cc: Control defer_commits logic by Scheduler

cc/scheduler/scheduler_state_machine.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/scheduler/scheduler_state_machine.h"
 
 #include "base/debug/trace_event.h"
 #include "base/debug/trace_event_argument.h"
 #include "base/format_macros.h"
 #include "base/logging.h"
@@ skipping 31 matching lines @@
       can_draw_(false),
       has_pending_tree_(false),
       pending_tree_is_ready_for_activation_(false),
       active_tree_needs_first_draw_(false),
       did_commit_after_animating_(false),
       did_create_and_initialize_first_output_surface_(false),
       impl_latency_takes_priority_(false),
       skip_next_begin_main_frame_to_reduce_latency_(false),
       skip_begin_main_frame_to_reduce_latency_(false),
       continuous_painting_(false),
-      impl_latency_takes_priority_on_battery_(false) {
+      impl_latency_takes_priority_on_battery_(false),
+      defer_commits_(false) {
 }
 
 const char* SchedulerStateMachine::OutputSurfaceStateToString(
     OutputSurfaceState state) {
   switch (state) {
     case OUTPUT_SURFACE_ACTIVE:
       return "OUTPUT_SURFACE_ACTIVE";
     case OUTPUT_SURFACE_LOST:
       return "OUTPUT_SURFACE_LOST";
     case OUTPUT_SURFACE_CREATING:
@@ skipping 171 matching lines @@
                     impl_latency_takes_priority_);
   state->SetBoolean("main_thread_is_in_high_latency_mode",
                     MainThreadIsInHighLatencyMode());
   state->SetBoolean("skip_begin_main_frame_to_reduce_latency",
                     skip_begin_main_frame_to_reduce_latency_);
   state->SetBoolean("skip_next_begin_main_frame_to_reduce_latency",
                     skip_next_begin_main_frame_to_reduce_latency_);
   state->SetBoolean("continuous_painting", continuous_painting_);
   state->SetBoolean("impl_latency_takes_priority_on_battery",
                     impl_latency_takes_priority_on_battery_);
+  state->SetBoolean("defer_commits", defer_commits_);
   state->EndDictionary();
 }
 
 void SchedulerStateMachine::AdvanceCurrentFrameNumber() {
   current_frame_number_++;
 
   // "Drain" the ManageTiles funnel.
   if (manage_tiles_funnel_ > 0)
     manage_tiles_funnel_--;
 
@@ skipping 181 matching lines @@
 }
 
 bool SchedulerStateMachine::CouldSendBeginMainFrame() const {
   if (!needs_commit_)
     return false;
 
   // We can not perform commits if we are not visible.
   if (!visible_)
     return false;
 
+  // We do not need new commits if it is deferred.
+  if (defer_commits_)
+    return false;
+
   return true;
 }
 
 bool SchedulerStateMachine::ShouldSendBeginMainFrame() const {
   if (!CouldSendBeginMainFrame())
     return false;
 
   // Only send BeginMainFrame when there isn't another commit pending already.
   if (commit_state_ != COMMIT_STATE_IDLE)
     return false;
@@ skipping 292 matching lines @@
 // Note: If SupportsProactiveBeginFrame is false, the scheduler should poll
 // for changes in it's draw state so it can request a BeginFrame when it's
 // actually ready.
 bool SchedulerStateMachine::SupportsProactiveBeginFrame() const {
   // It is undesirable to proactively request BeginFrames if we are
   // using a synchronous compositor because we *must* draw for every
   // BeginFrame, which could cause duplicate draws.
   return !settings_.using_synchronous_renderer_compositor;
 }
 
+void SchedulerStateMachine::SetDeferCommits(bool defer_commits) {
+  defer_commits_ = defer_commits;
+}
+
 // These are the cases where we definitely (or almost definitely) have a
 // new frame to animate and/or draw and can draw.
 bool SchedulerStateMachine::BeginFrameNeededToAnimateOrDraw() const {
   // The output surface is the provider of BeginImplFrames, so we are not going
   // to get them even if we ask for them.
   if (!HasInitializedOutputSurface())
     return false;
 
+  // New BeginFrame should not be triggered during the commit is deferred.
+  if (defer_commits_)

[danakj, 2014/11/19 16:31:33]

Why is the ShouldSendBeginMainFrame() change not enough? Doesn't that happen
before calling this always?

[brianderson, 2014/11/19 19:55:07]

Agree that this check isn't needed. Deferring commit should prevent us from
needing to animate or draw. Also, if for some reason we _did_ need to draw the
active tree but wanted to defer commits, we'll need BeginFrames to draw the
active tree.

[simonhong, 2014/11/26 15:52:53]

Yep, I think you're right.
Deferring commit should not prevent BeginFrame triggering.

+    return false;
+
   // The forced draw respects our normal draw scheduling, so we need to
   // request a BeginImplFrame for it.
   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
     return true;
 
   // We need to draw a more complete frame than we did the last BeginImplFrame,
   // so request another BeginImplFrame in anticipation that we will have
   // additional visible tiles.
   if (swap_used_incomplete_tile_)
     return true;
 
   return needs_animate_ || needs_redraw_;
 }
 
 // These are cases where we are very likely to draw soon, but might not
 // actually have a new frame to draw when we receive the next BeginImplFrame.
 // Proactively requesting the BeginImplFrame helps hide the round trip latency
 // of the SetNeedsBeginFrame request that has to go to the Browser.
 bool SchedulerStateMachine::ProactiveBeginFrameWanted() const {
   // The output surface is the provider of BeginImplFrames,
   // so we are not going to get them even if we ask for them.
   if (!HasInitializedOutputSurface())
     return false;
 
   // Do not be proactive when invisible.
   if (!visible_)
     return false;
 
+  // New BeginFrame should not be triggered during the commit is deferred.

[danakj, 2014/11/19 16:31:33]

ditto?

[brianderson, 2014/11/19 19:55:07]

ditto.

[simonhong, 2014/11/26 15:52:53]

Done.

+  if (defer_commits_)
+    return false;
+
   // We should proactively request a BeginImplFrame if a commit is pending
   // because we will want to draw if the commit completes quickly.
   if (needs_commit_ || commit_state_ != COMMIT_STATE_IDLE)
     return true;
 
   // If the pending tree activates quickly, we'll want a BeginImplFrame soon
   // to draw the new active tree.
   if (has_pending_tree_)
     return true;
 
@@ skipping 298 matching lines @@
       static_cast<int>(begin_impl_frame_state_),
       static_cast<int>(commit_state_),
       has_pending_tree_ ? 'T' : 'F',
       pending_tree_is_ready_for_activation_ ? 'T' : 'F',
       active_tree_needs_first_draw_ ? 'T' : 'F',
       max_pending_swaps_,
       pending_swaps_);
 }
 
 }  // namespace cc