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_swap_readback_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 TextureState {
  72     LAYER_TEXTURE_STATE_UNLOCKED,
  73     LAYER_TEXTURE_STATE_ACQUIRED_BY_MAIN_THREAD,
  74     LAYER_TEXTURE_STATE_ACQUIRED_BY_IMPL_THREAD,
  75   };
  76   static const char* TextureStateToString(TextureState state);
  77
  78   enum SynchronousReadbackState {
  79     READBACK_STATE_IDLE,
  80     READBACK_STATE_NEEDS_BEGIN_MAIN_FRAME,
  81     READBACK_STATE_WAITING_FOR_COMMIT,
  82     READBACK_STATE_WAITING_FOR_ACTIVATION,
  83     READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK,
  84     READBACK_STATE_WAITING_FOR_REPLACEMENT_COMMIT,
  85     READBACK_STATE_WAITING_FOR_REPLACEMENT_ACTIVATION,
  86   };
  87   static const char* SynchronousReadbackStateToString(
  88       SynchronousReadbackState state);
  89
  90   enum ForcedRedrawOnTimeoutState {
  91     FORCED_REDRAW_STATE_IDLE,
  92     FORCED_REDRAW_STATE_WAITING_FOR_COMMIT,
  93     FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION,
  94     FORCED_REDRAW_STATE_WAITING_FOR_DRAW,
  95   };
  96   static const char* ForcedRedrawOnTimeoutStateToString(
  97       ForcedRedrawOnTimeoutState state);
  98
  99   bool CommitPending() const {
 100     return commit_state_ == COMMIT_STATE_BEGIN_MAIN_FRAME_SENT ||
 101            commit_state_ == COMMIT_STATE_BEGIN_MAIN_FRAME_STARTED ||
 102            commit_state_ == COMMIT_STATE_READY_TO_COMMIT;
 103   }
 104   CommitState commit_state() const { return commit_state_; }
 105
 106   bool RedrawPending() const { return needs_redraw_; }
 107   bool ManageTilesPending() const { return needs_manage_tiles_; }
 108
 109   enum Action {
 110     ACTION_NONE,
 111     ACTION_SEND_BEGIN_MAIN_FRAME,
 112     ACTION_COMMIT,
 113     ACTION_UPDATE_VISIBLE_TILES,
 114     ACTION_ACTIVATE_PENDING_TREE,
 115     ACTION_DRAW_AND_SWAP_IF_POSSIBLE,
 116     ACTION_DRAW_AND_SWAP_FORCED,
 117     ACTION_DRAW_AND_SWAP_ABORT,
 118     ACTION_DRAW_AND_READBACK,
 119     ACTION_BEGIN_OUTPUT_SURFACE_CREATION,
 120     ACTION_ACQUIRE_LAYER_TEXTURES_FOR_MAIN_THREAD,
 121     ACTION_MANAGE_TILES,
 122   };
 123   static const char* ActionToString(Action action);
 124
 125   scoped_ptr<base::Value> AsValue() const;
 126
 127   Action NextAction() const;
 128   void UpdateState(Action action);
 129
 130   void CheckInvariants();
 131
 132   // Indicates whether the impl thread needs a BeginImplFrame callback in order
 133   // to make progress.
 134   bool BeginImplFrameNeeded() const;
 135
 136   // Indicates that we need to independently poll for new state and actions
 137   // because we can't expect a BeginImplFrame. This is mostly used to avoid
 138   // drawing repeat frames with the synchronous compositor without dropping
 139   // necessary actions on the floor.
 140   bool ShouldPollForAnticipatedDrawTriggers() const;
 141
 142   // Indicates that the system has entered and left a BeginImplFrame callback.
 143   // The scheduler will not draw more than once in a given BeginImplFrame
 144   // callback nor send more than one BeginMainFrame message.
