Use the skmultipicture to perform GPU rasterization

cc/resources/gpu_raster_worker_pool.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/resources/gpu_raster_worker_pool.h"
 
 #include <algorithm>
 
 #include "base/debug/trace_event.h"
 #include "cc/output/context_provider.h"
 #include "cc/resources/raster_buffer.h"
 #include "cc/resources/resource.h"
 #include "cc/resources/resource_provider.h"
 #include "cc/resources/scoped_gpu_raster.h"
 #include "gpu/command_buffer/client/gles2_interface.h"
+#include "third_party/skia/include/core/SkMultiPictureDraw.h"
+#include "third_party/skia/include/core/SkPictureRecorder.h"
 #include "third_party/skia/include/core/SkSurface.h"
 #include "third_party/skia/include/gpu/GrContext.h"
 #include "third_party/skia/include/utils/SkNullCanvas.h"
 
 namespace cc {
 namespace {
 
 class RasterBufferImpl : public RasterBuffer {
  public:
   RasterBufferImpl(ResourceProvider* resource_provider,
-                   const Resource* resource)
+                   const Resource* resource,
+                   SkMultiPictureDraw* multi_picture_draw)
       : resource_provider_(resource_provider),
         resource_(resource),
-        surface_(resource_provider->LockForWriteToSkSurface(resource->id())) {}
+        surface_(resource_provider->LockForWriteToSkSurface(resource->id())),
+        multi_picture_draw_(multi_picture_draw) {}
   virtual ~RasterBufferImpl() {
     resource_provider_->UnlockForWriteToSkSurface(resource_->id());
   }
 
   // Overridden from RasterBuffer:
   virtual skia::RefPtr<SkCanvas> AcquireSkCanvas() OVERRIDE {
-    skia::RefPtr<SkCanvas> canvas = surface_
-                                        ? skia::SharePtr(surface_->getCanvas())
-                                        : skia::AdoptRef(SkCreateNullCanvas());
+    skia::RefPtr<SkCanvas> canvas = skia::SharePtr(recorder_.beginRecording(
+        resource_->size().width(), resource_->size().height()));
 
     // Balanced with restore() call in ReleaseSkCanvas. save()/restore() calls
     // are needed to ensure that canvas returns to its previous state after use.
     canvas->save();

[reveman, 2014/09/22 21:29:05]

do we still need this save/restore pair?

[hendrikw, 2014/09/22 21:48:39]

It is probably still required, but should be moved to wrap around the canvas
created below, since that's the canvas we need to keep in a good state.

I'll make the change.

[reveman, 2014/09/22 22:41:08]

Acknowledged.

     return canvas;
   }
   virtual void ReleaseSkCanvas(const skia::RefPtr<SkCanvas>& canvas) OVERRIDE {
     // Balanced with save() call in AcquireSkCanvas.
     canvas->restore();
+
+    // Add the canvas and recorded picture to |multi_picture_draw_|.
+    skia::RefPtr<SkCanvas> real_canvas =
+        surface_ ? skia::SharePtr(surface_->getCanvas())
+                 : skia::AdoptRef(SkCreateNullCanvas());

[reveman, 2014/09/22 21:29:05]

it seems a bit silly to add a null canvas. would it make more sense to not add
the picture when surface_ is NULL?

[hendrikw, 2014/09/22 21:48:39]

If we want status quo, I should probably allocate the surface canvas in the
AquireSkCanvas, and if the surface is missing, do not bother creating the
recorder canvas, and return the null canvas there.

That means I would need to keep a pointer to both canvases, which isn't a big
deal.

+    skia::RefPtr<SkPicture> picture = skia::AdoptRef(recorder_.endRecording());
+    multi_picture_draw_->add(real_canvas.get(), picture.get());
   }
 
  private:
   ResourceProvider* resource_provider_;
   const Resource* resource_;
   SkSurface* surface_;
+  SkMultiPictureDraw* multi_picture_draw_;
+  SkPictureRecorder recorder_;
 
   DISALLOW_COPY_AND_ASSIGN(RasterBufferImpl);
 };
 
 }  // namespace
 
 // static
 scoped_ptr<RasterWorkerPool> GpuRasterWorkerPool::Create(
     base::SequencedTaskRunner* task_runner,
     ContextProvider* context_provider,
@@ skipping 117 matching lines @@
   completed_tasks_.clear();
 }
 
 scoped_ptr<RasterBuffer> GpuRasterWorkerPool::AcquireBufferForRaster(
     const Resource* resource) {
   // RasterBuffer implementation depends on a SkSurface having been acquired for
   // the resource.
   resource_provider_->AcquireSkSurface(resource->id());
 
   return make_scoped_ptr<RasterBuffer>(
-      new RasterBufferImpl(resource_provider_, resource));
+      new RasterBufferImpl(resource_provider_, resource, &multi_picture_draw_));
 }
 
 void GpuRasterWorkerPool::ReleaseBufferForRaster(
     scoped_ptr<RasterBuffer> buffer) {
   // Nothing to do here. RasterBufferImpl destructor cleans up after itself.
 }
 
 void GpuRasterWorkerPool::OnRasterFinished(TaskSet task_set) {
   TRACE_EVENT1(
       "cc", "GpuRasterWorkerPool::OnRasterFinished", "task_set", task_set);
@@ skipping 15 matching lines @@
 }
 
 void GpuRasterWorkerPool::RunTasksOnOriginThread() {
   TRACE_EVENT0("cc", "GpuRasterWorkerPool::RunTasksOnOriginThread");
 
   DCHECK(run_tasks_on_origin_thread_pending_);
   run_tasks_on_origin_thread_pending_ = false;
 
   ScopedGpuRaster gpu_raster(context_provider_);
   task_graph_runner_->RunUntilIdle();
+  multi_picture_draw_.draw();

[reveman, 2014/09/22 21:29:05]

Does calling draw() also clear the SkMultiPictureDraw? Maybe do that explicitly
instead or add a comment..

[hendrikw, 2014/09/22 21:48:39]

Yes, it clears.  I'll add a comment.

 }
 
 }  // namespace cc