Refactoring the way begin frame sources inside scheduler work.

This change;
 * Makes non-vsync aligned rendering just another begin frame source.
 * Makes it easier to add vsync/begin frame stabilisation / filtering in the future.

This CL no longer moves background ticking into the scheduler rather than the LayerTreeHostImpl, that will occur in a later CL.

BUG=345459

Review URL: https://codereview.chromium.org/267783004

Cr-Commit-Position: refs/heads/master@{#297389}

1 files changed, 491 insertions, 0 deletions

diff --git a/cc/scheduler/begin_frame_source.cc b/cc/scheduler/begin_frame_source.cc
new file mode 100644
index 0000000..a5d859f
--- /dev/null
+++ b/cc/scheduler/begin_frame_source.cc
@@ -0,0 +1,491 @@
+// Copyright 2014 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/begin_frame_source.h"
+
+#include "base/auto_reset.h"
+#include "base/debug/trace_event.h"
+#include "base/debug/trace_event_argument.h"
+#include "base/logging.h"
+#include "base/strings/string_number_conversions.h"
+#include "cc/scheduler/delay_based_time_source.h"
+#include "cc/scheduler/scheduler.h"
+#include "ui/gfx/frame_time.h"
+
+#ifdef NDEBUG
+#define DEBUG_FRAMES(...)
+#else
+#define DEBUG_FRAMES(name, arg1_name, arg1_val, arg2_name, arg2_val)   \
+  TRACE_EVENT2(TRACE_DISABLED_BY_DEFAULT("cc.debug.scheduler.frames"), \
+               name,                                                   \
+               arg1_name,                                              \
+               arg1_val,                                               \
+               arg2_name,                                              \
+               arg2_val);
+#endif
+
+namespace cc {
+
+// BeginFrameObserverMixIn -----------------------------------------------
+BeginFrameObserverMixIn::BeginFrameObserverMixIn()
+    : last_begin_frame_args_(), dropped_begin_frame_args_(0) {
+}
+
+const BeginFrameArgs BeginFrameObserverMixIn::LastUsedBeginFrameArgs() const {
+  return last_begin_frame_args_;
+}
+void BeginFrameObserverMixIn::OnBeginFrame(const BeginFrameArgs& args) {
+  DEBUG_FRAMES("BeginFrameObserverMixIn::OnBeginFrame",
+               "last args",
+               last_begin_frame_args_.AsValue(),
+               "new args",
+               args.AsValue());
+  DCHECK(args.IsValid());
+  DCHECK(args.frame_time >= last_begin_frame_args_.frame_time);
+  bool used = OnBeginFrameMixInDelegate(args);
+  if (used) {
+    last_begin_frame_args_ = args;
+  } else {
+    ++dropped_begin_frame_args_;
+  }
+}
+
+void BeginFrameObserverMixIn::AsValueInto(
+    base::debug::TracedValue* dict) const {
+  dict->BeginDictionary("last_begin_frame_args_");
+  last_begin_frame_args_.AsValueInto(dict);
+  dict->EndDictionary();
+  dict->SetInteger("dropped_begin_frame_args_", dropped_begin_frame_args_);
+}
+
+// BeginFrameSourceMixIn ------------------------------------------------------
+BeginFrameSourceMixIn::BeginFrameSourceMixIn()
+    : observer_(NULL),
+      needs_begin_frames_(false),
+      inside_as_value_into_(false) {
+  DCHECK(!observer_);
+  DCHECK_EQ(inside_as_value_into_, false);
+}
+
+bool BeginFrameSourceMixIn::NeedsBeginFrames() const {
+  return needs_begin_frames_;
