cc: Allow the main thread to cancel commits

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/format_macros.h"
 #include "base/logging.h"
 #include "base/strings/stringprintf.h"
 
 namespace cc {
 
 SchedulerStateMachine::SchedulerStateMachine(const SchedulerSettings& settings)
     : settings_(settings),
       commit_state_(COMMIT_STATE_IDLE),
       commit_count_(0),
       current_frame_number_(0),
+      last_frame_number_where_begin_frame_sent_to_main_thread_(-1),
       last_frame_number_where_draw_was_called_(-1),
       last_frame_number_where_tree_activation_attempted_(-1),
       last_frame_number_where_check_for_completed_tile_uploads_called_(-1),
       consecutive_failed_draws_(0),
       maximum_number_of_failed_draws_before_draw_is_forced_(3),
       needs_redraw_(false),
       swap_used_incomplete_tile_(false),
       needs_forced_redraw_(false),
       needs_forced_redraw_after_next_commit_(false),
       needs_commit_(false),
@@ skipping 149 matching lines @@
   if (!BeginFrameNeededToDrawByImplThread())
     return true;
   return false;
 }
 
 SchedulerStateMachine::Action SchedulerStateMachine::NextAction() const {
   if (ShouldAcquireLayerTexturesForMainThread())
     return ACTION_ACQUIRE_LAYER_TEXTURES_FOR_MAIN_THREAD;
 
   switch (commit_state_) {
-    case COMMIT_STATE_IDLE:
+    case COMMIT_STATE_IDLE: {
       if (output_surface_state_ != OUTPUT_SURFACE_ACTIVE &&
           needs_forced_redraw_)
         return ACTION_DRAW_FORCED;
       if (output_surface_state_ != OUTPUT_SURFACE_ACTIVE &&
           needs_forced_commit_)
         // TODO(enne): Should probably drop the active tree on force commit.
         return has_pending_tree_ ? ACTION_NONE
                                  : ACTION_SEND_BEGIN_FRAME_TO_MAIN_THREAD;
       if (output_surface_state_ == OUTPUT_SURFACE_LOST && can_start_)
         return ACTION_BEGIN_OUTPUT_SURFACE_CREATION;
       if (output_surface_state_ == OUTPUT_SURFACE_CREATING)
         return ACTION_NONE;
       if (ShouldCheckForCompletedTileUploads())
         return ACTION_CHECK_FOR_COMPLETED_TILE_UPLOADS;
       if (ShouldAttemptTreeActivation())
         return ACTION_ACTIVATE_PENDING_TREE_IF_NEEDED;
       if (ShouldDraw()) {
         return needs_forced_redraw_ ? ACTION_DRAW_FORCED
                                     : ACTION_DRAW_IF_POSSIBLE;
       }
-      if (needs_commit_ &&
-          ((visible_ && output_surface_state_ == OUTPUT_SURFACE_ACTIVE)
-           || needs_forced_commit_))
+      bool can_commit_this_frame =
+          visible_ &&
+          current_frame_number_ >
+              last_frame_number_where_begin_frame_sent_to_main_thread_;
+      if (needs_commit_ && ((can_commit_this_frame &&
+                             output_surface_state_ == OUTPUT_SURFACE_ACTIVE) ||
+                            needs_forced_commit_))
         // TODO(enne): Should probably drop the active tree on force commit.
         return has_pending_tree_ ? ACTION_NONE
                                  : ACTION_SEND_BEGIN_FRAME_TO_MAIN_THREAD;
       return ACTION_NONE;
-
+    }
     case COMMIT_STATE_FRAME_IN_PROGRESS:
       if (ShouldCheckForCompletedTileUploads())
         return ACTION_CHECK_FOR_COMPLETED_TILE_UPLOADS;
       if (ShouldAttemptTreeActivation())
         return ACTION_ACTIVATE_PENDING_TREE_IF_NEEDED;
       if (ShouldDraw()) {
         return needs_forced_redraw_ ? ACTION_DRAW_FORCED
                                     : ACTION_DRAW_IF_POSSIBLE;
       }
       return ACTION_NONE;
 
