Call OnSwapBuffersComplete at the end of each frame

content/browser/android/in_process/synchronous_compositor_output_surface.cc

 // Copyright 2013 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 "content/browser/android/in_process/synchronous_compositor_output_surface.h"
 
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/time.h"
 #include "cc/output/compositor_frame.h"
@@ skipping 44 matching lines @@
   SoftwareDevice(SynchronousCompositorOutputSurface* surface)
     : surface_(surface),
       null_device_(SkBitmap::kARGB_8888_Config, 1, 1),
       null_canvas_(&null_device_) {
   }
   virtual void Resize(gfx::Size size) OVERRIDE {
     // Intentional no-op: canvas size is controlled by the embedder.
   }
   virtual SkCanvas* BeginPaint(gfx::Rect damage_rect) OVERRIDE {
     DCHECK(surface_->current_sw_canvas_);
-    if (surface_->current_sw_canvas_)
-      return surface_->current_sw_canvas_;
-    return &null_canvas_;
+    if (!surface_->current_sw_canvas_) {
+      LOG(WARNING) << "BeginPaint with no canvas set";
+      return &null_canvas_;
+    }
+    LOG_IF(WARNING, surface_->did_swap_buffer_)
+        << "Mutliple calls to BeginPaint per frame";
+    return surface_->current_sw_canvas_;
   }
   virtual void EndPaint(cc::SoftwareFrameData* frame_data) OVERRIDE {
-    surface_->current_sw_canvas_ = NULL;
+    surface_->did_swap_buffer_ = true;
   }
   virtual void CopyToBitmap(gfx::Rect rect, SkBitmap* output) OVERRIDE {
     NOTIMPLEMENTED();
   }
   virtual void Scroll(gfx::Vector2d delta,
                       gfx::Rect clip_rect) OVERRIDE {
     NOTIMPLEMENTED();
   }
   virtual void ReclaimDIB(const TransportDIB::Id& id) OVERRIDE {
     NOTIMPLEMENTED();
@@ skipping 85 matching lines @@
     damage_area = gfx::ToEnclosedRect(gfx::SkRectToRectF(canvas_clip));
   } else {
     damage_area = gfx::Rect(kint16max, kint16max);
   }
 
   gfx::Transform transform;
   transform.matrix() = canvas->getTotalMatrix();  // Converts 3x3 matrix to 4x4.
 
   InvokeComposite(transform, damage_area);
 
-  bool finished_draw = current_sw_canvas_ == NULL;
   current_sw_canvas_ = NULL;
-  return finished_draw;
+  return did_swap_buffer_;
 }
 
 bool SynchronousCompositorOutputSurface::DemandDrawHw(
       gfx::Size view_size,
       const gfx::Transform& transform,
       gfx::Rect damage_area) {
   DCHECK(CalledOnValidThread());
   DCHECK(client_);
   DCHECK(context3d());
 
   // Force a GL state restore next time a GLContextVirtual is made current.
   // TODO(boliu): Move this to the end of this function after we have fixed
   // all cases of MakeCurrent calls outside of draws. Tracked in
   // crbug.com/239856.
   gfx::GLContext* current_context = gfx::GLContext::GetCurrent();
   if (current_context)
     current_context->ReleaseCurrent(NULL);
 
-  did_swap_buffer_ = false;
 
   InvokeComposite(transform, damage_area);
 
   return did_swap_buffer_;
 }
 
 void SynchronousCompositorOutputSurface::InvokeComposite(
     const gfx::Transform& transform,
     gfx::Rect damage_area) {
+  did_swap_buffer_ = false;
   // TODO(boliu): This assumes |transform| is identity and |damage_area| is the
   // whole view. Tracking bug to implement this: crbug.com/230463.
   client_->SetNeedsRedrawRect(damage_area);
   if (needs_begin_frame_)
     client_->BeginFrame(base::TimeTicks::Now());
+
+  if (did_swap_buffer_)
+    client_->OnSwapBuffersComplete();

[no sievers, 2013/06/05 21:08:05]

Is it even more straightforward to call this from SwapBuffers() (or maybe post a
task from there)?

[joth, 2013/06/05 21:26:40]

SwapBuffers() isn't called in the SW draw case.

 }
 
 // Not using base::NonThreadSafe as we want to enforce a more exacting threading
 // requirement: SynchronousCompositorOutputSurface() must only be used on the UI
 // thread.
 bool SynchronousCompositorOutputSurface::CalledOnValidThread() const {
   return BrowserThread::CurrentlyOn(BrowserThread::UI);
 }
 
 SynchronousCompositorOutputSurfaceDelegate*
 SynchronousCompositorOutputSurface::GetDelegate() {
   return SynchronousCompositorImpl::FromRoutingID(routing_id_);
 }
 
 }  // namespace content