+}
+
+void BeginFrameSourceMixIn::SetNeedsBeginFrames(bool needs_begin_frames) {
+  DEBUG_FRAMES("BeginFrameSourceMixIn::SetNeedsBeginFrames",
+               "current state",
+               needs_begin_frames_,
+               "new state",
+               needs_begin_frames);
+  if (needs_begin_frames_ != needs_begin_frames) {
+    OnNeedsBeginFramesChange(needs_begin_frames);
+  }
+  needs_begin_frames_ = needs_begin_frames;
+}
+
+void BeginFrameSourceMixIn::AddObserver(BeginFrameObserver* obs) {
+  DEBUG_FRAMES("BeginFrameSourceMixIn::AddObserver",
+               "current observer",
+               observer_,
+               "to add observer",
+               obs);
+  DCHECK(!observer_);
+  observer_ = obs;
+}
+
+void BeginFrameSourceMixIn::RemoveObserver(BeginFrameObserver* obs) {
+  DEBUG_FRAMES("BeginFrameSourceMixIn::RemoveObserver",
+               "current observer",
+               observer_,
+               "to remove observer",
+               obs);
+  DCHECK_EQ(observer_, obs);
+  observer_ = NULL;
+}
+
+void BeginFrameSourceMixIn::CallOnBeginFrame(const BeginFrameArgs& args) {
+  DEBUG_FRAMES("BeginFrameSourceMixIn::CallOnBeginFrame",
+               "current observer",
+               observer_,
+               "args",
+               args.AsValue());
+  if (observer_) {
+    return observer_->OnBeginFrame(args);
+  }
+}
+
+// Tracing support
+void BeginFrameSourceMixIn::AsValueInto(base::debug::TracedValue* dict) const {
+  // As the observer might try to trace the source, prevent an infinte loop
+  // from occuring.
+  if (inside_as_value_into_) {
+    dict->SetString("observer", "<loop detected>");
+    return;
+  }
+
+  if (observer_) {
+    base::AutoReset<bool> prevent_loops(
+        const_cast<bool*>(&inside_as_value_into_), true);
+    dict->BeginDictionary("observer");
+    observer_->AsValueInto(dict);
+    dict->EndDictionary();
+  } else {
+    dict->SetString("observer", "NULL");
+  }
+  dict->SetBoolean("needs_begin_frames", NeedsBeginFrames());
+}
+
+// BackToBackBeginFrameSourceMixIn --------------------------------------------
+scoped_ptr<BackToBackBeginFrameSource> BackToBackBeginFrameSource::Create(
+    base::SingleThreadTaskRunner* task_runner) {
+  return make_scoped_ptr(new BackToBackBeginFrameSource(task_runner));
+}
+
+BackToBackBeginFrameSource::BackToBackBeginFrameSource(
+    base::SingleThreadTaskRunner* task_runner)
+    : BeginFrameSourceMixIn(),
+      weak_factory_(this),
+      task_runner_(task_runner),
+      send_begin_frame_posted_(false) {
+  DCHECK(task_runner);
+  DCHECK_EQ(needs_begin_frames_, false);
+  DCHECK_EQ(send_begin_frame_posted_, false);
+}
+
+BackToBackBeginFrameSource::~BackToBackBeginFrameSource() {
+}
+
+base::TimeTicks BackToBackBeginFrameSource::Now() {
+  return gfx::FrameTime::Now();
+}
+
+void BackToBackBeginFrameSource::OnNeedsBeginFramesChange(
+    bool needs_begin_frames) {
+  if (!needs_begin_frames)
+    return;
+
+  if (send_begin_frame_posted_)
+    return;
+
+  send_begin_frame_posted_ = true;
+  task_runner_->PostTask(FROM_HERE,
+                         base::Bind(&BackToBackBeginFrameSource::BeginFrame,
