cc: Emulate BeginFrame in OutputSurfaces that don't support it natively

cc/scheduler/scheduler.cc

Index: cc/scheduler/scheduler.cc
diff --git a/cc/scheduler/scheduler.cc b/cc/scheduler/scheduler.cc
index 737ffc1bb1222b2af5fec3d72e7a468abd4fa2ad..cf3fad51c7cc264d95e1692c7ab726f57d4d815f 100644
--- a/cc/scheduler/scheduler.cc
+++ b/cc/scheduler/scheduler.cc
@@ -2,7 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "cc/base/thread.h"
 #include "cc/scheduler/scheduler.h"
+#include "cc/trees/proxy.h"
 
 #include "base/auto_reset.h"
 #include "base/debug/trace_event.h"
@@ -11,19 +13,26 @@
 namespace cc {
 
 Scheduler::Scheduler(SchedulerClient* client,
-                     scoped_ptr<FrameRateController> frame_rate_controller,
-                     const SchedulerSettings& scheduler_settings)
+                     const SchedulerSettings& scheduler_settings,
+                     Thread *thread)
     : settings_(scheduler_settings),
       client_(client),
-      frame_rate_controller_(frame_rate_controller.Pass()),
+      weak_factory_(this),
+      thread_(thread),
+      last_set_needs_begin_frame_(false),
+      pending_begin_frames_(0),
+      last_begin_frame_time_(base::TimeTicks::Now()),
+      //TODO(brianderson): Pass with BeginFrame in the near future.
+      interval_(base::TimeDelta::FromMicroseconds(16666)),
       state_machine_(scheduler_settings),
       inside_process_scheduled_actions_(false) {
   DCHECK(client_);
-  frame_rate_controller_->SetClient(this);
   DCHECK(!state_machine_.BeginFrameNeededByImplThread());
 }
 
-Scheduler::~Scheduler() { frame_rate_controller_->SetActive(false); }
+Scheduler::~Scheduler() {
+  client_->SetNeedsBeginFrameOnImplThread(false);
+}
 
 void Scheduler::SetCanStart() {
   state_machine_.SetCanStart();
@@ -88,25 +97,8 @@ void Scheduler::BeginFrameAbortedByMainThread() {
   ProcessScheduledActions();
 }
 
-void Scheduler::SetMaxFramesPending(int max_frames_pending) {
-  frame_rate_controller_->SetMaxFramesPending(max_frames_pending);
-}
-
-int Scheduler::MaxFramesPending() const {
-  return frame_rate_controller_->MaxFramesPending();
-}
-
-int Scheduler::NumFramesPendingForTesting() const {
-  return frame_rate_controller_->NumFramesPendingForTesting();
-}
-
-void Scheduler::SetSwapBuffersCompleteSupported(bool supported) {
-  frame_rate_controller_->SetSwapBuffersCompleteSupported(supported);
-}
-
-void Scheduler::DidSwapBuffersComplete() {
-  TRACE_EVENT0("cc", "Scheduler::DidSwapBuffersComplete");
-  frame_rate_controller_->DidSwapBuffersComplete();
+void Scheduler::DidSwapBuffers() {
+  pending_begin_frames_--;
 }
 
 void Scheduler::DidLoseOutputSurface() {
@@ -117,31 +109,73 @@ void Scheduler::DidLoseOutputSurface() {
 
 void Scheduler::DidCreateAndInitializeOutputSurface() {
   TRACE_EVENT0("cc", "Scheduler::DidCreateAndInitializeOutputSurface");
-  frame_rate_controller_->DidAbortAllPendingFrames();
   state_machine_.DidCreateAndInitializeOutputSurface();
+  last_set_needs_begin_frame_ = false;
   ProcessScheduledActions();
 }
 
-void Scheduler::SetTimebaseAndInterval(base::TimeTicks timebase,
-                                       base::TimeDelta interval) {
-  frame_rate_controller_->SetTimebaseAndInterval(timebase, interval);
-}
-
 base::TimeTicks Scheduler::AnticipatedDrawTime() {
-  return frame_rate_controller_->NextTickTime();
+  TRACE_EVENT0("cc", "Scheduler::AnticipatedDrawTime");
+  base::TimeTicks now = base::TimeTicks::Now();
+  base::TimeTicks draw_time = last_begin_frame_time_;
+  while (draw_time < now) {
+    draw_time += interval_;
+  }

[brianderson, 2013/06/01 04:30:29]

This is way hacky, but will be hard to improve until we implement a message to
the BeginFrame provider that we need another BeginFrame without having drawn.

Without this, the texture uploader stops uploading because the
AnticipatedDrawTime becomes stale.

[Sami, 2013/06/03 17:30:33]

Is this the only instance where we're requesting a BeginFrame without actually
wanting to render? If so, maybe we should consider using some other mechanism to
drive texture uploads so that BeginFrame can be used for one specific purpose.

[brianderson, 2013/06/03 18:51:40]

Later we'll want to request a new BeginFrame anytime the Main thread runs long
so that the Impl thread can get an updated deadline.

Thinking about this function some more though, I think I can implement it in a
less hacky way by updating the draw time in BeginFrameRetry and setting the draw
time to 0 when there isn't a pending draw.