 145   void OnBeginImplFrame(const BeginFrameArgs& args);
 146   void OnBeginImplFrameDeadlinePending();
 147   void OnBeginImplFrameDeadline();
 148   void OnBeginImplFrameIdle();
 149   bool ShouldTriggerBeginImplFrameDeadlineEarly() const;
 150   BeginImplFrameState begin_impl_frame_state() const {
 151     return begin_impl_frame_state_;
 152   }
 153
 154   // If the main thread didn't manage to produce a new frame in time for the
 155   // impl thread to draw, it is in a high latency mode.
 156   bool MainThreadIsInHighLatencyMode() const;
 157
 158   // PollForAnticipatedDrawTriggers is used by the synchronous compositor to
 159   // avoid requesting BeginImplFrames when we won't actually draw but still
 160   // need to advance our state at vsync intervals.
 161   void DidEnterPollForAnticipatedDrawTriggers();
 162   void DidLeavePollForAnticipatedDrawTriggers();
 163   bool inside_poll_for_anticipated_draw_triggers() const {
 164     return inside_poll_for_anticipated_draw_triggers_;
 165   }
 166
 167   // Indicates whether the LayerTreeHostImpl is visible.
 168   void SetVisible(bool visible);
 169
 170   // Indicates that a redraw is required, either due to the impl tree changing
 171   // or the screen being damaged and simply needing redisplay.
 172   void SetNeedsRedraw();
 173   bool needs_redraw() const { return needs_redraw_; }
 174
 175   // Indicates that manage-tiles is required. This guarantees another
 176   // ManageTiles will occur shortly (even if no redraw is required).
 177   void SetNeedsManageTiles();
 178
 179   // Indicates whether a redraw is required because we are currently rendering
 180   // with a low resolution or checkerboarded tile.
 181   void SetSwapUsedIncompleteTile(bool used_incomplete_tile);
 182
 183   // Indicates whether to prioritize animation smoothness over new content
 184   // activation.
 185   void SetSmoothnessTakesPriority(bool smoothness_takes_priority);
 186   bool smoothness_takes_priority() const { return smoothness_takes_priority_; }
 187
 188   // Indicates whether ACTION_DRAW_AND_SWAP_IF_POSSIBLE drew to the screen.
 189   void DidDrawIfPossibleCompleted(DrawSwapReadbackResult::DrawResult result);
 190
 191   // Indicates that a new commit flow needs to be performed, either to pull
 192   // updates from the main thread to the impl, or to push deltas from the impl
 193   // thread to main.
 194   void SetNeedsCommit();
 195
 196   // As SetNeedsCommit(), but ensures the BeginMainFrame will be sent even
 197   // if we are not visible.  After this call we expect to go through
 198   // the forced commit flow and then return to waiting for a non-forced
 199   // BeginMainFrame to finish.
 200   void SetNeedsForcedCommitForReadback();
 201
 202   // Call this only in response to receiving an ACTION_SEND_BEGIN_MAIN_FRAME
 203   // from NextAction.
 204   // Indicates that all painting is complete.
 205   void NotifyReadyToCommit();
 206
 207   // Call this only in response to receiving an ACTION_SEND_BEGIN_MAIN_FRAME
 208   // from NextAction if the client rejects the BeginMainFrame message.
 209   // If did_handle is false, then another commit will be retried soon.
 210   void BeginMainFrameAborted(bool did_handle);
 211
 212   // Request exclusive access to the textures that back single buffered
 213   // layers on behalf of the main thread. Upon acquisition,
 214   // ACTION_DRAW_AND_SWAP_IF_POSSIBLE will not draw until the main thread
 215   // releases the
 216   // textures to the impl thread by committing the layers.
 217   void SetMainThreadNeedsLayerTextures();
 218
 219   // Set that we can create the first OutputSurface and start the scheduler.
 220   void SetCanStart() { can_start_ = true; }
 221
 222   void SetSkipNextBeginMainFrameToReduceLatency();
 223
 224   // Indicates whether drawing would, at this time, make sense.
 225   // CanDraw can be used to suppress flashes or checkerboarding
 226   // when such behavior would be undesirable.
 227   void SetCanDraw(bool can);
 228
 229   // Indicates that scheduled BeginMainFrame is started.
 230   void NotifyBeginMainFrameStarted();
 231
 232   // Indicates that the pending tree is ready for activation.
