cc/scheduler/scheduler_state_machine.cc

   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 #include "cc/scheduler/scheduler_state_machine.h"
   6
   7 #include "base/format_macros.h"
   8 #include "base/logging.h"
   9 #include "base/strings/stringprintf.h"
  10 #include "base/trace_event/trace_event.h"
  11 #include "base/trace_event/trace_event_argument.h"
  12 #include "base/values.h"
  13 #include "ui/gfx/frame_time.h"
  14
  15 namespace cc {
  16
  17 SchedulerStateMachine::SchedulerStateMachine(const SchedulerSettings& settings)
  18     : settings_(settings),
  19       output_surface_state_(OUTPUT_SURFACE_LOST),
  20       begin_impl_frame_state_(BEGIN_IMPL_FRAME_STATE_IDLE),
  21       commit_state_(COMMIT_STATE_IDLE),
  22       forced_redraw_state_(FORCED_REDRAW_STATE_IDLE),
  23       commit_count_(0),
  24       current_frame_number_(0),
  25       last_frame_number_animate_performed_(-1),
  26       last_frame_number_swap_performed_(-1),
  27       last_frame_number_swap_requested_(-1),
  28       last_frame_number_begin_main_frame_sent_(-1),
  29       last_frame_number_invalidate_output_surface_performed_(-1),
  30       animate_funnel_(false),
  31       request_swap_funnel_(false),
  32       send_begin_main_frame_funnel_(false),
  33       invalidate_output_surface_funnel_(false),
  34       prepare_tiles_funnel_(0),
  35       consecutive_checkerboard_animations_(0),
  36       max_pending_swaps_(1),
  37       pending_swaps_(0),
  38       needs_redraw_(false),
  39       needs_animate_(false),
  40       needs_prepare_tiles_(false),
  41       needs_commit_(false),
  42       visible_(false),
  43       can_start_(false),
  44       can_draw_(false),
  45       has_pending_tree_(false),
  46       pending_tree_is_ready_for_activation_(false),
  47       active_tree_needs_first_draw_(false),
  48       did_create_and_initialize_first_output_surface_(false),
  49       impl_latency_takes_priority_(false),
  50       skip_next_begin_main_frame_to_reduce_latency_(false),
  51       skip_begin_main_frame_to_reduce_latency_(false),
  52       continuous_painting_(false),
  53       children_need_begin_frames_(false),
  54       defer_commits_(false),
  55       video_needs_begin_frames_(false),
  56       last_commit_had_no_updates_(false),
  57       wait_for_active_tree_ready_to_draw_(false),
  58       did_request_swap_in_last_frame_(false),
  59       did_perform_swap_in_last_draw_(false) {
  60 }
  61
  62 const char* SchedulerStateMachine::OutputSurfaceStateToString(
  63     OutputSurfaceState state) {
  64   switch (state) {
  65     case OUTPUT_SURFACE_ACTIVE:
  66       return "OUTPUT_SURFACE_ACTIVE";
  67     case OUTPUT_SURFACE_LOST:
  68       return "OUTPUT_SURFACE_LOST";
  69     case OUTPUT_SURFACE_CREATING:
  70       return "OUTPUT_SURFACE_CREATING";
  71     case OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT:
  72       return "OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT";
  73     case OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION:
  74       return "OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION";
  75   }
  76   NOTREACHED();
  77   return "???";
  78 }
  79
  80 const char* SchedulerStateMachine::BeginImplFrameStateToString(
  81     BeginImplFrameState state) {
  82   switch (state) {
  83     case BEGIN_IMPL_FRAME_STATE_IDLE:
  84       return "BEGIN_IMPL_FRAME_STATE_IDLE";
  85     case BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING:
  86       return "BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING";
  87     case BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME:
  88       return "BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME";
  89     case BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE:
  90       return "BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE";
  91   }
  92   NOTREACHED();
  93   return "???";
  94 }
  95
  96 const char* SchedulerStateMachine::BeginImplFrameDeadlineModeToString(
  97     BeginImplFrameDeadlineMode mode) {
  98   switch (mode) {
  99     case BEGIN_IMPL_FRAME_DEADLINE_MODE_NONE:
 100       return "BEGIN_IMPL_FRAME_DEADLINE_MODE_NONE";
 101     case BEGIN_IMPL_FRAME_DEADLINE_MODE_IMMEDIATE:
 102       return "BEGIN_IMPL_FRAME_DEADLINE_MODE_IMMEDIATE";
 103     case BEGIN_IMPL_FRAME_DEADLINE_MODE_REGULAR:
 104       return "BEGIN_IMPL_FRAME_DEADLINE_MODE_REGULAR";
 105     case BEGIN_IMPL_FRAME_DEADLINE_MODE_LATE:
 106       return "BEGIN_IMPL_FRAME_DEADLINE_MODE_LATE";
 107     case BEGIN_IMPL_FRAME_DEADLINE_MODE_BLOCKED_ON_READY_TO_DRAW:
 108       return "BEGIN_IMPL_FRAME_DEADLINE_MODE_BLOCKED_ON_READY_TO_DRAW";
 109   }
 110   NOTREACHED();
 111   return "???";
 112 }
 113
 114 const char* SchedulerStateMachine::CommitStateToString(CommitState state) {
 115   switch (state) {
 116     case COMMIT_STATE_IDLE:
 117       return "COMMIT_STATE_IDLE";
 118     case COMMIT_STATE_BEGIN_MAIN_FRAME_SENT:
 119       return "COMMIT_STATE_BEGIN_MAIN_FRAME_SENT";
 120     case COMMIT_STATE_BEGIN_MAIN_FRAME_STARTED:
 121       return "COMMIT_STATE_BEGIN_MAIN_FRAME_STARTED";
 122     case COMMIT_STATE_READY_TO_COMMIT:
 123       return "COMMIT_STATE_READY_TO_COMMIT";
 124     case COMMIT_STATE_WAITING_FOR_ACTIVATION:
 125       return "COMMIT_STATE_WAITING_FOR_ACTIVATION";
 126     case COMMIT_STATE_WAITING_FOR_DRAW:
 127       return "COMMIT_STATE_WAITING_FOR_DRAW";
 128   }
 129   NOTREACHED();
 130   return "???";
 131 }
 132
 133 const char* SchedulerStateMachine::ForcedRedrawOnTimeoutStateToString(
 134     ForcedRedrawOnTimeoutState state) {
 135   switch (state) {
 136     case FORCED_REDRAW_STATE_IDLE:
 137       return "FORCED_REDRAW_STATE_IDLE";
 138     case FORCED_REDRAW_STATE_WAITING_FOR_COMMIT:
 139       return "FORCED_REDRAW_STATE_WAITING_FOR_COMMIT";
 140     case FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION:
 141       return "FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION";
 142     case FORCED_REDRAW_STATE_WAITING_FOR_DRAW:
