cc: Implement unified BeginFrame on aura

ui/compositor/compositor.cc

 // Copyright (c) 2012 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 "ui/compositor/compositor.h"
 
 #include <algorithm>
 #include <deque>
 
 #include "base/bind.h"
@@ skipping 76 matching lines @@
   // When impl-side painting is enabled, this will ensure PictureLayers always
   // can have LCD text, to match the previous behaviour with ContentLayers,
   // where LCD-not-allowed notifications were ignored.
   settings.layers_always_allowed_lcd_text = true;
   settings.renderer_settings.refresh_rate =
       context_factory_->DoesCreateTestContexts() ? kTestRefreshRate
                                                  : kDefaultRefreshRate;
   settings.main_frame_before_activation_enabled = false;
   settings.throttle_frame_production =
       !command_line->HasSwitch(switches::kDisableGpuVsync);
+  settings.forward_begin_frames_to_children =
+      command_line->HasSwitch(cc::switches::kEnableBeginFrameScheduling);
 #if !defined(OS_MACOSX)
   settings.renderer_settings.partial_swap_enabled =
       !command_line->HasSwitch(cc::switches::kUIDisablePartialSwap);
 #endif
 #if defined(OS_CHROMEOS)
   settings.per_tile_painting_enabled = true;
 #endif
 #if defined(OS_WIN)
   settings.disable_hi_res_timer_tasks_on_battery =
       !context_factory_->DoesCreateTestContexts();
@@ skipping 23 matching lines @@
       command_line->HasSwitch(cc::switches::kUIShowNonOccludingRects);
 
   settings.initial_debug_state.SetRecordRenderingStats(
       command_line->HasSwitch(cc::switches::kEnableGpuBenchmarking));
 
   settings.impl_side_painting = IsUIImplSidePaintingEnabled();
   settings.use_zero_copy = IsUIZeroCopyEnabled();
 
   base::TimeTicks before_create = base::TimeTicks::Now();
   if (compositor_thread_loop_.get()) {
+    // Unified BeginFrame scheduling shouldn't be enabled with threaded
+    // compositing.
+    DCHECK(!settings.forward_begin_frames_to_children);
     host_ = cc::LayerTreeHost::CreateThreaded(
         this,
         context_factory_->GetSharedBitmapManager(),
         context_factory_->GetGpuMemoryBufferManager(),
         settings,
         task_runner_,
         compositor_thread_loop_,
         nullptr);
   } else {
     host_ = cc::LayerTreeHost::CreateSingleThreaded(
@@ skipping 11 matching lines @@
   host_->set_surface_id_namespace(surface_id_allocator_->id_namespace());
   host_->SetLayerTreeHostClientReady();
 }
 
 Compositor::~Compositor() {
   TRACE_EVENT0("shutdown", "Compositor::destructor");
 
   CancelCompositorLock();
   DCHECK(!compositor_lock_);
 
+  DCHECK(!begin_frame_observer_list_.might_have_observers());
+
   if (root_layer_)
     root_layer_->SetCompositor(NULL);
 
   // Stop all outstanding draws before telling the ContextFactory to tear
   // down any contexts that the |host_| may rely upon.
   host_.reset();
 
   context_factory_->RemoveCompositor(this);
 }
 
@@ skipping 114 matching lines @@
 void Compositor::RemoveAnimationObserver(
     CompositorAnimationObserver* observer) {
   animation_observer_list_.RemoveObserver(observer);
 }
 
 bool Compositor::HasAnimationObserver(
     const CompositorAnimationObserver* observer) const {
   return animation_observer_list_.HasObserver(observer);
 }
 
+void Compositor::AddBeginFrameObserver(
+    CompositorBeginFrameObserver* observer,
+    const cc::BeginFrameArgs& last_begin_frame_args_sent_to_observer) {
+  // If |last_begin_frame_args_| is still effective, send it to the new
+  // |observer| immediately.
+  if (!last_begin_frame_args_sent_to_observer.deadline.is_null() &&
+      last_begin_frame_args_sent_to_observer != missed_begin_frame_args_) {
+    missed_begin_frame_args_.type = cc::BeginFrameArgs::MISSED;
+    observer->OnSendBeginFrame(missed_begin_frame_args_);