     case COMMIT_STATE_READY_TO_COMMIT:
       return ACTION_COMMIT;
 
     case COMMIT_STATE_WAITING_FOR_FIRST_DRAW: {
       if (ShouldCheckForCompletedTileUploads())
         return ACTION_CHECK_FOR_COMPLETED_TILE_UPLOADS;
       if (ShouldAttemptTreeActivation())
         return ACTION_ACTIVATE_PENDING_TREE_IF_NEEDED;
       if (ShouldDraw() || output_surface_state_ == OUTPUT_SURFACE_LOST) {
         return needs_forced_redraw_ ? ACTION_DRAW_FORCED
                                     : ACTION_DRAW_IF_POSSIBLE;
       }
       // COMMIT_STATE_WAITING_FOR_FIRST_DRAW wants to enforce a draw. If
       // can_draw_ is false or textures are not available, proceed to the next
       // step (similar as in COMMIT_STATE_IDLE).
-      bool can_commit = visible_ || needs_forced_commit_;
+      bool can_commit =
+          needs_forced_commit_ ||
+          (visible_ &&
+           current_frame_number_ >

[enne (OOO), 2013/07/16 00:15:18]

Added this frame check here as well, as it was causing my DCHECKs in
UpdateState(ACTION_SEND_BEGIN_FRAME_TO_MAIN_THREAD) to trigger in
SchedulerTest.VisibilitySwitchWithTextureAcquisition.

+               last_frame_number_where_begin_frame_sent_to_main_thread_);
       if (needs_commit_ && can_commit && DrawSuspendedUntilCommit())
         return has_pending_tree_ ? ACTION_NONE
                                  : ACTION_SEND_BEGIN_FRAME_TO_MAIN_THREAD;
       return ACTION_NONE;
     }
 
     case COMMIT_STATE_WAITING_FOR_FIRST_FORCED_DRAW:
       if (ShouldCheckForCompletedTileUploads())
         return ACTION_CHECK_FOR_COMPLETED_TILE_UPLOADS;
       if (ShouldAttemptTreeActivation())
@@ skipping 16 matching lines @@
           current_frame_number_;
       return;
 
     case ACTION_ACTIVATE_PENDING_TREE_IF_NEEDED:
       last_frame_number_where_tree_activation_attempted_ =
           current_frame_number_;
       return;
 
     case ACTION_SEND_BEGIN_FRAME_TO_MAIN_THREAD:
       DCHECK(!has_pending_tree_);
-      DCHECK(visible_ || needs_forced_commit_);
+      if (!needs_forced_commit_) {
+        DCHECK(visible_);
+        DCHECK_GT(current_frame_number_,
+                  last_frame_number_where_begin_frame_sent_to_main_thread_);
+      }
       commit_state_ = COMMIT_STATE_FRAME_IN_PROGRESS;
       needs_commit_ = false;
       needs_forced_commit_ = false;
+      last_frame_number_where_begin_frame_sent_to_main_thread_ =
+          current_frame_number_;
       return;
 
     case ACTION_COMMIT:
       commit_count_++;
       if (expect_immediate_begin_frame_for_main_thread_)
         commit_state_ = COMMIT_STATE_WAITING_FOR_FIRST_FORCED_DRAW;
       else
         commit_state_ = COMMIT_STATE_WAITING_FOR_FIRST_DRAW;
       // When impl-side painting, we draw on activation instead of on commit.
       if (!settings_.impl_side_painting)
@@ skipping 67 matching lines @@
   if (!visible_ || output_surface_state_ != OUTPUT_SURFACE_ACTIVE)
     return false;
 
   // We should proactively request a BeginFrame if a commit or a tree activation
   // is pending.
   return (needs_commit_ || needs_forced_commit_ ||
           commit_state_ != COMMIT_STATE_IDLE || has_pending_tree_);
 }
 
 void SchedulerStateMachine::DidEnterBeginFrame(const BeginFrameArgs& args) {
+  current_frame_number_++;

[enne (OOO), 2013/07/16 00:15:18]

I moved this here, which seemed more natural and also got rid of the changes to
the scheduler state machine unit tests.