 143       return "FORCED_REDRAW_STATE_WAITING_FOR_DRAW";
 144   }
 145   NOTREACHED();
 146   return "???";
 147 }
 148
 149 const char* SchedulerStateMachine::ActionToString(Action action) {
 150   switch (action) {
 151     case ACTION_NONE:
 152       return "ACTION_NONE";
 153     case ACTION_ANIMATE:
 154       return "ACTION_ANIMATE";
 155     case ACTION_SEND_BEGIN_MAIN_FRAME:
 156       return "ACTION_SEND_BEGIN_MAIN_FRAME";
 157     case ACTION_COMMIT:
 158       return "ACTION_COMMIT";
 159     case ACTION_ACTIVATE_SYNC_TREE:
 160       return "ACTION_ACTIVATE_SYNC_TREE";
 161     case ACTION_DRAW_AND_SWAP_IF_POSSIBLE:
 162       return "ACTION_DRAW_AND_SWAP_IF_POSSIBLE";
 163     case ACTION_DRAW_AND_SWAP_FORCED:
 164       return "ACTION_DRAW_AND_SWAP_FORCED";
 165     case ACTION_DRAW_AND_SWAP_ABORT:
 166       return "ACTION_DRAW_AND_SWAP_ABORT";
 167     case ACTION_BEGIN_OUTPUT_SURFACE_CREATION:
 168       return "ACTION_BEGIN_OUTPUT_SURFACE_CREATION";
 169     case ACTION_PREPARE_TILES:
 170       return "ACTION_PREPARE_TILES";
 171     case ACTION_INVALIDATE_OUTPUT_SURFACE:
 172       return "ACTION_INVALIDATE_OUTPUT_SURFACE";
 173   }
 174   NOTREACHED();
 175   return "???";
 176 }
 177
 178 scoped_refptr<base::trace_event::ConvertableToTraceFormat>
 179 SchedulerStateMachine::AsValue() const {
 180   scoped_refptr<base::trace_event::TracedValue> state =
 181       new base::trace_event::TracedValue();
 182   AsValueInto(state.get());
 183   return state;
 184 }
 185
 186 void SchedulerStateMachine::AsValueInto(
 187     base::trace_event::TracedValue* state) const {
 188   state->BeginDictionary("major_state");
 189   state->SetString("next_action", ActionToString(NextAction()));
 190   state->SetString("begin_impl_frame_state",
 191                    BeginImplFrameStateToString(begin_impl_frame_state_));
 192   state->SetString("commit_state", CommitStateToString(commit_state_));
 193   state->SetString("output_surface_state_",
 194                    OutputSurfaceStateToString(output_surface_state_));
 195   state->SetString("forced_redraw_state",
 196                    ForcedRedrawOnTimeoutStateToString(forced_redraw_state_));
 197   state->EndDictionary();
 198
 199   state->BeginDictionary("minor_state");
 200   state->SetInteger("commit_count", commit_count_);
 201   state->SetInteger("current_frame_number", current_frame_number_);
 202   state->SetInteger("last_frame_number_animate_performed",
 203                     last_frame_number_animate_performed_);
 204   state->SetInteger("last_frame_number_swap_performed",
 205                     last_frame_number_swap_performed_);
 206   state->SetInteger("last_frame_number_swap_requested",
 207                     last_frame_number_swap_requested_);
 208   state->SetInteger("last_frame_number_begin_main_frame_sent",
 209                     last_frame_number_begin_main_frame_sent_);
 210   state->SetBoolean("funnel: animate_funnel", animate_funnel_);
 211   state->SetBoolean("funnel: request_swap_funnel", request_swap_funnel_);
 212   state->SetBoolean("funnel: send_begin_main_frame_funnel",
 213                     send_begin_main_frame_funnel_);
 214   state->SetInteger("funnel: prepare_tiles_funnel", prepare_tiles_funnel_);
 215   state->SetBoolean("funnel: invalidate_output_surface_funnel",
 216                     invalidate_output_surface_funnel_);
 217   state->SetInteger("consecutive_checkerboard_animations",
 218                     consecutive_checkerboard_animations_);
 219   state->SetInteger("max_pending_swaps_", max_pending_swaps_);
 220   state->SetInteger("pending_swaps_", pending_swaps_);
 221   state->SetBoolean("needs_redraw", needs_redraw_);
 222   state->SetBoolean("needs_animate_", needs_animate_);
 223   state->SetBoolean("needs_prepare_tiles", needs_prepare_tiles_);
 224   state->SetBoolean("needs_commit", needs_commit_);
 225   state->SetBoolean("visible", visible_);
 226   state->SetBoolean("can_start", can_start_);
 227   state->SetBoolean("can_draw", can_draw_);
 228   state->SetBoolean("has_pending_tree", has_pending_tree_);
 229   state->SetBoolean("pending_tree_is_ready_for_activation",
 230                     pending_tree_is_ready_for_activation_);
 231   state->SetBoolean("active_tree_needs_first_draw",
 232                     active_tree_needs_first_draw_);
 233   state->SetBoolean("wait_for_active_tree_ready_to_draw",
 234                     wait_for_active_tree_ready_to_draw_);
 235   state->SetBoolean("did_create_and_initialize_first_output_surface",
 236                     did_create_and_initialize_first_output_surface_);
 237   state->SetBoolean("impl_latency_takes_priority",
 238                     impl_latency_takes_priority_);
 239   state->SetBoolean("main_thread_is_in_high_latency_mode",
 240                     MainThreadIsInHighLatencyMode());
 241   state->SetBoolean("skip_begin_main_frame_to_reduce_latency",
 242                     skip_begin_main_frame_to_reduce_latency_);
 243   state->SetBoolean("skip_next_begin_main_frame_to_reduce_latency",
 244                     skip_next_begin_main_frame_to_reduce_latency_);
 245   state->SetBoolean("continuous_painting", continuous_painting_);
 246   state->SetBoolean("children_need_begin_frames", children_need_begin_frames_);
 247   state->SetBoolean("video_needs_begin_frames", video_needs_begin_frames_);
 248   state->SetBoolean("defer_commits", defer_commits_);
 249   state->SetBoolean("last_commit_had_no_updates", last_commit_had_no_updates_);
 250   state->SetBoolean("did_request_swap_in_last_frame",
 251                     did_request_swap_in_last_frame_);
 252   state->SetBoolean("did_perform_swap_in_last_draw",
 253                     did_perform_swap_in_last_draw_);
 254   state->EndDictionary();
 255 }
 256
 257 bool SchedulerStateMachine::PendingDrawsShouldBeAborted() const {
 258   // These are all the cases where we normally cannot or do not want to draw
 259   // but, if needs_redraw_ is true and we do not draw to make forward progress,
 260   // we might deadlock with the main thread.