[mithro-old, 2014/12/16 10:50:58]

I don't think this is correct, if the observer was a proper BeginFrameObserver
the code would read something like;

if (!new_args.IsValid())
  return;

// If the last begin frame is invalid, then any new begin frame is valid.
if (observer->LastUsedBeginFrameArgs().IsValid())
  OnSendBeginFrame(new_args);

// Only allow new args have a *strictly bigger* frame_time value
if (new_args.frame_time >= observer->LastUsedBeginFrameArgs().frame_time)
  OnSendBeginFrame(new_args);

[simonhong, 2014/12/16 15:13:30]

This code can be effective when observer is removed and added again and
|missed_begin_frame_args_| is still effective.
In this case, |missed_begin_frame_args_| can be delivered immediately to
renderer.
Of course, |missed_begin_frame_args_| 's deadline can be passed.
I and brian thought that this can be handled in the Scheduler side.
Old BeginFrameArgs with MISSED type will be dropped by RetroFrame handler.
So we are sending |missed_begin_frame_args_| to renderer without much
inspection.

[brianderson, 2014/12/16 23:23:52]

@mithro's suggestion enforces monotonicity of the frame_time, which is
important, especially now that the latest patch sends a fake BeginFrame for the
first frame of dev tools.

Before the dev tools change, I think the guarantee of monotonicity from the
scheduler's begin frame source would have been good enough.

+  }
+
+  if (!begin_frame_observer_list_.might_have_observers())
+    SetChildrenNeedBeginFrames(true);
+  begin_frame_observer_list_.AddObserver(observer);
+}
+
+void Compositor::RemoveBeginFrameObserver(
+    CompositorBeginFrameObserver* observer) {
+  DCHECK(begin_frame_observer_list_.HasObserver(observer));
+  begin_frame_observer_list_.RemoveObserver(observer);
+
+  if (!begin_frame_observer_list_.might_have_observers())
+    SetChildrenNeedBeginFrames(false);
+}
+
 void Compositor::BeginMainFrame(const cc::BeginFrameArgs& args) {
   FOR_EACH_OBSERVER(CompositorAnimationObserver,
                     animation_observer_list_,
                     OnAnimationStep(args.frame_time));
   if (animation_observer_list_.might_have_observers())
     host_->SetNeedsAnimate();
 }
 
 void Compositor::Layout() {
   // We're sending damage that will be addressed during this composite
@@ skipping 37 matching lines @@
   FOR_EACH_OBSERVER(CompositorObserver, observer_list_,
                     OnCompositingStarted(this, start_time));
 }
 
 void Compositor::DidAbortSwapBuffers() {
   FOR_EACH_OBSERVER(CompositorObserver,
                     observer_list_,
                     OnCompositingAborted(this));
 }
 
+void Compositor::SendBeginFramesToChildren(const cc::BeginFrameArgs& args) {
+  FOR_EACH_OBSERVER(CompositorBeginFrameObserver,
+                    begin_frame_observer_list_,
+                    OnSendBeginFrame(args));
+  missed_begin_frame_args_ = args;
+}
+
 const cc::LayerTreeDebugState& Compositor::GetLayerTreeDebugState() const {
   return host_->debug_state();
 }
 
 void Compositor::SetLayerTreeDebugState(
     const cc::LayerTreeDebugState& debug_state) {
   host_->SetDebugState(debug_state);
 }
 
 const cc::RendererSettings& Compositor::GetRendererSettings() const {
@@ skipping 18 matching lines @@
   FOR_EACH_OBSERVER(CompositorObserver,
                     observer_list_,
                     OnCompositingLockStateChanged(this));
 }
 
 void Compositor::CancelCompositorLock() {
   if (compositor_lock_)
     compositor_lock_->CancelLock();
 }
 
+void Compositor::SetChildrenNeedBeginFrames(bool need_begin_frames) {
+  host_->SetChildrenNeedBeginFrames(need_begin_frames);
+}
+
 }  // namespace ui