cc: Making BeginFrameSources support multiple BeginFrameObservers.

cc/scheduler/begin_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/begin_frame_source.h"
 
 #include "base/auto_reset.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 15 matching lines @@
                arg2_val);
 #endif
 
 namespace cc {
 
 // BeginFrameObserverMixIn -----------------------------------------------
 BeginFrameObserverMixIn::BeginFrameObserverMixIn()
     : last_begin_frame_args_(), dropped_begin_frame_args_(0) {
 }
 
-const BeginFrameArgs BeginFrameObserverMixIn::LastUsedBeginFrameArgs() const {
+const BeginFrameArgs BeginFrameObserverMixIn::LastUsedBeginFrameArgs() {
   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::trace_event::TracedValue* dict) const {
+    base::trace_event::TracedValue* dict) {
   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),
+    : observer_list_(),
       needs_begin_frames_(false),
       inside_as_value_into_(false) {
-  DCHECK(!observer_);
   DCHECK_EQ(inside_as_value_into_, false);
 }
 
+BeginFrameSourceMixIn::~BeginFrameSourceMixIn() {
+}
+
 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) {
     needs_begin_frames_ = needs_begin_frames;
     OnNeedsBeginFramesChange(needs_begin_frames);
   }
 }
 
 void BeginFrameSourceMixIn::AddObserver(BeginFrameObserver* obs) {
-  DEBUG_FRAMES("BeginFrameSourceMixIn::AddObserver",
-               "current observer",
-               observer_,
-               "to add observer",
-               obs);
-  DCHECK(!observer_);
-  observer_ = obs;
+  DEBUG_FRAMES("BeginFrameSourceMixIn::AddObserver", "has observers?",
+               (observer_list_).might_have_observers(), "to add observer", obs);
+  DCHECK(obs);
+  DCHECK(!observer_list_.HasObserver(obs));
+  observer_list_.AddObserver(obs);
 }
 
 void BeginFrameSourceMixIn::RemoveObserver(BeginFrameObserver* obs) {
-  DEBUG_FRAMES("BeginFrameSourceMixIn::RemoveObserver",
-               "current observer",
-               observer_,
-               "to remove observer",
+  DEBUG_FRAMES("BeginFrameSourceMixIn::RemoveObserver", "has observers?",
+               (observer_list_).might_have_observers(), "to remove observer",
                obs);
-  DCHECK_EQ(observer_, obs);
-  observer_ = NULL;
+  DCHECK(obs);
+  DCHECK(observer_list_.HasObserver(obs));
+  observer_list_.RemoveObserver(obs);
 }
 
 void BeginFrameSourceMixIn::CallOnBeginFrame(const BeginFrameArgs& args) {
-  DEBUG_FRAMES("BeginFrameSourceMixIn::CallOnBeginFrame",
-               "current observer",
-               observer_,
-               "args",
-               args.AsValue());
-  if (observer_) {
-    return observer_->OnBeginFrame(args);
-  }
+  DEBUG_FRAMES("BeginFrameSourceMixIn::CallOnBeginFrame", "has observers?",
+               observer_list_.might_have_observers(), "args", args.AsValue());
+  FOR_EACH_OBSERVER(BeginFrameObserver, observer_list_, OnBeginFrame(args));
 }
 
 // Tracing support
-void BeginFrameSourceMixIn::AsValueInto(
-    base::trace_event::TracedValue* dict) const {
+void BeginFrameSourceMixIn::AsValueInto(base::trace_event::TracedValue* dict) {
   // 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;
   }
+  base::AutoReset<bool> prevent_loops(const_cast<bool*>(&inside_as_value_into_),
+                                      true);
 
-  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());
+  if (observer_list_.might_have_observers()) {
+    ObserverList<BeginFrameObserver>::Iterator it(&observer_list_);
+    BeginFrameObserver* obs;
+    dict->BeginArray("observers");
+    while ((obs = it.GetNext()) != NULL) {
+      dict->BeginDictionary();
+      obs->AsValueInto(dict);
+      dict->EndDictionary();
+    }
+    dict->EndArray();
   }
-  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)
@@ skipping 43 matching lines @@
 // BeginFrameSource support
 
 void BackToBackBeginFrameSource::DidFinishFrame(size_t remaining_frames) {
   if (remaining_frames == 0) {
     OnNeedsBeginFramesChange(NeedsBeginFrames());
   }
 }
 
 // Tracing support
 void BackToBackBeginFrameSource::AsValueInto(
-    base::trace_event::TracedValue* dict) const {
+    base::trace_event::TracedValue* dict) {

[danakj, 2015/03/25 18:12:55]

What's with all the const changes? AsValueInto can't be related to using an
ObserverList?

[mithro-old, 2015/03/26 00:54:49]

The AsValueInto loops over each of the observers. Iterating over an ObserverList
is non const operation.

   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) {
@@ skipping 47 matching lines @@
   base::TimeTicks missed_tick_time =
       time_source_->SetActive(needs_begin_frames);
   if (!missed_tick_time.is_null()) {
     CallOnBeginFrame(
         CreateBeginFrameArgs(missed_tick_time, BeginFrameArgs::MISSED));
   }
 }
 
 // Tracing support
 void SyntheticBeginFrameSource::AsValueInto(
-    base::trace_event::TracedValue* dict) const {
+    base::trace_event::TracedValue* dict) {
   dict->SetString("type", "SyntheticBeginFrameSource");
   BeginFrameSourceMixIn::AsValueInto(dict);
 
   dict->BeginDictionary("time_source");
   time_source_->AsValueInto(dict);
   dict->EndDictionary();
 }
 
 // BeginFrameSourceMultiplexer -------------------------------------------
 scoped_ptr<BeginFrameSourceMultiplexer> BeginFrameSourceMultiplexer::Create() {
@@ skipping 106 matching lines @@
     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();
+const BeginFrameArgs BeginFrameSourceMultiplexer::LastUsedBeginFrameArgs() {
+  BeginFrameArgs last;
+
+  if ((observer_list_).might_have_observers()) {
+    ObserverList<BeginFrameObserver>::Iterator it(&observer_list_);
+    BeginFrameObserver* obs;
+    while ((obs = it.GetNext()) != NULL) {
+      BeginFrameArgs obs_last = obs->LastUsedBeginFrameArgs();
+      if (obs_last.frame_time > last.frame_time)
+        last = obs_last;
+    }
+  }
+  return last;
 }
 
 // BeginFrameSource support
 void BeginFrameSourceMultiplexer::OnNeedsBeginFramesChange(
     bool needs_begin_frames) {
   DEBUG_FRAMES("BeginFrameSourceMultiplexer::OnNeedsBeginFramesChange",
                "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::trace_event::TracedValue* dict) const {
+    base::trace_event::TracedValue* dict) {
   dict->SetString("type", "BeginFrameSourceMultiplexer");
+  BeginFrameSourceMixIn::AsValueInto(dict);
 
   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");
   }
 
   dict->BeginArray("sources");
   for (std::set<BeginFrameSource*>::const_iterator it = source_list_.begin();
        it != source_list_.end();
        ++it) {
     dict->BeginDictionary();
     (*it)->AsValueInto(dict);
     dict->EndDictionary();
   }
   dict->EndArray();
 }
 
 // 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())
+  if (!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_);
+          LastUsedBeginFrameArgs().frame_time + minimum_interval_);
 }
 
 }  // namespace cc