 261   // This should be a superset of PendingActivationsShouldBeForced() since
 262   // activation of the pending tree is blocked by drawing of the active tree and
 263   // the main thread might be blocked on activation of the most recent commit.
 264   if (PendingActivationsShouldBeForced())
 265     return true;
 266
 267   // Additional states where we should abort draws.
 268   if (!can_draw_)
 269     return true;
 270   return false;
 271 }
 272
 273 bool SchedulerStateMachine::PendingActivationsShouldBeForced() const {
 274   // There is no output surface to trigger our activations.
 275   // If we do not force activations to make forward progress, we might deadlock
 276   // with the main thread.
 277   if (output_surface_state_ == OUTPUT_SURFACE_LOST)
 278     return true;
 279
 280   // If we're not visible, we should force activation.
 281   // Since we set RequiresHighResToDraw when becoming visible, we ensure that we
 282   // don't checkerboard until all visible resources are done. Furthermore, if we
 283   // do keep the pending tree around, when becoming visible we might activate
 284   // prematurely causing RequiresHighResToDraw flag to be reset. In all cases,
 285   // we can simply activate on becoming invisible since we don't need to draw
 286   // the active tree when we're in this state.
 287   if (!visible_)
 288     return true;
 289
 290   return false;
 291 }
 292
 293 bool SchedulerStateMachine::ShouldBeginOutputSurfaceCreation() const {
 294   // Don't try to initialize too early.
 295   if (!can_start_)
 296     return false;
 297
 298   // We only want to start output surface initialization after the
 299   // previous commit is complete.
 300   if (commit_state_ != COMMIT_STATE_IDLE)
 301     return false;
 302
 303   // Make sure the BeginImplFrame from any previous OutputSurfaces
 304   // are complete before creating the new OutputSurface.
 305   if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_IDLE)
 306     return false;
 307
 308   // We want to clear the pipeline of any pending draws and activations
 309   // before starting output surface initialization. This allows us to avoid
 310   // weird corner cases where we abort draws or force activation while we
 311   // are initializing the output surface.
 312   if (active_tree_needs_first_draw_ || has_pending_tree_)
 313     return false;
 314
 315   // We need to create the output surface if we don't have one and we haven't
 316   // started creating one yet.
 317   return output_surface_state_ == OUTPUT_SURFACE_LOST;
 318 }
 319
 320 bool SchedulerStateMachine::ShouldDraw() const {
 321   // If we need to abort draws, we should do so ASAP since the draw could
 322   // be blocking other important actions (like output surface initialization),
 323   // from occurring. If we are waiting for the first draw, then perform the
 324   // aborted draw to keep things moving. If we are not waiting for the first
 325   // draw however, we don't want to abort for no reason.
 326   if (PendingDrawsShouldBeAborted())
 327     return active_tree_needs_first_draw_;
 328
 329   // Do not draw too many times in a single frame. It's okay that we don't check
 330   // this before checking for aborted draws because aborted draws do not request
 331   // a swap.
 332   if (request_swap_funnel_)
 333     return false;
 334
 335   // Don't draw if we are waiting on the first commit after a surface.
 336   if (output_surface_state_ != OUTPUT_SURFACE_ACTIVE)
 337     return false;
 338
 339   // Do not queue too many swaps.
 340   if (pending_swaps_ >= max_pending_swaps_)
 341     return false;
 342
 343   // Except for the cases above, do not draw outside of the BeginImplFrame
 344   // deadline.
 345   if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE)
 346     return false;
 347
 348   // Only handle forced redraws due to timeouts on the regular deadline.
 349   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
 350     return true;
 351
 352   return needs_redraw_;
 353 }
 354
 355 bool SchedulerStateMachine::ShouldActivatePendingTree() const {
 356   // There is nothing to activate.
 357   if (!has_pending_tree_)
 358     return false;
 359
 360   // We should not activate a second tree before drawing the first one.
 361   // Even if we need to force activation of the pending tree, we should abort
 362   // drawing the active tree first.
 363   if (active_tree_needs_first_draw_)
 364     return false;
 365
 366   // If we want to force activation, do so ASAP.
 367   if (PendingActivationsShouldBeForced())
 368     return true;
 369
 370   // At this point, only activate if we are ready to activate.
 371   return pending_tree_is_ready_for_activation_;
 372 }
 373
 374 bool SchedulerStateMachine::ShouldAnimate() const {
 375   // Do not animate too many times in a single frame.
 376   if (animate_funnel_)
 377     return false;
 378
 379   // Don't animate if we are waiting on the first commit after a surface.
 380   if (output_surface_state_ != OUTPUT_SURFACE_ACTIVE)
 381     return false;
 382
 383   if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING &&
 384       begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE)
 385     return false;
 386
 387   return needs_redraw_ || needs_animate_;
 388 }
 389
 390 bool SchedulerStateMachine::CouldSendBeginMainFrame() const {
 391   if (!needs_commit_)
 392     return false;
 393
 394   // We can not perform commits if we are not visible.
 395   if (!visible_)
 396     return false;
 397
 398   // Do not make a new commits when it is deferred.
 399   if (defer_commits_)
 400     return false;
 401
 402   return true;
 403 }
 404
 405 bool SchedulerStateMachine::SendingBeginMainFrameMightCauseDeadlock() const {
 406   // NPAPI is the only case where the UI thread makes synchronous calls to the
 407   // Renderer main thread. During that synchronous call, we may not get a
 408   // SwapAck for the UI thread, which may prevent BeginMainFrame's from
 409   // completing if there's enough back pressure. If the BeginMainFrame can't
 410   // make progress, the Renderer can't service the UI thread's synchronous call
 411   // and we have deadlock.
 412   // This returns true if there's too much backpressure to finish a commit
 413   // if we were to initiate a BeginMainFrame.
 414   return has_pending_tree_ && active_tree_needs_first_draw_ &&
 415          pending_swaps_ >= max_pending_swaps_;
 416 }
 417
 418 bool SchedulerStateMachine::ShouldSendBeginMainFrame() const {
 419   if (!CouldSendBeginMainFrame())
 420     return false;
 421
 422   // Do not send begin main frame too many times in a single frame.
