Refactoring the way begin frame sources inside scheduler work.

cc/scheduler/frame_source.cc

+// 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/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(...)                                              \
+  TRACE_EVENT2(TRACE_DISABLED_BY_DEFAULT("cc.debug.scheduler.frames"), \
+               __VA_ARGS__);
+#endif
+
+namespace cc {
+
+// BeginFrameObserverImpl ------------------------------------------------
+const BeginFrameArgs BeginFrameObserverImpl::LastBeginFrameArgs() const {
+  return last_begin_frame_args_;
+}
+void BeginFrameObserverImpl::OnBeginFrame(const BeginFrameArgs& args) {
+  DEBUG_FRAMES("BeginFrameObserverImpl::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);
+  DCHECK(args.frame_time >= last_begin_frame_args_.frame_time);

[simonhong, 2014/09/23 04:39:09]

Is it possible to equal?

[mithro-old, 2014/09/23 12:43:54]

Currently this occurs in tests (and I don't want to fix that issue in this CL
too). When they are eventually fixed to create frame times which increase, then
we can move to the more strict greater than.

+  if (OnBeginFrameImpl(args))
+    last_begin_frame_args_ = args;
+}
+
+void BeginFrameObserverImpl::OnMissedBeginFrame(const BeginFrameArgs& args) {
+  DEBUG_FRAMES("BeginFrameObserverImpl::OnMissedBeginFrame",
+               "last args",
+               last_begin_frame_args_.AsValue(),
+               "new args",
+               args.AsValue());
+  OnBeginFrame(args);
+}
+
+void BeginFrameObserverImpl::AsValueInto(base::debug::TracedValue* dict) const {
+  dict->BeginDictionary("last_begin_frame_args_");
+  last_begin_frame_args_.AsValueInto(dict);
+  dict->EndDictionary();
+}
+
+// BeginFrameSource ------------------------------------------------------
+BeginFrameSource::BeginFrameSource()
+    : observer_(NULL), inside_as_value_into_(false) {

[simonhong, 2014/09/23 04:39:09]

I think below DCHECKs can be removed if you don't suspect
compiler ;)

