 227   bool SupportsProactiveBeginFrame() const;
 228
 229   void SetContinuousPainting(bool continuous_painting) {
 230     continuous_painting_ = continuous_painting;
 231   }
 232
 233  protected:
 234   bool BeginFrameNeededToAnimateOrDraw() const;
 235   bool ProactiveBeginFrameWanted() const;
 236
 237   // True if we need to force activations to make forward progress.
 238   bool PendingActivationsShouldBeForced() const;
 239
 240   bool ShouldAnimate() const;
 241   bool ShouldBeginOutputSurfaceCreation() const;
 242   bool ShouldDrawForced() const;
 243   bool ShouldDraw() const;
 244   bool ShouldActivatePendingTree() const;
 245   bool ShouldUpdateVisibleTiles() const;
 246   bool ShouldSendBeginMainFrame() const;
 247   bool ShouldCommit() const;
 248   bool ShouldManageTiles() const;
 249
 250   void AdvanceCurrentFrameNumber();
 251   bool HasSentBeginMainFrameThisFrame() const;
 252   bool HasUpdatedVisibleTilesThisFrame() const;
 253   bool HasRequestedSwapThisFrame() const;
 254   bool HasSwappedThisFrame() const;
 255
 256   void UpdateStateOnCommit(bool commit_was_aborted);
 257   void UpdateStateOnActivation();
 258   void UpdateStateOnDraw(bool did_request_swap);
 259   void UpdateStateOnManageTiles();
 260
 261   const SchedulerSettings settings_;
 262
 263   OutputSurfaceState output_surface_state_;
 264   BeginImplFrameState begin_impl_frame_state_;
 265   CommitState commit_state_;
 266   ForcedRedrawOnTimeoutState forced_redraw_state_;
 267
 268   BeginFrameArgs begin_impl_frame_args_;
 269
 270   int commit_count_;
 271   int current_frame_number_;
 272   int last_frame_number_animate_performed_;
 273   int last_frame_number_swap_performed_;
 274   int last_frame_number_swap_requested_;
 275   int last_frame_number_begin_main_frame_sent_;
 276   int last_frame_number_update_visible_tiles_was_called_;
 277
 278   // manage_tiles_funnel_ is "filled" each time ManageTiles is called
 279   // and "drained" on each BeginImplFrame. If the funnel gets too full,
 280   // we start throttling ACTION_MANAGE_TILES such that we average one
 281   // ManageTile per BeginImplFrame.
 282   int manage_tiles_funnel_;
 283   int consecutive_checkerboard_animations_;
 284   int max_pending_swaps_;
 285   int pending_swaps_;
 286   bool needs_redraw_;
 287   bool needs_animate_;
 288   bool needs_manage_tiles_;
 289   bool swap_used_incomplete_tile_;
 290   bool needs_commit_;
 291   bool inside_poll_for_anticipated_draw_triggers_;
 292   bool visible_;
 293   bool can_start_;
 294   bool can_draw_;
 295   bool has_pending_tree_;
 296   bool pending_tree_is_ready_for_activation_;
 297   bool active_tree_needs_first_draw_;
 298   bool did_create_and_initialize_first_output_surface_;
 299   bool smoothness_takes_priority_;
 300   bool skip_next_begin_main_frame_to_reduce_latency_;
 301   bool skip_begin_main_frame_to_reduce_latency_;
 302   bool continuous_painting_;
 303
 304  private:
 305   DISALLOW_COPY_AND_ASSIGN(SchedulerStateMachine);
 306 };
 307
 308 }  // namespace cc
 309
 310 #endif  // CC_SCHEDULER_SCHEDULER_STATE_MACHINE_H_