 423   if (send_begin_main_frame_funnel_)
 424     return false;
 425
 426   // Only send BeginMainFrame when there isn't another commit pending already.
 427   // Other parts of the state machine indirectly defer the BeginMainFrame
 428   // by transitioning to WAITING commit states rather than going
 429   // immediately to IDLE.
 430   if (commit_state_ != COMMIT_STATE_IDLE)
 431     return false;
 432
 433   // Don't send BeginMainFrame early if we are prioritizing the active tree
 434   // because of impl_latency_takes_priority_.
 435   if (impl_latency_takes_priority_ &&
 436       (has_pending_tree_ || active_tree_needs_first_draw_)) {
 437     return false;
 438   }
 439
 440   // We should not send BeginMainFrame while we are in
 441   // BEGIN_IMPL_FRAME_STATE_IDLE since we might have new
 442   // user input arriving soon.
 443   // TODO(brianderson): Allow sending BeginMainFrame while idle when the main
 444   // thread isn't consuming user input.
 445   if (begin_impl_frame_state_ == BEGIN_IMPL_FRAME_STATE_IDLE &&
 446       BeginFrameNeeded())
 447     return false;
 448
 449   // We need a new commit for the forced redraw. This honors the
 450   // single commit per interval because the result will be swapped to screen.
 451   // TODO(brianderson): Remove this or move it below the
 452   // SendingBeginMainFrameMightCauseDeadlock check since  we want to avoid
 453   // ever returning true from this method if we might cause deadlock.
 454   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_COMMIT)
 455     return true;
 456
 457   // We shouldn't normally accept commits if there isn't an OutputSurface.
 458   if (!HasInitializedOutputSurface())
 459     return false;
 460
 461   // Make sure the BeginMainFrame can finish eventually if we start it.
 462   if (SendingBeginMainFrameMightCauseDeadlock())
 463     return false;
 464
 465   if (!settings_.main_frame_while_swap_throttled_enabled) {
 466     // SwapAck throttle the BeginMainFrames unless we just swapped to
 467     // potentially improve impl-thread latency over main-thread throughput.
 468     // TODO(brianderson): Remove this restriction to improve throughput or
 469     // make it conditional on impl_latency_takes_priority_.
 470     bool just_swapped_in_deadline =
 471         begin_impl_frame_state_ == BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE &&
 472         did_perform_swap_in_last_draw_;
 473     if (pending_swaps_ >= max_pending_swaps_ && !just_swapped_in_deadline)
 474       return false;
 475   }
 476
 477   if (skip_begin_main_frame_to_reduce_latency_)
 478     return false;
 479
 480   return true;
 481 }
 482
 483 bool SchedulerStateMachine::ShouldCommit() const {
 484   if (commit_state_ != COMMIT_STATE_READY_TO_COMMIT)
 485     return false;
 486
 487   // We must not finish the commit until the pending tree is free.
 488   if (has_pending_tree_) {
 489     DCHECK(settings_.main_frame_before_activation_enabled);
 490     return false;
 491   }
 492
 493   // If impl-side-painting, commit to the pending tree as soon as we can.
 494   if (settings_.impl_side_painting)
 495     return true;
 496
 497   // If we only have an active tree, it is incorrect to replace it
 498   // before we've drawn it when we aren't impl-side-painting.
 499   DCHECK(!settings_.impl_side_painting);
 500   return !active_tree_needs_first_draw_;
 501 }
 502
 503 bool SchedulerStateMachine::ShouldPrepareTiles() const {
 504   // PrepareTiles only really needs to be called immediately after commit
 505   // and then periodically after that. Use a funnel to make sure we average
 506   // one PrepareTiles per BeginImplFrame in the long run.
 507   if (prepare_tiles_funnel_ > 0)
 508     return false;
 509
 510   // Limiting to once per-frame is not enough, since we only want to
 511   // prepare tiles _after_ draws.
 512   if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE)
 513     return false;
 514
 515   return needs_prepare_tiles_;
 516 }
 517
 518 bool SchedulerStateMachine::ShouldInvalidateOutputSurface() const {
 519   // Do not invalidate too many times in a frame.
 520   if (invalidate_output_surface_funnel_)
 521     return false;
 522
 523   // Only the synchronous compositor requires invalidations.
 524   if (!settings_.using_synchronous_renderer_compositor)
 525     return false;
 526
 527   // Invalidations are only performed inside a BeginFrame.
 528   if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING)
 529     return false;
 530
 531   // TODO(sunnyps): needs_prepare_tiles_ is needed here because PrepareTiles is
 532   // called only inside the deadline / draw phase. We could remove this if we
 533   // allowed PrepareTiles to happen in OnBeginImplFrame.
 534   return needs_redraw_ || needs_prepare_tiles_;
 535 }
 536
 537 SchedulerStateMachine::Action SchedulerStateMachine::NextAction() const {
 538   if (ShouldActivatePendingTree())
 539     return ACTION_ACTIVATE_SYNC_TREE;
 540   if (ShouldCommit())
 541     return ACTION_COMMIT;
 542   if (ShouldAnimate())
 543     return ACTION_ANIMATE;
 544   if (ShouldDraw()) {
 545     if (PendingDrawsShouldBeAborted())
 546       return ACTION_DRAW_AND_SWAP_ABORT;
 547     else if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
 548       return ACTION_DRAW_AND_SWAP_FORCED;
 549     else
 550       return ACTION_DRAW_AND_SWAP_IF_POSSIBLE;
 551   }
 552   if (ShouldPrepareTiles())
 553     return ACTION_PREPARE_TILES;
 554   if (ShouldSendBeginMainFrame())
 555     return ACTION_SEND_BEGIN_MAIN_FRAME;
 556   if (ShouldInvalidateOutputSurface())
 557     return ACTION_INVALIDATE_OUTPUT_SURFACE;
 558   if (ShouldBeginOutputSurfaceCreation())
 559     return ACTION_BEGIN_OUTPUT_SURFACE_CREATION;
 560   return ACTION_NONE;
 561 }
 562
 563 void SchedulerStateMachine::UpdateState(Action action) {
 564   switch (action) {
 565     case ACTION_NONE:
 566       return;
 567
 568     case ACTION_ACTIVATE_SYNC_TREE:
 569       UpdateStateOnActivation();
 570       return;
 571
 572     case ACTION_ANIMATE:
 573       UpdateStateOnAnimate();
 574       return;
 575
 576     case ACTION_SEND_BEGIN_MAIN_FRAME:
 577       UpdateStateOnSendBeginMainFrame();
 578       return;
 579
 580     case ACTION_COMMIT: {
 581       bool commit_has_no_updates = false;
 582       UpdateStateOnCommit(commit_has_no_updates);
 583       return;
 584     }
 585
 586     case ACTION_DRAW_AND_SWAP_FORCED:
 587     case ACTION_DRAW_AND_SWAP_IF_POSSIBLE: {
 588       bool did_request_swap = true;
 589       UpdateStateOnDraw(did_request_swap);
 590       return;
 591     }
 592
 593     case ACTION_DRAW_AND_SWAP_ABORT: {
 594       bool did_request_swap = false;
 595       UpdateStateOnDraw(did_request_swap);
 596       return;
 597     }
 598
 599     case ACTION_BEGIN_OUTPUT_SURFACE_CREATION:
 600       UpdateStateOnBeginOutputSurfaceCreation();
 601       return;
 602
 603     case ACTION_PREPARE_TILES:
 604       UpdateStateOnPrepareTiles();
 605       return;
 606
 607     case ACTION_INVALIDATE_OUTPUT_SURFACE:
 608       UpdateStateOnInvalidateOutputSurface();
 609       return;
 610   }
 611 }
 612
 613 void SchedulerStateMachine::UpdateStateOnAnimate() {
 614   DCHECK(!animate_funnel_);
 615   last_frame_number_animate_performed_ = current_frame_number_;
 616   animate_funnel_ = true;
 617   needs_animate_ = false;
 618   // TODO(skyostil): Instead of assuming this, require the client to tell us.
