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 SynchronousReadbackState {
  72     READBACK_STATE_IDLE,
  73     READBACK_STATE_NEEDS_BEGIN_MAIN_FRAME,
  74     READBACK_STATE_WAITING_FOR_COMMIT,
  75     READBACK_STATE_WAITING_FOR_ACTIVATION,
  76     READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK,
  77     READBACK_STATE_WAITING_FOR_REPLACEMENT_COMMIT,
  78     READBACK_STATE_WAITING_FOR_REPLACEMENT_ACTIVATION,
  79   };
  80   static const char* SynchronousReadbackStateToString(
  81       SynchronousReadbackState state);
  82
  83   enum ForcedRedrawOnTimeoutState {
  84     FORCED_REDRAW_STATE_IDLE,
  85     FORCED_REDRAW_STATE_WAITING_FOR_COMMIT,
  86     FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION,
  87     FORCED_REDRAW_STATE_WAITING_FOR_DRAW,
  88   };
  89   static const char* ForcedRedrawOnTimeoutStateToString(
  90       ForcedRedrawOnTimeoutState state);
  91
  92   bool CommitPending() const {
  93     return commit_state_ == COMMIT_STATE_BEGIN_MAIN_FRAME_SENT ||
  94            commit_state_ == COMMIT_STATE_BEGIN_MAIN_FRAME_STARTED ||
  95            commit_state_ == COMMIT_STATE_READY_TO_COMMIT;
  96   }
  97   CommitState commit_state() const { return commit_state_; }
  98
  99   bool RedrawPending() const { return needs_redraw_; }
 100   bool ManageTilesPending() const { return needs_manage_tiles_; }
 101
 102   enum Action {
 103     ACTION_NONE,
 104     ACTION_ANIMATE,
 105     ACTION_SEND_BEGIN_MAIN_FRAME,
 106     ACTION_COMMIT,
 107     ACTION_UPDATE_VISIBLE_TILES,
 108     ACTION_ACTIVATE_PENDING_TREE,
 109     ACTION_DRAW_AND_SWAP_IF_POSSIBLE,
 110     ACTION_DRAW_AND_SWAP_FORCED,
 111     ACTION_DRAW_AND_SWAP_ABORT,
 112     ACTION_DRAW_AND_READBACK,
 113     ACTION_BEGIN_OUTPUT_SURFACE_CREATION,
 114     ACTION_MANAGE_TILES,
 115   };
 116   static const char* ActionToString(Action action);
 117
 118   scoped_ptr<base::Value> AsValue() const;
 119
 120   Action NextAction() const;
 121   void UpdateState(Action action);
 122
 123   void CheckInvariants();
 124
 125   // Indicates whether the impl thread needs a BeginImplFrame callback in order
 126   // to make progress.
 127   bool BeginFrameNeeded() const;
 128
 129   // Indicates that we need to independently poll for new state and actions
 130   // because we can't expect a BeginImplFrame. This is mostly used to avoid
 131   // drawing repeat frames with the synchronous compositor without dropping
 132   // necessary actions on the floor.
 133   bool ShouldPollForAnticipatedDrawTriggers() const;
 134
 135   // Indicates that the system has entered and left a BeginImplFrame callback.
 136   // The scheduler will not draw more than once in a given BeginImplFrame
 137   // callback nor send more than one BeginMainFrame message.
 138   void OnBeginImplFrame(const BeginFrameArgs& args);
 139   void OnBeginImplFrameDeadlinePending();
 140   void OnBeginImplFrameDeadline();
 141   void OnBeginImplFrameIdle();
 142   bool ShouldTriggerBeginImplFrameDeadlineEarly() const;
 143   BeginImplFrameState begin_impl_frame_state() const {
 144     return begin_impl_frame_state_;
 145   }
 146
 147   // If the main thread didn't manage to produce a new frame in time for the
 148   // impl thread to draw, it is in a high latency mode.
 149   bool MainThreadIsInHighLatencyMode() const;
 150
 151   // PollForAnticipatedDrawTriggers is used by the synchronous compositor to
 152   // avoid requesting BeginImplFrames when we won't actually draw but still
 153   // need to advance our state at vsync intervals.
 154   void DidEnterPollForAnticipatedDrawTriggers();
 155   void DidLeavePollForAnticipatedDrawTriggers();
 156   bool inside_poll_for_anticipated_draw_triggers() const {
 157     return inside_poll_for_anticipated_draw_triggers_;
 158   }
 159
 160   // Indicates whether the LayerTreeHostImpl is visible.
 161   void SetVisible(bool visible);
 162
 163   // Indicates that a redraw is required, either due to the impl tree changing
 164   // or the screen being damaged and simply needing redisplay.
 165   void SetNeedsRedraw();
 166   bool needs_redraw() const { return needs_redraw_; }
 167
 168   void SetNeedsAnimate();
 169   bool needs_animate() const { return needs_animate_; }
 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   // Sets how many swaps can be pending to the OutputSurface.
 176   void SetMaxSwapsPending(int max);
 177
 178   // If the scheduler attempted to draw and swap, this provides feedback
 179   // regarding whether or not the swap actually occured. We might skip the
 180   // swap when there is not damage, for example.
 181   void DidSwapBuffers();
 182
 183   // Indicates whether a redraw is required because we are currently rendering
 184   // with a low resolution or checkerboarded tile.