+  DCHECK(!observer_);
+  DCHECK_EQ(inside_as_value_into_, false);
+}
+
+void BeginFrameSource::AddObserver(BeginFrameObserver* obs) {
+  DEBUG_FRAMES("BeginFrameSource::AddObserver",
+               "current observer",
+               observer_,
+               "to add observer",
+               obs);
+  DCHECK(!observer_);
+  observer_ = obs;
+}
+
+void BeginFrameSource::RemoveObserver(BeginFrameObserver* obs) {
+  DEBUG_FRAMES("BeginFrameSource::RemoveObserver",
+               "current observer",
+               observer_,
+               "to remove observer",
+               obs);
+  DCHECK_EQ(observer_, obs);
+  observer_ = NULL;
+}
+
+void BeginFrameSource::CallOnBeginFrame(const BeginFrameArgs& args) {
+  DEBUG_FRAMES("BeginFrameSource::CallOnBeginFrame",
+               "current observer",
+               observer_,
+               "args",
+               args.AsValue());
+  if (observer_) {
+    observer_->OnBeginFrame(args);
+  }
+}
+
+void BeginFrameSource::CallOnMissedBeginFrame(const BeginFrameArgs& args) {
+  DEBUG_FRAMES("BeginFrameSource::CallOnMissedBeginFrame",
+               "current observer",
+               observer_,
+               "args",
+               args.AsValue());
+  if (observer_) {
+    observer_->OnMissedBeginFrame(args);
+  }
+}
+
+// Tracing support
+void BeginFrameSource::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");
+  }
+}
+
+// BackToBackBeginFrameSource --------------------------------------------
+scoped_ptr<BackToBackBeginFrameSource> BackToBackBeginFrameSource::Create(
+    base::SingleThreadTaskRunner* task_runner) {
+  return make_scoped_ptr(new BackToBackBeginFrameSource(task_runner));
+}
+
+BackToBackBeginFrameSource::BackToBackBeginFrameSource(
+    base::SingleThreadTaskRunner* task_runner)
+    : BeginFrameSource(),
+      weak_factory_(this),
+      task_runner_(task_runner),
+      needs_begin_frames_(false),
+      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::ScheduleBeginFrame() {
+  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);
+}
+
+// BackToBackBeginFrameSource --------------------------------------------
+bool BackToBackBeginFrameSource::NeedsBeginFrames() const {
+  return needs_begin_frames_;
+}
+
+void BackToBackBeginFrameSource::SetNeedsBeginFrames(bool needs_begin_frames) {
+  needs_begin_frames_ = needs_begin_frames;
+  ScheduleBeginFrame();
+}
+
+void BackToBackBeginFrameSource::DidFinishFrame(size_t remaining_frames) {
+  if (remaining_frames == 0) {
+    ScheduleBeginFrame();
+  }
+}
+
+// Tracing
+void BackToBackBeginFrameSource::AsValueInto(
+    base::debug::TracedValue* dict) const {
+  dict->SetString("type", "BackToBackBeginFrameSource");
+  BeginFrameSource::AsValueInto(dict);
+  dict->SetBoolean("send_begin_frame_posted_", send_begin_frame_posted_);
+  dict->SetBoolean("needs_begin_frames", needs_begin_frames_);
+}
+
+// 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)
+    : BeginFrameSource(), 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);
+}
+
+void SyntheticBeginFrameSource::SendBeginFrameFromTick(
+    base::TimeTicks frame_time) {
+  base::TimeTicks deadline = time_source_->NextTickTime();
+  CallOnBeginFrame(
+      BeginFrameArgs::Create(frame_time, deadline, time_source_->Interval()));
+}
+
+// TimeSourceClient
+void SyntheticBeginFrameSource::OnTimerTick() {
+  SendBeginFrameFromTick(time_source_->LastTickTime());
+}
+
+// BeginFrameSource
+void SyntheticBeginFrameSource::SetNeedsBeginFrames(bool needs_begin_frames) {
+  if (needs_begin_frames == NeedsBeginFrames())
+    return;
+
+  base::TimeTicks missed_tick_time =
+      time_source_->SetActive(needs_begin_frames);
+  if (!missed_tick_time.is_null()) {
+    SendBeginFrameFromTick(missed_tick_time);
+  }
+}
+
+bool SyntheticBeginFrameSource::NeedsBeginFrames() const {
+  return time_source_->Active();
+}
+
+// Tracing
+void SyntheticBeginFrameSource::AsValueInto(
+    base::debug::TracedValue* dict) const {
+  dict->SetString("type", "SyntheticBeginFrameSource");
+  BeginFrameSource::AsValueInto(dict);
+
+  dict->BeginDictionary("last_frame_args");
+  time_source_->AsValueInto(dict);
+  dict->EndDictionary();
+}
+
+// BeginFrameSourceMultiplexer -------------------------------------------
+scoped_ptr<BeginFrameSourceMultiplexer> BeginFrameSourceMultiplexer::Create() {
+  return make_scoped_ptr(new BeginFrameSourceMultiplexer());
+}
+
+BeginFrameSourceMultiplexer::BeginFrameSourceMultiplexer()
+    : BeginFrameSource(),
+      minimum_interval_(base::TimeDelta()),
+      active_source_(NULL),
+      source_list_() {
+}
+
+BeginFrameSourceMultiplexer::BeginFrameSourceMultiplexer(
+    base::TimeDelta minimum_interval)
+    : BeginFrameSource(),
+      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
+void BeginFrameSourceMultiplexer::OnBeginFrame(const BeginFrameArgs& args) {
+  if (!IsIncreasing(args)) {
+    DEBUG_FRAMES("BeginFrameSourceMultiplexer::OnBeginFrame",
+                 "action",
+                 "discarding",
+                 "new args",
+                 args.AsValue());
+    return;
+  } else {
+    DEBUG_FRAMES("BeginFrameSourceMultiplexer::OnBeginFrame",
+                 "action",
+                 "using",
+                 "new args",
+                 args.AsValue());
+  }
+  CallOnBeginFrame(args);
+}
+
+void BeginFrameSourceMultiplexer::OnMissedBeginFrame(
+    const BeginFrameArgs& args) {
+  if (!IsIncreasing(args)) {
+    DEBUG_FRAMES("BeginFrameSourceMultiplexer::OnMissedBeginFrame",
+                 "action",
+                 "discarding",
+                 "new args",
+                 args.AsValue());
+    return;
+  } else {
+    DEBUG_FRAMES("BeginFrameSourceMultiplexer::OnMissedBeginFrame",
+                 "action",
+                 "using",
+                 "new args",
+                 args.AsValue());
+  }
+  CallOnMissedBeginFrame(args);
+}
+
+const BeginFrameArgs BeginFrameSourceMultiplexer::LastBeginFrameArgs() const {
+  if (observer_)
+    return observer_->LastBeginFrameArgs();
+  else
+    return BeginFrameArgs();
+}
+
+// BeginFrameSource
+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
+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_->LastBeginFrameArgs().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, than any new begin frame is valid.
+  if (!observer_->LastBeginFrameArgs().IsValid())
+    return true;
+
+  // Only allow new args have a *strictly bigger* frame_time value and statisfy
+  // minimum interval requirement.
+  return (  // args.frame_time > observer_->LastBeginFrameArgs().frame_time &&
+      args.frame_time >=
+      observer_->LastBeginFrameArgs().frame_time + minimum_interval_);
+}
+
+}  // namespace cc