 619   SetNeedsRedraw();
 620 }
 621
 622 void SchedulerStateMachine::UpdateStateOnSendBeginMainFrame() {
 623   DCHECK(!has_pending_tree_ || settings_.main_frame_before_activation_enabled);
 624   DCHECK(visible_);
 625   DCHECK(!send_begin_main_frame_funnel_);
 626   commit_state_ = COMMIT_STATE_BEGIN_MAIN_FRAME_SENT;
 627   needs_commit_ = false;
 628   send_begin_main_frame_funnel_ = true;
 629   last_frame_number_begin_main_frame_sent_ = current_frame_number_;
 630 }
 631
 632 void SchedulerStateMachine::UpdateStateOnCommit(bool commit_has_no_updates) {
 633   commit_count_++;
 634
 635   // Animate after commit even if we've already animated.
 636   if (!commit_has_no_updates)
 637     animate_funnel_ = false;
 638
 639   if (commit_has_no_updates || settings_.main_frame_before_activation_enabled) {
 640     commit_state_ = COMMIT_STATE_IDLE;
 641   } else if (settings_.impl_side_painting) {
 642     commit_state_ = COMMIT_STATE_WAITING_FOR_ACTIVATION;
 643   } else {
 644     commit_state_ = settings_.main_thread_should_always_be_low_latency
 645                         ? COMMIT_STATE_WAITING_FOR_DRAW
 646                         : COMMIT_STATE_IDLE;
 647   }
 648
 649   // If we are impl-side-painting but the commit was aborted, then we behave
 650   // mostly as if we are not impl-side-painting since there is no pending tree.
 651   has_pending_tree_ = settings_.impl_side_painting && !commit_has_no_updates;
 652
 653   // Update state related to forced draws.
 654   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_COMMIT) {
 655     forced_redraw_state_ = has_pending_tree_
 656                                ? FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION
 657                                : FORCED_REDRAW_STATE_WAITING_FOR_DRAW;
 658   }
 659
 660   // Update the output surface state.
 661   DCHECK_NE(output_surface_state_, OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION);
 662   if (output_surface_state_ == OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT) {
 663     if (has_pending_tree_) {
 664       output_surface_state_ = OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION;
 665     } else {
 666       output_surface_state_ = OUTPUT_SURFACE_ACTIVE;
 667       needs_redraw_ = true;
 668     }
 669   }
 670
 671   // Update state if we have a new active tree to draw, or if the active tree
 672   // was unchanged but we need to do a forced draw.
 673   if (!has_pending_tree_ &&
 674       (!commit_has_no_updates ||
 675        forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)) {
 676     needs_redraw_ = true;
 677     active_tree_needs_first_draw_ = true;
 678   }
 679
 680   // This post-commit work is common to both completed and aborted commits.
 681   pending_tree_is_ready_for_activation_ = false;
 682
 683   if (continuous_painting_)
 684     needs_commit_ = true;
 685   last_commit_had_no_updates_ = commit_has_no_updates;
 686 }
 687
 688 void SchedulerStateMachine::UpdateStateOnActivation() {
 689   if (commit_state_ == COMMIT_STATE_WAITING_FOR_ACTIVATION) {
 690     commit_state_ = settings_.main_thread_should_always_be_low_latency
 691                         ? COMMIT_STATE_WAITING_FOR_DRAW
 692                         : COMMIT_STATE_IDLE;
 693   }
 694
 695   if (output_surface_state_ == OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION)
 696     output_surface_state_ = OUTPUT_SURFACE_ACTIVE;
 697
 698   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION)
 699     forced_redraw_state_ = FORCED_REDRAW_STATE_WAITING_FOR_DRAW;
 700
 701   has_pending_tree_ = false;
 702   pending_tree_is_ready_for_activation_ = false;
 703   active_tree_needs_first_draw_ = true;
 704   needs_redraw_ = true;
 705 }
 706
 707 void SchedulerStateMachine::UpdateStateOnDraw(bool did_request_swap) {
 708   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
 709     forced_redraw_state_ = FORCED_REDRAW_STATE_IDLE;
 710
 711   if (commit_state_ == COMMIT_STATE_WAITING_FOR_DRAW)
 712     commit_state_ = COMMIT_STATE_IDLE;
 713
 714   needs_redraw_ = false;
 715   active_tree_needs_first_draw_ = false;
 716
 717   if (did_request_swap) {
 718     DCHECK(!request_swap_funnel_);
 719     request_swap_funnel_ = true;
 720     did_request_swap_in_last_frame_ = true;
 721     last_frame_number_swap_requested_ = current_frame_number_;
 722   }
 723 }
 724
 725 void SchedulerStateMachine::UpdateStateOnPrepareTiles() {
 726   needs_prepare_tiles_ = false;
 727 }
 728
 729 void SchedulerStateMachine::UpdateStateOnBeginOutputSurfaceCreation() {
 730   DCHECK_EQ(output_surface_state_, OUTPUT_SURFACE_LOST);
 731   output_surface_state_ = OUTPUT_SURFACE_CREATING;
 732
 733   // The following DCHECKs make sure we are in the proper quiescent state.
 734   // The pipeline should be flushed entirely before we start output
 735   // surface creation to avoid complicated corner cases.