 233   void NotifyReadyToActivate();
 234
 235   bool has_pending_tree() const { return has_pending_tree_; }
 236   bool active_tree_needs_first_draw() const {
 237     return active_tree_needs_first_draw_;
 238   }
 239
 240   void DidManageTiles();
 241   void DidLoseOutputSurface();
 242   void DidCreateAndInitializeOutputSurface();
 243   bool HasInitializedOutputSurface() const;
 244
 245   // True if we need to abort draws to make forward progress.
 246   bool PendingDrawsShouldBeAborted() const;
 247
 248   bool SupportsProactiveBeginImplFrame() const;
 249
 250  protected:
 251   bool BeginImplFrameNeededToDraw() const;
 252   bool ProactiveBeginImplFrameWanted() const;
 253
 254   // True if we need to force activations to make forward progress.
 255   bool PendingActivationsShouldBeForced() const;
 256
 257   bool ShouldBeginOutputSurfaceCreation() const;
 258   bool ShouldDrawForced() const;
 259   bool ShouldDraw() const;
 260   bool ShouldActivatePendingTree() const;
 261   bool ShouldAcquireLayerTexturesForMainThread() const;
 262   bool ShouldUpdateVisibleTiles() const;
 263   bool ShouldSendBeginMainFrame() const;
 264   bool ShouldCommit() const;
 265   bool ShouldManageTiles() const;
 266
 267   void AdvanceCurrentFrameNumber();
 268   bool HasSentBeginMainFrameThisFrame() const;
 269   bool HasScheduledManageTilesThisFrame() const;
 270   bool HasUpdatedVisibleTilesThisFrame() const;
 271   bool HasSwappedThisFrame() const;
 272
 273   void UpdateStateOnCommit(bool commit_was_aborted);
 274   void UpdateStateOnActivation();
 275   void UpdateStateOnDraw(bool did_swap);
 276   void UpdateStateOnManageTiles();
 277
 278   const SchedulerSettings settings_;
 279
 280   OutputSurfaceState output_surface_state_;
 281   BeginImplFrameState begin_impl_frame_state_;
 282   CommitState commit_state_;
 283   TextureState texture_state_;
 284   ForcedRedrawOnTimeoutState forced_redraw_state_;
 285   SynchronousReadbackState readback_state_;
 286
 287   BeginFrameArgs last_begin_impl_frame_args_;
 288
 289   int commit_count_;
 290   int current_frame_number_;
 291   int last_frame_number_swap_performed_;
 292   int last_frame_number_begin_main_frame_sent_;
 293   int last_frame_number_update_visible_tiles_was_called_;
 294
 295   // manage_tiles_funnel_ is "filled" each time ManageTiles is called
 296   // and "drained" on each BeginImplFrame. If the funnel gets too full,
 297   // we start throttling ACTION_MANAGE_TILES such that we average one
 298   // ManageTile per BeginImplFrame.
 299   int manage_tiles_funnel_;
 300   int consecutive_checkerboard_animations_;
 301   bool needs_redraw_;
 302   bool needs_manage_tiles_;
 303   bool swap_used_incomplete_tile_;
 304   bool needs_commit_;
 305   bool main_thread_needs_layer_textures_;
 306   bool inside_poll_for_anticipated_draw_triggers_;
 307   bool visible_;
 308   bool can_start_;
 309   bool can_draw_;
 310   bool has_pending_tree_;
 311   bool pending_tree_is_ready_for_activation_;
 312   bool active_tree_needs_first_draw_;
 313   bool draw_if_possible_failed_;
 314   bool did_create_and_initialize_first_output_surface_;
 315   bool smoothness_takes_priority_;
 316   bool skip_next_begin_main_frame_to_reduce_latency_;
 317   bool skip_begin_main_frame_to_reduce_latency_;
 318
 319  private:
 320   DISALLOW_COPY_AND_ASSIGN(SchedulerStateMachine);
 321 };
 322
 323 }  // namespace cc
 324
 325 #endif  // CC_SCHEDULER_SCHEDULER_STATE_MACHINE_H_