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_FRAME_IN_PROGRESS,
  64     COMMIT_STATE_READY_TO_COMMIT,
  65     COMMIT_STATE_WAITING_FOR_FIRST_DRAW,
  66   };
  67   static const char* CommitStateToString(CommitState state);
  68
  69   enum TextureState {
  70     LAYER_TEXTURE_STATE_UNLOCKED,
  71     LAYER_TEXTURE_STATE_ACQUIRED_BY_MAIN_THREAD,
  72     LAYER_TEXTURE_STATE_ACQUIRED_BY_IMPL_THREAD,
  73   };
  74   static const char* TextureStateToString(TextureState state);
  75
  76   enum SynchronousReadbackState {
  77     READBACK_STATE_IDLE,
  78     READBACK_STATE_NEEDS_BEGIN_MAIN_FRAME,
  79     READBACK_STATE_WAITING_FOR_COMMIT,
  80     READBACK_STATE_WAITING_FOR_ACTIVATION,
  81     READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK,
  82     READBACK_STATE_WAITING_FOR_REPLACEMENT_COMMIT,
  83     READBACK_STATE_WAITING_FOR_REPLACEMENT_ACTIVATION,
  84   };
  85   static const char* SynchronousReadbackStateToString(
  86       SynchronousReadbackState state);
  87
  88   enum ForcedRedrawOnTimeoutState {
  89     FORCED_REDRAW_STATE_IDLE,
  90     FORCED_REDRAW_STATE_WAITING_FOR_COMMIT,
  91     FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION,
  92     FORCED_REDRAW_STATE_WAITING_FOR_DRAW,
  93   };
  94   static const char* ForcedRedrawOnTimeoutStateToString(
  95       ForcedRedrawOnTimeoutState state);
  96
  97   bool CommitPending() const {
  98     return commit_state_ == COMMIT_STATE_FRAME_IN_PROGRESS ||
  99            commit_state_ == COMMIT_STATE_READY_TO_COMMIT;
 100   }
 101
 102   bool RedrawPending() const { return needs_redraw_; }
 103   bool ManageTilesPending() const { return needs_manage_tiles_; }
 104
 105   enum Action {
 106     ACTION_NONE,
 107     ACTION_SEND_BEGIN_MAIN_FRAME,
 108     ACTION_COMMIT,
 109     ACTION_UPDATE_VISIBLE_TILES,
 110     ACTION_ACTIVATE_PENDING_TREE,
 111     ACTION_DRAW_AND_SWAP_IF_POSSIBLE,
 112     ACTION_DRAW_AND_SWAP_FORCED,
 113     ACTION_DRAW_AND_SWAP_ABORT,
 114     ACTION_DRAW_AND_READBACK,
 115     ACTION_BEGIN_OUTPUT_SURFACE_CREATION,
 116     ACTION_ACQUIRE_LAYER_TEXTURES_FOR_MAIN_THREAD,
 117     ACTION_MANAGE_TILES,
 118   };
 119   static const char* ActionToString(Action action);
 120
 121   scoped_ptr<base::Value> AsValue() const;
 122
 123   Action NextAction() const;
 124   void UpdateState(Action action);
 125
 126   void CheckInvariants();
 127
 128   // Indicates whether the impl thread needs a BeginImplFrame callback in order
 129   // to make progress.
 130   bool BeginImplFrameNeeded() const;
 131
 132   // Indicates that we need to independently poll for new state and actions
 133   // because we can't expect a BeginImplFrame. This is mostly used to avoid
 134   // drawing repeat frames with the synchronous compositor without dropping
 135   // necessary actions on the floor.
 136   bool ShouldPollForAnticipatedDrawTriggers() const;
 137
 138   // Indicates that the system has entered and left a BeginImplFrame callback.
 139   // The scheduler will not draw more than once in a given BeginImplFrame
 140   // callback nor send more than one BeginMainFrame message.