+                                    weak_factory_.GetWeakPtr()));
+}
+
+void BackToBackBeginFrameSource::BeginFrame() {
+  send_begin_frame_posted_ = false;
+
+  if (!needs_begin_frames_)
+    return;
+
+  base::TimeTicks now = Now();
+  BeginFrameArgs args =
+      BeginFrameArgs::Create(now,
+                             now + BeginFrameArgs::DefaultInterval(),
+                             BeginFrameArgs::DefaultInterval());
+  CallOnBeginFrame(args);
+}
+
+// BeginFrameSource support
+
+void BackToBackBeginFrameSource::DidFinishFrame(size_t remaining_frames) {
+  if (remaining_frames == 0) {
+    OnNeedsBeginFramesChange(NeedsBeginFrames());
+  }
+}
+
+// Tracing support
+void BackToBackBeginFrameSource::AsValueInto(
+    base::debug::TracedValue* dict) const {
+  dict->SetString("type", "BackToBackBeginFrameSource");
+  BeginFrameSourceMixIn::AsValueInto(dict);
+  dict->SetBoolean("send_begin_frame_posted_", send_begin_frame_posted_);
+}
+
+// SyntheticBeginFrameSource ---------------------------------------------
+scoped_ptr<SyntheticBeginFrameSource> SyntheticBeginFrameSource::Create(
+    base::SingleThreadTaskRunner* task_runner,
+    base::TimeTicks initial_vsync_timebase,
+    base::TimeDelta initial_vsync_interval) {
+  scoped_refptr<DelayBasedTimeSource> time_source;
+  if (gfx::FrameTime::TimestampsAreHighRes()) {
+    time_source = DelayBasedTimeSourceHighRes::Create(initial_vsync_interval,
+                                                      task_runner);
+  } else {
+    time_source =
+        DelayBasedTimeSource::Create(initial_vsync_interval, task_runner);
+  }
+
+  return make_scoped_ptr(new SyntheticBeginFrameSource(time_source));
+}
+
+SyntheticBeginFrameSource::SyntheticBeginFrameSource(
+    scoped_refptr<DelayBasedTimeSource> time_source)
+    : BeginFrameSourceMixIn(), time_source_(time_source) {
+  time_source_->SetActive(false);
+  time_source_->SetClient(this);
+}
+
+SyntheticBeginFrameSource::~SyntheticBeginFrameSource() {
+  if (NeedsBeginFrames())
+    time_source_->SetActive(false);
+}
+
+void SyntheticBeginFrameSource::OnUpdateVSyncParameters(
+    base::TimeTicks new_vsync_timebase,
+    base::TimeDelta new_vsync_interval) {
+  time_source_->SetTimebaseAndInterval(new_vsync_timebase, new_vsync_interval);
+}
+
+BeginFrameArgs SyntheticBeginFrameSource::CreateBeginFrameArgs(
+    base::TimeTicks frame_time,
+    BeginFrameArgs::BeginFrameArgsType type) {
+  base::TimeTicks deadline = time_source_->NextTickTime();
+  return BeginFrameArgs::CreateTyped(
+      frame_time, deadline, time_source_->Interval(), type);
+}
+
+// TimeSourceClient support
+void SyntheticBeginFrameSource::OnTimerTick() {
+  CallOnBeginFrame(CreateBeginFrameArgs(time_source_->LastTickTime(),
+                                        BeginFrameArgs::NORMAL));
+}
+
+// BeginFrameSourceMixIn support
+void SyntheticBeginFrameSource::OnNeedsBeginFramesChange(
+    bool needs_begin_frames) {
+  base::TimeTicks missed_tick_time =
+      time_source_->SetActive(needs_begin_frames);
+  if (!missed_tick_time.is_null()) {
+    CallOnBeginFrame(
+        CreateBeginFrameArgs(missed_tick_time, BeginFrameArgs::MISSED));
+  }
+}
+
+bool SyntheticBeginFrameSource::NeedsBeginFrames() const {