 736   DCHECK_EQ(commit_state_, COMMIT_STATE_IDLE);
 737   DCHECK(!has_pending_tree_);
 738   DCHECK(!active_tree_needs_first_draw_);
 739 }
 740
 741 void SchedulerStateMachine::UpdateStateOnInvalidateOutputSurface() {
 742   DCHECK(!invalidate_output_surface_funnel_);
 743   invalidate_output_surface_funnel_ = true;
 744   last_frame_number_invalidate_output_surface_performed_ =
 745       current_frame_number_;
 746
 747   // The synchronous compositor makes no guarantees about a draw coming in after
 748   // an invalidate so clear any flags that would cause the compositor's pipeline
 749   // to stall.
 750   active_tree_needs_first_draw_ = false;  // blocks commit if true
 751 }
 752
 753 void SchedulerStateMachine::SetSkipNextBeginMainFrameToReduceLatency() {
 754   TRACE_EVENT_INSTANT0("cc",
 755                        "Scheduler: SkipNextBeginMainFrameToReduceLatency",
 756                        TRACE_EVENT_SCOPE_THREAD);
 757   skip_next_begin_main_frame_to_reduce_latency_ = true;
 758 }
 759
 760 bool SchedulerStateMachine::BeginFrameRequiredForChildren() const {
 761   return children_need_begin_frames_;
 762 }
 763 bool SchedulerStateMachine::BeginFrameNeededForVideo() const {
 764   return video_needs_begin_frames_;
 765 }
 766
 767 bool SchedulerStateMachine::BeginFrameNeeded() const {
 768   // We can't handle BeginFrames when output surface isn't initialized.
 769   // TODO(brianderson): Support output surface creation inside a BeginFrame.
 770   if (!HasInitializedOutputSurface())
 771     return false;
 772
 773   // If we are not visible, we don't need BeginFrame messages.
 774   if (!visible_)
 775     return false;
 776
 777   return (BeginFrameRequiredForAction() || BeginFrameRequiredForChildren() ||
 778           BeginFrameNeededForVideo() || ProactiveBeginFrameWanted());
 779 }
 780
 781 void SchedulerStateMachine::SetChildrenNeedBeginFrames(
 782     bool children_need_begin_frames) {
 783   children_need_begin_frames_ = children_need_begin_frames;
 784 }
 785
 786 void SchedulerStateMachine::SetVideoNeedsBeginFrames(
 787     bool video_needs_begin_frames) {
 788   video_needs_begin_frames_ = video_needs_begin_frames;
 789 }
 790
 791 void SchedulerStateMachine::SetDeferCommits(bool defer_commits) {
 792   defer_commits_ = defer_commits;
 793 }
 794
 795 // These are the cases where we require a BeginFrame message to make progress
 796 // on requested actions.
 797 bool SchedulerStateMachine::BeginFrameRequiredForAction() const {
 798   // The forced draw respects our normal draw scheduling, so we need to
 799   // request a BeginImplFrame for it.
 800   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
 801     return true;
 802
 803   return needs_animate_ || needs_redraw_ || (needs_commit_ && !defer_commits_);
 804 }
 805
 806 // These are cases where we are very likely want a BeginFrame message in the
 807 // near future. Proactively requesting the BeginImplFrame helps hide the round
 808 // trip latency of the SetNeedsBeginFrame request that has to go to the
 809 // Browser.
 810 // This includes things like drawing soon, but might not actually have a new
 811 // frame to draw when we receive the next BeginImplFrame.
 812 bool SchedulerStateMachine::ProactiveBeginFrameWanted() const {
 813   // Do not be proactive when invisible.
 814   if (!visible_)
 815     return false;
 816
 817   // We should proactively request a BeginImplFrame if a commit is pending
 818   // because we will want to draw if the commit completes quickly. Do not
 819   // request frames when commits are disabled, because the frame requests will
 820   // not provide the needed commit (and will wake up the process when it could
 821   // stay idle).
 822   if ((commit_state_ != COMMIT_STATE_IDLE) && !defer_commits_)
 823     return true;
 824
 825   // If the pending tree activates quickly, we'll want a BeginImplFrame soon
 826   // to draw the new active tree.
 827   if (has_pending_tree_)
 828     return true;
 829
 830   // Changing priorities may allow us to activate (given the new priorities),
 831   // which may result in a new frame.
 832   if (needs_prepare_tiles_)
 833     return true;
 834
 835   // If we just sent a swap request, it's likely that we are going to produce
 836   // another frame soon. This helps avoid negative glitches in our
 837   // SetNeedsBeginFrame requests, which may propagate to the BeginImplFrame
 838   // provider and get sampled at an inopportune time, delaying the next
 839   // BeginImplFrame.
 840   if (did_request_swap_in_last_frame_)
 841     return true;
 842
 843   // If the last commit was aborted because of early out (no updates), we should
 844   // still want a begin frame in case there is a commit coming again.
 845   if (last_commit_had_no_updates_)
 846     return true;
 847
 848   return false;
 849 }
 850
 851 void SchedulerStateMachine::OnBeginImplFrame() {
 852   begin_impl_frame_state_ = BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING;
 853   current_frame_number_++;
 854
 855   last_commit_had_no_updates_ = false;
 856   did_request_swap_in_last_frame_ = false;
 857
 858   // Clear funnels for any actions we perform during the frame.
 859   animate_funnel_ = false;
 860   send_begin_main_frame_funnel_ = false;
 861   invalidate_output_surface_funnel_ = false;
 862
 863   // "Drain" the PrepareTiles funnel.
 864   if (prepare_tiles_funnel_ > 0)
 865     prepare_tiles_funnel_--;
 866
 867   skip_begin_main_frame_to_reduce_latency_ =
 868       skip_next_begin_main_frame_to_reduce_latency_;
 869   skip_next_begin_main_frame_to_reduce_latency_ = false;
 870 }
 871
 872 void SchedulerStateMachine::OnBeginImplFrameDeadlinePending() {
 873   begin_impl_frame_state_ = BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME;
 874 }
 875
 876 void SchedulerStateMachine::OnBeginImplFrameDeadline() {
 877   begin_impl_frame_state_ = BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE;
 878
 879   did_perform_swap_in_last_draw_ = false;
 880
 881   // Clear funnels for any actions we perform during the deadline.
 882   request_swap_funnel_ = false;
 883 }
 884
 885 void SchedulerStateMachine::OnBeginImplFrameIdle() {
 886   begin_impl_frame_state_ = BEGIN_IMPL_FRAME_STATE_IDLE;
 887 }
 888
 889 SchedulerStateMachine::BeginImplFrameDeadlineMode
 890 SchedulerStateMachine::CurrentBeginImplFrameDeadlineMode() const {
 891   if (settings_.using_synchronous_renderer_compositor) {
 892     // No deadline for synchronous compositor.