 141   void OnBeginImplFrame(const BeginFrameArgs& args);
 142   void OnBeginImplFrameDeadlinePending();
 143   void OnBeginImplFrameDeadline();
 144   void OnBeginImplFrameIdle();
 145   bool ShouldTriggerBeginImplFrameDeadlineEarly() const;
 146   BeginImplFrameState begin_impl_frame_state() const {
 147     return begin_impl_frame_state_;
 148   }
 149
 150   // If the main thread didn't manage to produce a new frame in time for the
 151   // impl thread to draw, it is in a high latency mode.
 152   bool MainThreadIsInHighLatencyMode() const;
 153
 154   // PollForAnticipatedDrawTriggers is used by the synchronous compositor to
 155   // avoid requesting BeginImplFrames when we won't actually draw but still
 156   // need to advance our state at vsync intervals.
 157   void DidEnterPollForAnticipatedDrawTriggers();
 158   void DidLeavePollForAnticipatedDrawTriggers();
 159   bool inside_poll_for_anticipated_draw_triggers() const {
 160     return inside_poll_for_anticipated_draw_triggers_;
 161   }
 162
 163   // Indicates whether the LayerTreeHostImpl is visible.
 164   void SetVisible(bool visible);
 165
 166   // Indicates that a redraw is required, either due to the impl tree changing
 167   // or the screen being damaged and simply needing redisplay.
 168   void SetNeedsRedraw();
 169   bool needs_redraw() const { return needs_redraw_; }
 170
 171   // Indicates that manage-tiles is required. This guarantees another
 172   // ManageTiles will occur shortly (even if no redraw is required).
 173   void SetNeedsManageTiles();
 174
 175   // Indicates whether a redraw is required because we are currently rendering
 176   // with a low resolution or checkerboarded tile.
 177   void SetSwapUsedIncompleteTile(bool used_incomplete_tile);
 178
 179   // Indicates whether to prioritize animation smoothness over new content
 180   // activation.
 181   void SetSmoothnessTakesPriority(bool smoothness_takes_priority);
 182
 183   // Indicates whether ACTION_DRAW_AND_SWAP_IF_POSSIBLE drew to the screen.
 184   void DidDrawIfPossibleCompleted(DrawSwapReadbackResult::DrawResult result);
 185
 186   // Indicates that a new commit flow needs to be performed, either to pull
 187   // updates from the main thread to the impl, or to push deltas from the impl
 188   // thread to main.
 189   void SetNeedsCommit();
 190
 191   // As SetNeedsCommit(), but ensures the BeginMainFrame will be sent even
 192   // if we are not visible.  After this call we expect to go through
 193   // the forced commit flow and then return to waiting for a non-forced
 194   // BeginMainFrame to finish.
 195   void SetNeedsForcedCommitForReadback();
 196
 197   // Call this only in response to receiving an ACTION_SEND_BEGIN_MAIN_FRAME
 198   // from NextAction.
 199   // Indicates that all painting is complete.
 200   void FinishCommit();
 201
 202   // Call this only in response to receiving an ACTION_SEND_BEGIN_MAIN_FRAME
 203   // from NextAction if the client rejects the BeginMainFrame message.
 204   // If did_handle is false, then another commit will be retried soon.
 205   void BeginMainFrameAborted(bool did_handle);
 206
 207   // Request exclusive access to the textures that back single buffered
 208   // layers on behalf of the main thread. Upon acquisition,
 209   // ACTION_DRAW_AND_SWAP_IF_POSSIBLE will not draw until the main thread
 210   // releases the
 211   // textures to the impl thread by committing the layers.
 212   void SetMainThreadNeedsLayerTextures();
 213
 214   // Set that we can create the first OutputSurface and start the scheduler.
 215   void SetCanStart() { can_start_ = true; }
 216
 217   void SetSkipBeginMainFrameToReduceLatency(bool skip);
 218
 219   // Indicates whether drawing would, at this time, make sense.
 220   // CanDraw can be used to suppress flashes or checkerboarding
 221   // when such behavior would be undesirable.