+  return time_source_->Active();
+}
+
+// Tracing support
+void SyntheticBeginFrameSource::AsValueInto(
+    base::debug::TracedValue* dict) const {
+  dict->SetString("type", "SyntheticBeginFrameSource");
+  BeginFrameSourceMixIn::AsValueInto(dict);
+
+  dict->BeginDictionary("time_source");
+  time_source_->AsValueInto(dict);
+  dict->EndDictionary();
+}
+
+// BeginFrameSourceMultiplexer -------------------------------------------
+scoped_ptr<BeginFrameSourceMultiplexer> BeginFrameSourceMultiplexer::Create() {
+  return make_scoped_ptr(new BeginFrameSourceMultiplexer());
+}
+
+BeginFrameSourceMultiplexer::BeginFrameSourceMultiplexer()
+    : BeginFrameSourceMixIn(),
+      minimum_interval_(base::TimeDelta()),
+      active_source_(NULL),
+      source_list_() {
+}
+
+BeginFrameSourceMultiplexer::BeginFrameSourceMultiplexer(
+    base::TimeDelta minimum_interval)
+    : BeginFrameSourceMixIn(),
+      minimum_interval_(minimum_interval),
+      active_source_(NULL),
+      source_list_() {
+}
+
+BeginFrameSourceMultiplexer::~BeginFrameSourceMultiplexer() {
+}
+
+void BeginFrameSourceMultiplexer::SetMinimumInterval(
+    base::TimeDelta new_minimum_interval) {
+  DEBUG_FRAMES("BeginFrameSourceMultiplexer::SetMinimumInterval",
+               "current minimum (us)",
+               minimum_interval_.InMicroseconds(),
+               "new minimum (us)",
+               new_minimum_interval.InMicroseconds());
+  DCHECK_GE(new_minimum_interval.ToInternalValue(), 0);
+  minimum_interval_ = new_minimum_interval;
+}
+
+void BeginFrameSourceMultiplexer::AddSource(BeginFrameSource* new_source) {
+  DEBUG_FRAMES("BeginFrameSourceMultiplexer::AddSource",
+               "current active",
+               active_source_,
+               "source to remove",
+               new_source);
+  DCHECK(new_source);
+  DCHECK(!HasSource(new_source));
+
+  source_list_.insert(new_source);
+
+  // If there is no active source, set the new one as the active one.
+  if (!active_source_)
+    SetActiveSource(new_source);
+}
+
+void BeginFrameSourceMultiplexer::RemoveSource(
+    BeginFrameSource* existing_source) {
+  DEBUG_FRAMES("BeginFrameSourceMultiplexer::RemoveSource",
+               "current active",
+               active_source_,
+               "source to remove",
+               existing_source);
+  DCHECK(existing_source);
+  DCHECK(HasSource(existing_source));
+  DCHECK_NE(existing_source, active_source_);
+  source_list_.erase(existing_source);
+}
+
+void BeginFrameSourceMultiplexer::SetActiveSource(
+    BeginFrameSource* new_source) {
+  DEBUG_FRAMES("BeginFrameSourceMultiplexer::SetActiveSource",
+               "current active",
+               active_source_,
+               "to become active",
+               new_source);
+
+  DCHECK(HasSource(new_source) || new_source == NULL);
+
+  bool needs_begin_frames = NeedsBeginFrames();
+  if (active_source_) {
+    if (needs_begin_frames)
+      SetNeedsBeginFrames(false);
+
+    // Technically we shouldn't need to remove observation, but this prevents
+    // the case where SetNeedsBeginFrames message gets to the source after a
+    // message has already been sent.