 893     return BEGIN_IMPL_FRAME_DEADLINE_MODE_NONE;
 894   } else if (wait_for_active_tree_ready_to_draw_) {
 895     // When we are waiting for ready to draw signal, we do not wait to post a
 896     // deadline yet.
 897     return BEGIN_IMPL_FRAME_DEADLINE_MODE_BLOCKED_ON_READY_TO_DRAW;
 898   } else if (ShouldTriggerBeginImplFrameDeadlineImmediately()) {
 899     return BEGIN_IMPL_FRAME_DEADLINE_MODE_IMMEDIATE;
 900   } else if (needs_redraw_ && pending_swaps_ < max_pending_swaps_) {
 901     // We have an animation or fast input path on the impl thread that wants
 902     // to draw, so don't wait too long for a new active tree.
 903     // If we are swap throttled we should wait until we are unblocked.
 904     return BEGIN_IMPL_FRAME_DEADLINE_MODE_REGULAR;
 905   } else {
 906     // The impl thread doesn't have anything it wants to draw and we are just
 907     // waiting for a new active tree or we are swap throttled. In short we are
 908     // blocked.
 909     return BEGIN_IMPL_FRAME_DEADLINE_MODE_LATE;
 910   }
 911 }
 912
 913 bool SchedulerStateMachine::ShouldTriggerBeginImplFrameDeadlineImmediately()
 914     const {
 915   // TODO(brianderson): This should take into account multiple commit sources.
 916   if (begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME)
 917     return false;
 918
 919   // If we just forced activation, we should end the deadline right now.
 920   if (PendingActivationsShouldBeForced() && !has_pending_tree_)
 921     return true;
 922
 923   // SwapAck throttle the deadline since we wont draw and swap anyway.
 924   if (pending_swaps_ >= max_pending_swaps_)
 925     return false;
 926
 927   if (active_tree_needs_first_draw_)
 928     return true;
 929
 930   if (!needs_redraw_)
 931     return false;
 932
 933   // This is used to prioritize impl-thread draws when the main thread isn't
 934   // producing anything, e.g., after an aborted commit. We also check that we
 935   // don't have a pending tree -- otherwise we should give it a chance to
 936   // activate.
 937   // TODO(skyostil): Revisit this when we have more accurate deadline estimates.
 938   if (commit_state_ == COMMIT_STATE_IDLE && !has_pending_tree_)
 939     return true;
 940
 941   // Prioritize impl-thread draws in impl_latency_takes_priority_ mode.
 942   if (impl_latency_takes_priority_)
 943     return true;
 944
 945   return false;
 946 }
 947
 948 bool SchedulerStateMachine::MainThreadIsInHighLatencyMode() const {
 949   // If a commit is pending before the previous commit has been drawn, we
 950   // are definitely in a high latency mode.
 951   if (CommitPending() && (active_tree_needs_first_draw_ || has_pending_tree_))
 952     return true;
 953
 954   // If we just sent a BeginMainFrame and haven't hit the deadline yet, the main
 955   // thread is in a low latency mode.
 956   if (send_begin_main_frame_funnel_ &&
 957       (begin_impl_frame_state_ == BEGIN_IMPL_FRAME_STATE_BEGIN_FRAME_STARTING ||
 958        begin_impl_frame_state_ == BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME))
 959     return false;
 960
 961   // If there's a commit in progress it must either be from the previous frame
 962   // or it started after the impl thread's deadline. In either case the main
 963   // thread is in high latency mode.
 964   if (CommitPending())
 965     return true;
 966
 967   // Similarly, if there's a pending tree the main thread is in high latency
 968   // mode, because either
 969   //   it's from the previous frame
 970   // or
 971   //   we're currently drawing the active tree and the pending tree will thus
 972   //   only be drawn in the next frame.
 973   if (has_pending_tree_)
 974     return true;
 975
 976   if (begin_impl_frame_state_ == BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE) {
 977     // Even if there's a new active tree to draw at the deadline or we've just
 978     // swapped it, it may have been triggered by a previous BeginImplFrame, in
 979     // which case the main thread is in a high latency mode.
 980     return (active_tree_needs_first_draw_ || did_perform_swap_in_last_draw_) &&
 981            !send_begin_main_frame_funnel_;
 982   }
 983
 984   // If the active tree needs its first draw in any other state, we know the
 985   // main thread is in a high latency mode.
 986   return active_tree_needs_first_draw_;
 987 }
 988
 989 void SchedulerStateMachine::SetVisible(bool visible) { visible_ = visible; }
 990
 991 void SchedulerStateMachine::SetCanDraw(bool can_draw) { can_draw_ = can_draw; }
 992
 993 void SchedulerStateMachine::SetNeedsRedraw() { needs_redraw_ = true; }
 994
 995 void SchedulerStateMachine::SetNeedsAnimate() {
 996   needs_animate_ = true;
 997 }
 998
 999 void SchedulerStateMachine::SetWaitForReadyToDraw() {
1000   DCHECK(settings_.impl_side_painting);
1001   wait_for_active_tree_ready_to_draw_ = true;
1002 }
1003
1004 void SchedulerStateMachine::SetNeedsPrepareTiles() {
1005   if (!needs_prepare_tiles_) {
1006     TRACE_EVENT0("cc", "SchedulerStateMachine::SetNeedsPrepareTiles");
1007     needs_prepare_tiles_ = true;
1008   }
1009 }
1010
1011 void SchedulerStateMachine::SetMaxSwapsPending(int max) {
1012   max_pending_swaps_ = max;
1013 }
1014
1015 void SchedulerStateMachine::DidSwapBuffers() {
1016   pending_swaps_++;
1017   DCHECK_LE(pending_swaps_, max_pending_swaps_);
1018
1019   did_perform_swap_in_last_draw_ = true;
1020   last_frame_number_swap_performed_ = current_frame_number_;
1021 }
1022
1023 void SchedulerStateMachine::DidSwapBuffersComplete() {
1024   DCHECK_GT(pending_swaps_, 0);
1025   pending_swaps_--;
1026 }
1027
1028 void SchedulerStateMachine::SetImplLatencyTakesPriority(
1029     bool impl_latency_takes_priority) {
1030   impl_latency_takes_priority_ = impl_latency_takes_priority;
1031 }
1032
1033 void SchedulerStateMachine::DidDrawIfPossibleCompleted(DrawResult result) {
1034   switch (result) {
1035     case INVALID_RESULT:
1036       NOTREACHED() << "Uninitialized DrawResult.";
1037       break;
1038     case DRAW_ABORTED_CANT_DRAW:
1039     case DRAW_ABORTED_CONTEXT_LOST:
1040       NOTREACHED() << "Invalid return value from DrawAndSwapIfPossible:"
1041                    << result;
1042       break;
1043     case DRAW_SUCCESS:
1044       consecutive_checkerboard_animations_ = 0;
1045       forced_redraw_state_ = FORCED_REDRAW_STATE_IDLE;
1046       break;
1047     case DRAW_ABORTED_CHECKERBOARD_ANIMATIONS:
1048       needs_redraw_ = true;
1049
1050       // If we're already in the middle of a redraw, we don't need to
1051       // restart it.