 185   void SetSwapUsedIncompleteTile(bool used_incomplete_tile);
 186
 187   // Notification from the OutputSurface that a swap has been consumed.
 188   void DidSwapBuffersComplete();
 189
 190   // Indicates whether to prioritize animation smoothness over new content
 191   // activation.
 192   void SetSmoothnessTakesPriority(bool smoothness_takes_priority);
 193   bool smoothness_takes_priority() const { return smoothness_takes_priority_; }
 194
 195   // Indicates whether ACTION_DRAW_AND_SWAP_IF_POSSIBLE drew to the screen.
 196   void DidDrawIfPossibleCompleted(DrawSwapReadbackResult::DrawResult result);
 197
 198   // Indicates that a new commit flow needs to be performed, either to pull
 199   // updates from the main thread to the impl, or to push deltas from the impl
 200   // thread to main.
 201   void SetNeedsCommit();
 202
 203   // As SetNeedsCommit(), but ensures the BeginMainFrame will be sent even
 204   // if we are not visible.  After this call we expect to go through
 205   // the forced commit flow and then return to waiting for a non-forced
 206   // BeginMainFrame to finish.
 207   void SetNeedsForcedCommitForReadback();
 208
 209   // Call this only in response to receiving an ACTION_SEND_BEGIN_MAIN_FRAME
 210   // from NextAction.
 211   // Indicates that all painting is complete.
 212   void NotifyReadyToCommit();
 213
 214   // Call this only in response to receiving an ACTION_SEND_BEGIN_MAIN_FRAME
 215   // from NextAction if the client rejects the BeginMainFrame message.
 216   // If did_handle is false, then another commit will be retried soon.
 217   void BeginMainFrameAborted(bool did_handle);
 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 SupportsProactiveBeginFrame() const;
 249
 250   void SetContinuousPainting(bool continuous_painting) {
 251     continuous_painting_ = continuous_painting;
 252   }
 253
 254  protected:
 255   bool BeginFrameNeededToAnimateOrDraw() const;
 256   bool ProactiveBeginFrameWanted() const;
 257
 258   // True if we need to force activations to make forward progress.
 259   bool PendingActivationsShouldBeForced() const;
 260
 261   bool ShouldAnimate() const;
 262   bool ShouldBeginOutputSurfaceCreation() const;
 263   bool ShouldDrawForced() const;
 264   bool ShouldDraw() const;
 265   bool ShouldActivatePendingTree() const;
 266   bool ShouldUpdateVisibleTiles() const;
 267   bool ShouldSendBeginMainFrame() const;
 268   bool ShouldCommit() const;
 269   bool ShouldManageTiles() const;
 270
 271   void AdvanceCurrentFrameNumber();
 272   bool HasSentBeginMainFrameThisFrame() const;
 273   bool HasUpdatedVisibleTilesThisFrame() const;
 274   bool HasSwappedThisFrame() const;
 275
 276   void UpdateStateOnCommit(bool commit_was_aborted);
 277   void UpdateStateOnActivation();
 278   void UpdateStateOnDraw(bool did_request_swap);
 279   void UpdateStateOnManageTiles();
 280
 281   const SchedulerSettings settings_;
 282
 283   OutputSurfaceState output_surface_state_;
 284   BeginImplFrameState begin_impl_frame_state_;
 285   CommitState commit_state_;
 286   ForcedRedrawOnTimeoutState forced_redraw_state_;
 287   SynchronousReadbackState readback_state_;
 288
 289   BeginFrameArgs begin_impl_frame_args_;
 290
 291   int commit_count_;
 292   int current_frame_number_;
 293   int last_frame_number_animate_performed_;
 294   int last_frame_number_swap_performed_;
 295   int last_frame_number_begin_main_frame_sent_;
 296   int last_frame_number_update_visible_tiles_was_called_;
 297
 298   // manage_tiles_funnel_ is "filled" each time ManageTiles is called
 299   // and "drained" on each BeginImplFrame. If the funnel gets too full,
 300   // we start throttling ACTION_MANAGE_TILES such that we average one
 301   // ManageTile per BeginImplFrame.
 302   int manage_tiles_funnel_;
 303   int consecutive_checkerboard_animations_;
 304   int max_pending_swaps_;
 305   int pending_swaps_;
 306   bool needs_redraw_;
 307   bool needs_animate_;
 308   bool needs_manage_tiles_;
 309   bool swap_used_incomplete_tile_;
 310   bool needs_commit_;
 311   bool inside_poll_for_anticipated_draw_triggers_;
 312   bool visible_;
 313   bool can_start_;
 314   bool can_draw_;
 315   bool has_pending_tree_;
 316   bool pending_tree_is_ready_for_activation_;
 317   bool active_tree_needs_first_draw_;
 318   bool did_create_and_initialize_first_output_surface_;
 319   bool smoothness_takes_priority_;
 320   bool skip_next_begin_main_frame_to_reduce_latency_;
 321   bool skip_begin_main_frame_to_reduce_latency_;
 322   bool continuous_painting_;
 323   bool needs_back_to_back_readback_;
 324
 325  private:
 326   DISALLOW_COPY_AND_ASSIGN(SchedulerStateMachine);
 327 };
 328
 329 }  // namespace cc
 330
 331 #endif  // CC_SCHEDULER_SCHEDULER_STATE_MACHINE_H_