+
+  return draw_time;
 }
 
 base::TimeTicks Scheduler::LastBeginFrameOnImplThreadTime() {
-  return frame_rate_controller_->LastTickTime();
+  return last_begin_frame_time_;
+}
+
+void Scheduler::SetNeedsBeginFrameIfNeeded() {
+  // Determine if we need BeginFrame notifications.
+  // If we do, always request the BeginFrame immediately.
+  // If not, only disable on the next BeginFrame to avoid unnecessary toggles.
+  // The synchronous renderer compositor requires immediate disables though.
+  bool needs_begin_frame = state_machine_.BeginFrameNeededByImplThread();
+  if ((needs_begin_frame ||
+       state_machine_.inside_begin_frame() ||
+       settings_.using_synchronous_renderer_compositor) &&
+      (needs_begin_frame != last_set_needs_begin_frame_)) {

[brianderson, 2013/06/01 04:30:29]

I'll need someone working on the synchronous compositor to verify I transfered
the logic over correctly here.

+    client_->SetNeedsBeginFrameOnImplThread(needs_begin_frame);
+    last_set_needs_begin_frame_ = needs_begin_frame;
+  }
+
+  if (state_machine_.inside_begin_frame()) {
+    if (pending_begin_frames_ && !needs_begin_frame) {
+      // Balance out the unhandled BeginFrames with Swaps.
+      // TODO(brianderson): Replace this duplicate swap with a "SwapSkip".

[brianderson, 2013/06/01 04:30:29]

I should move this into a function; it's duplicated code from
ProcessScheduledActions.

+      ScheduledActionDrawAndSwapResult result =
+          client_->ScheduledActionDrawAndSwapForced();
+      if (result.did_swap)
+        DidSwapBuffers();
+    }
+    if (pending_begin_frames_) {
+      // Self tick to retry a failed BeginFrame
+      // TODO(brianderson): Implement smarter polling when deadlines are added.
+      thread_->PostDelayedTask(
+          base::Bind(&Scheduler::BeginFrameRetry, weak_factory_.GetWeakPtr()),
+          interval_);
+    }
+  }
+}
+
+void Scheduler::BeginFrame(base::TimeTicks frame_time) {
+  TRACE_EVENT0("cc", "Scheduler::BeginFrame");
+  pending_begin_frames_++;
+  last_begin_frame_time_ = frame_time;
+  state_machine_.DidEnterBeginFrame();
+  ProcessScheduledActions();
+  state_machine_.DidLeaveBeginFrame();
 }
 
-void Scheduler::BeginFrame(bool throttled) {
-  TRACE_EVENT1("cc", "Scheduler::BeginFrame", "throttled", throttled);
-  if (!throttled)
-    state_machine_.DidEnterBeginFrame();
+void Scheduler::BeginFrameRetry() {
+  TRACE_EVENT0("cc", "Scheduler::BeginFrameRetry");
+  state_machine_.DidEnterBeginFrame();
   ProcessScheduledActions();
-  if (!throttled)
-    state_machine_.DidLeaveBeginFrame();
+  state_machine_.DidLeaveBeginFrame();
 }
 
 void Scheduler::ProcessScheduledActions() {
@@ -155,8 +189,10 @@ void Scheduler::ProcessScheduledActions() {
   SchedulerStateMachine::Action action = state_machine_.NextAction();
   while (action != SchedulerStateMachine::ACTION_NONE) {
     state_machine_.UpdateState(action);
-    TRACE_EVENT1(
-        "cc", "Scheduler::ProcessScheduledActions()", "action", action);
+    TRACE_EVENT2(
+        "cc", "Scheduler::ProcessScheduledActions()",
+        "action", action,
+        "state", state_machine_.ToString());
 
     switch (action) {
       case SchedulerStateMachine::ACTION_NONE:
@@ -178,14 +214,14 @@ void Scheduler::ProcessScheduledActions() {
             client_->ScheduledActionDrawAndSwapIfPossible();
         state_machine_.DidDrawIfPossibleCompleted(result.did_draw);
         if (result.did_swap)
-          frame_rate_controller_->DidSwapBuffers();
+          DidSwapBuffers();
         break;
       }
       case SchedulerStateMachine::ACTION_DRAW_FORCED: {
         ScheduledActionDrawAndSwapResult result =
             client_->ScheduledActionDrawAndSwapForced();
         if (result.did_swap)
-          frame_rate_controller_->DidSwapBuffers();
+          DidSwapBuffers();
         break;
       }
       case SchedulerStateMachine::ACTION_BEGIN_OUTPUT_SURFACE_CREATION:
@@ -198,10 +234,8 @@ void Scheduler::ProcessScheduledActions() {
     action = state_machine_.NextAction();
   }
 
-  // Activate or deactivate the frame rate controller.
-  frame_rate_controller_->SetActive(
-      state_machine_.BeginFrameNeededByImplThread());
-  client_->DidAnticipatedDrawTimeChange(frame_rate_controller_->NextTickTime());
+  SetNeedsBeginFrameIfNeeded();
+  client_->DidAnticipatedDrawTimeChange(AnticipatedDrawTime());
 }
 
 bool Scheduler::WillDrawIfNeeded() const {