1052       if (forced_redraw_state_ != FORCED_REDRAW_STATE_IDLE)
1053         return;
1054
1055       needs_commit_ = true;
1056       consecutive_checkerboard_animations_++;
1057       if (settings_.timeout_and_draw_when_animation_checkerboards &&
1058           consecutive_checkerboard_animations_ >=
1059               settings_.maximum_number_of_failed_draws_before_draw_is_forced_) {
1060         consecutive_checkerboard_animations_ = 0;
1061         // We need to force a draw, but it doesn't make sense to do this until
1062         // we've committed and have new textures.
1063         forced_redraw_state_ = FORCED_REDRAW_STATE_WAITING_FOR_COMMIT;
1064       }
1065       break;
1066     case DRAW_ABORTED_MISSING_HIGH_RES_CONTENT:
1067       // It's not clear whether this missing content is because of missing
1068       // pictures (which requires a commit) or because of memory pressure
1069       // removing textures (which might not).  To be safe, request a commit
1070       // anyway.
1071       needs_commit_ = true;
1072       break;
1073   }
1074 }
1075
1076 void SchedulerStateMachine::SetNeedsCommit() {
1077   needs_commit_ = true;
1078 }
1079
1080 void SchedulerStateMachine::NotifyReadyToCommit() {
1081   DCHECK(commit_state_ == COMMIT_STATE_BEGIN_MAIN_FRAME_STARTED)
1082       << AsValue()->ToString();
1083   commit_state_ = COMMIT_STATE_READY_TO_COMMIT;
1084   // In main thread low latency mode, commit should happen right after
1085   // BeginFrame, meaning when this function is called, next action should be
1086   // commit.
1087   if (settings_.main_thread_should_always_be_low_latency)
1088     DCHECK(ShouldCommit());
1089 }
1090
1091 void SchedulerStateMachine::BeginMainFrameAborted(CommitEarlyOutReason reason) {
1092   DCHECK_EQ(commit_state_, COMMIT_STATE_BEGIN_MAIN_FRAME_SENT);
1093   switch (reason) {
1094     case CommitEarlyOutReason::ABORTED_OUTPUT_SURFACE_LOST:
1095     case CommitEarlyOutReason::ABORTED_NOT_VISIBLE:
1096     case CommitEarlyOutReason::ABORTED_DEFERRED_COMMIT:
1097       commit_state_ = COMMIT_STATE_IDLE;
1098       SetNeedsCommit();
1099       return;
1100     case CommitEarlyOutReason::FINISHED_NO_UPDATES:
1101       bool commit_has_no_updates = true;
1102       UpdateStateOnCommit(commit_has_no_updates);
1103       return;
1104   }
1105 }
1106
1107 void SchedulerStateMachine::DidPrepareTiles() {
1108   needs_prepare_tiles_ = false;
1109   // "Fill" the PrepareTiles funnel.
1110   prepare_tiles_funnel_++;
1111 }
1112
1113 void SchedulerStateMachine::DidLoseOutputSurface() {
1114   if (output_surface_state_ == OUTPUT_SURFACE_LOST ||
1115       output_surface_state_ == OUTPUT_SURFACE_CREATING)
1116     return;
1117   output_surface_state_ = OUTPUT_SURFACE_LOST;
1118   needs_redraw_ = false;
1119   wait_for_active_tree_ready_to_draw_ = false;
1120 }
1121
1122 void SchedulerStateMachine::NotifyReadyToActivate() {
1123   if (has_pending_tree_)
1124     pending_tree_is_ready_for_activation_ = true;
1125 }
1126
1127 void SchedulerStateMachine::NotifyReadyToDraw() {
1128   wait_for_active_tree_ready_to_draw_ = false;
1129 }
1130
1131 void SchedulerStateMachine::DidCreateAndInitializeOutputSurface() {
1132   DCHECK_EQ(output_surface_state_, OUTPUT_SURFACE_CREATING);
1133   output_surface_state_ = OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT;
1134
1135   if (did_create_and_initialize_first_output_surface_) {
1136     // TODO(boliu): See if we can remove this when impl-side painting is always
1137     // on. Does anything on the main thread need to update after recreate?
1138     needs_commit_ = true;
1139   }
1140   did_create_and_initialize_first_output_surface_ = true;
1141   pending_swaps_ = 0;
1142 }
1143
1144 void SchedulerStateMachine::NotifyBeginMainFrameStarted() {
1145   DCHECK_EQ(commit_state_, COMMIT_STATE_BEGIN_MAIN_FRAME_SENT);
1146   commit_state_ = COMMIT_STATE_BEGIN_MAIN_FRAME_STARTED;
1147 }
1148
1149 bool SchedulerStateMachine::HasInitializedOutputSurface() const {
1150   switch (output_surface_state_) {
1151     case OUTPUT_SURFACE_LOST:
1152     case OUTPUT_SURFACE_CREATING:
1153       return false;
1154
1155     case OUTPUT_SURFACE_ACTIVE:
1156     case OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT:
1157     case OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION:
1158       return true;
1159   }
1160   NOTREACHED();
1161   return false;
1162 }
1163
1164 std::string SchedulerStateMachine::GetStatesForDebugging() const {
1165   return base::StringPrintf("%c %d %d %d %c %c %c %d %d",
1166       needs_commit_ ? 'T' : 'F',
1167       static_cast<int>(output_surface_state_),
1168       static_cast<int>(begin_impl_frame_state_),
1169       static_cast<int>(commit_state_),
1170       has_pending_tree_ ? 'T' : 'F',
1171       pending_tree_is_ready_for_activation_ ? 'T' : 'F',
1172       active_tree_needs_first_draw_ ? 'T' : 'F',
1173       max_pending_swaps_,
1174       pending_swaps_);
1175 }
1176
1177 }  // namespace cc