+    active_source_->RemoveObserver(this);
+    active_source_ = NULL;
+  }
+  DCHECK(!active_source_);
+  active_source_ = new_source;
+
+  if (active_source_) {
+    active_source_->AddObserver(this);
+
+    if (needs_begin_frames) {
+      SetNeedsBeginFrames(true);
+    }
+  }
+}
+
+const BeginFrameSource* BeginFrameSourceMultiplexer::ActiveSource() {
+  return active_source_;
+}
+
+// BeginFrameObserver support
+void BeginFrameSourceMultiplexer::OnBeginFrame(const BeginFrameArgs& args) {
+  if (!IsIncreasing(args)) {
+    DEBUG_FRAMES("BeginFrameSourceMultiplexer::OnBeginFrame",
+                 "action",
+                 "discarding",
+                 "new args",
+                 args.AsValue());
+    return;
+  }
+  DEBUG_FRAMES("BeginFrameSourceMultiplexer::OnBeginFrame",
+               "action",
+               "using",
+               "new args",
+               args.AsValue());
+  CallOnBeginFrame(args);
+}
+
+const BeginFrameArgs BeginFrameSourceMultiplexer::LastUsedBeginFrameArgs()
+    const {
+  if (observer_)
+    return observer_->LastUsedBeginFrameArgs();
+  else
+    return BeginFrameArgs();
+}
+
+// BeginFrameSource support
+bool BeginFrameSourceMultiplexer::NeedsBeginFrames() const {
+  if (active_source_) {
+    return active_source_->NeedsBeginFrames();
+  } else {
+    return false;
+  }
+}
+
+void BeginFrameSourceMultiplexer::SetNeedsBeginFrames(bool needs_begin_frames) {
+  DEBUG_FRAMES("BeginFrameSourceMultiplexer::SetNeedsBeginFrames",
+               "active_source",
+               active_source_,
+               "needs_begin_frames",
+               needs_begin_frames);
+  if (active_source_) {
+    active_source_->SetNeedsBeginFrames(needs_begin_frames);
+  } else {
+    DCHECK(!needs_begin_frames);
+  }
+}
+
+void BeginFrameSourceMultiplexer::DidFinishFrame(size_t remaining_frames) {
+  DEBUG_FRAMES("BeginFrameSourceMultiplexer::DidFinishFrame",
+               "active_source",
+               active_source_,
+               "remaining_frames",
+               remaining_frames);
+  if (active_source_) {
+    active_source_->DidFinishFrame(remaining_frames);
+  }
+}
+
+// Tracing support
+void BeginFrameSourceMultiplexer::AsValueInto(
+    base::debug::TracedValue* dict) const {
+  dict->SetString("type", "BeginFrameSourceMultiplexer");
+
+  dict->SetInteger("minimum_interval_us", minimum_interval_.InMicroseconds());
+  if (observer_) {
+    dict->BeginDictionary("last_begin_frame_args");
+    observer_->LastUsedBeginFrameArgs().AsValueInto(dict);
+    dict->EndDictionary();
+  }
+
+  if (active_source_) {
+    dict->BeginDictionary("active_source");
+    active_source_->AsValueInto(dict);
+    dict->EndDictionary();
+  } else {
+    dict->SetString("active_source", "NULL");
+  }
+
+  for (std::set<BeginFrameSource*>::const_iterator it = source_list_.begin();
+       it != source_list_.end();
+       ++it) {
+    dict->BeginDictionary(
+        base::SizeTToString(std::distance(source_list_.begin(), it)).c_str());
+    (*it)->AsValueInto(dict);
+    dict->EndDictionary();
+  }
+}
+
+// protected methods
+bool BeginFrameSourceMultiplexer::HasSource(BeginFrameSource* source) {
+  return (source_list_.find(source) != source_list_.end());
+}
+
+bool BeginFrameSourceMultiplexer::IsIncreasing(const BeginFrameArgs& args) {
+  DCHECK(args.IsValid());
+  if (!observer_)
+    return false;
+
+  // If the last begin frame is invalid, then any new begin frame is valid.
+  if (!observer_->LastUsedBeginFrameArgs().IsValid())
+    return true;
+
+  // Only allow new args have a *strictly bigger* frame_time value and statisfy
+  // minimum interval requirement.
+  return (args.frame_time >=
+          observer_->LastUsedBeginFrameArgs().frame_time + minimum_interval_);
+}
+
+}  // namespace cc