 222   void SetCanDraw(bool can);
 223
 224   // Indicates that the pending tree is ready for activation.
 225   void NotifyReadyToActivate();
 226
 227   bool has_pending_tree() const { return has_pending_tree_; }
 228
 229   void DidManageTiles();
 230   void DidLoseOutputSurface();
 231   void DidCreateAndInitializeOutputSurface();
 232   bool HasInitializedOutputSurface() const;
 233
 234   // True if we need to abort draws to make forward progress.
 235   bool PendingDrawsShouldBeAborted() const;
 236
 237   bool SupportsProactiveBeginImplFrame() const;
 238
 239   bool IsCommitStateWaiting() const;
 240
 241  protected:
 242   bool BeginImplFrameNeededToDraw() const;
 243   bool ProactiveBeginImplFrameWanted() const;
 244
 245   // True if we need to force activations to make forward progress.
 246   bool PendingActivationsShouldBeForced() const;
 247
 248   bool ShouldBeginOutputSurfaceCreation() const;
 249   bool ShouldDrawForced() const;
 250   bool ShouldDraw() const;
 251   bool ShouldActivatePendingTree() const;
 252   bool ShouldAcquireLayerTexturesForMainThread() const;
 253   bool ShouldUpdateVisibleTiles() const;
 254   bool ShouldSendBeginMainFrame() const;
 255   bool ShouldCommit() const;
 256   bool ShouldManageTiles() const;
 257
 258   void AdvanceCurrentFrameNumber();
 259   bool HasSentBeginMainFrameThisFrame() const;
 260   bool HasScheduledManageTilesThisFrame() const;
 261   bool HasUpdatedVisibleTilesThisFrame() const;
 262   bool HasSwappedThisFrame() const;
 263
 264   void UpdateStateOnCommit(bool commit_was_aborted);
 265   void UpdateStateOnActivation();
 266   void UpdateStateOnDraw(bool did_swap);
 267   void UpdateStateOnManageTiles();
 268
 269   const SchedulerSettings settings_;
 270
 271   OutputSurfaceState output_surface_state_;
 272   BeginImplFrameState begin_impl_frame_state_;
 273   CommitState commit_state_;
 274   TextureState texture_state_;
 275   ForcedRedrawOnTimeoutState forced_redraw_state_;
 276   SynchronousReadbackState readback_state_;
 277
 278   BeginFrameArgs last_begin_impl_frame_args_;
 279
 280   int commit_count_;
 281   int current_frame_number_;
 282   int last_frame_number_swap_performed_;
 283   int last_frame_number_begin_main_frame_sent_;
 284   int last_frame_number_update_visible_tiles_was_called_;
 285
 286   // manage_tiles_funnel_ is "filled" each time ManageTiles is called
 287   // and "drained" on each BeginImplFrame. If the funnel gets too full,
 288   // we start throttling ACTION_MANAGE_TILES such that we average one
 289   // ManageTile per BeginImplFrame.
 290   int manage_tiles_funnel_;
 291   int consecutive_checkerboard_animations_;
 292   bool needs_redraw_;
 293   bool needs_manage_tiles_;
 294   bool swap_used_incomplete_tile_;
 295   bool needs_commit_;
 296   bool main_thread_needs_layer_textures_;
 297   bool inside_poll_for_anticipated_draw_triggers_;
 298   bool visible_;
 299   bool can_start_;
 300   bool can_draw_;
 301   bool has_pending_tree_;
 302   bool pending_tree_is_ready_for_activation_;
 303   bool active_tree_needs_first_draw_;
 304   bool draw_if_possible_failed_;
 305   bool did_create_and_initialize_first_output_surface_;
 306   bool smoothness_takes_priority_;
 307   bool skip_begin_main_frame_to_reduce_latency_;
 308
 309  private:
 310   DISALLOW_COPY_AND_ASSIGN(SchedulerStateMachine);
 311 };
 312
 313 }  // namespace cc
 314
 315 #endif  // CC_SCHEDULER_SCHEDULER_STATE_MACHINE_H_