[danakj, 2013/07/17 20:53:24]

This means that functions like
SchedulerStateMachine::HasCheckedForCompletedTileUploadsThisFrame() suddenly
become false as soon as we enter begin frame, instead of when we leave.

I think the side effect of this means that things like checking for tile uploads
will /always/ happen inside BeginFrame instead of sometimes outside. Which means
that when we EnterBeginFrame, we'll do a check before drawing now, since it has
higher priority. Before, we would have done the check for completed uploads
after LeaveBeginFrame if some state changed and caused us to pump the scheduler.
Or, before the draw if nothing managed to pump the scheduler before the next
BeginFrame.

I guess we have no unit test to verify that this does *not* happen, so it's
probably okay? I just want to make sure this side effect is intentional.

[enne (OOO), 2013/07/18 17:36:37]

Although there are some side effects here, I think it is the correct thing to
do.  If you don't, then after Scheduler::BeginFrame, you won't get any calls for
things that were waiting on a new frame, like sending a begin frame message and
you have to (bizarrely) wait for some other state change on the state machine to
get that action to happen.

brianderson, can you take a look at this change and tell me what you think?

[brianderson, 2013/07/18 18:30:34]

Incrementing the current_frame_number_ here is definitely more natural. We are
starting a new frame, so we should reset all the things we need to try.

In https://codereview.chromium.org/16871016/, I have a counter for the number of
times we enter BeginFrame and the number of times we hit the deadline but
couldn't find a use for the deadline count.

   inside_begin_frame_ = true;
   last_begin_frame_args_ = args;
 }
 
 void SchedulerStateMachine::DidLeaveBeginFrame() {
-  current_frame_number_++;
   inside_begin_frame_ = false;
 }
 
 void SchedulerStateMachine::SetVisible(bool visible) { visible_ = visible; }
 
 void SchedulerStateMachine::SetNeedsRedraw() { needs_redraw_ = true; }
 
 void SchedulerStateMachine::DidSwapUseIncompleteTile() {
   swap_used_incomplete_tile_ = true;
 }
@@ skipping 29 matching lines @@
 }
 
 void SchedulerStateMachine::FinishCommit() {
   DCHECK(commit_state_ == COMMIT_STATE_FRAME_IN_PROGRESS ||
          (expect_immediate_begin_frame_for_main_thread_ &&
           commit_state_ != COMMIT_STATE_IDLE))
       << ToString();
   commit_state_ = COMMIT_STATE_READY_TO_COMMIT;
 }
 
-void SchedulerStateMachine::BeginFrameAbortedByMainThread() {
+void SchedulerStateMachine::BeginFrameAbortedByMainThread(bool did_handle) {
   DCHECK_EQ(commit_state_, COMMIT_STATE_FRAME_IN_PROGRESS);
   if (expect_immediate_begin_frame_for_main_thread_) {
     expect_immediate_begin_frame_for_main_thread_ = false;
+  } else if (did_handle) {
+    commit_state_ = COMMIT_STATE_IDLE;
   } else {
     commit_state_ = COMMIT_STATE_IDLE;
     SetNeedsCommit();
   }
 }
 
 void SchedulerStateMachine::DidLoseOutputSurface() {
   if (output_surface_state_ == OUTPUT_SURFACE_LOST ||
       output_surface_state_ == OUTPUT_SURFACE_CREATING)
     return;
@@ skipping 25 matching lines @@
 bool SchedulerStateMachine::HasInitializedOutputSurface() const {
   return output_surface_state_ == OUTPUT_SURFACE_ACTIVE;
 }
 
 void SchedulerStateMachine::SetMaximumNumberOfFailedDrawsBeforeDrawIsForced(
     int num_draws) {
   maximum_number_of_failed_draws_before_draw_is_forced_ = num_draws;
 }
 
 }  // namespace cc