Implemented software output device for Aura.

content/renderer/gpu/compositor_software_output_device.cc

Index: content/renderer/gpu/compositor_software_output_device.cc
diff --git a/content/renderer/gpu/compositor_software_output_device.cc b/content/renderer/gpu/compositor_software_output_device.cc
new file mode 100644
index 0000000000000000000000000000000000000000..0c521790c25f4a2b043d6bebc82ede57c15ef193
--- /dev/null
+++ b/content/renderer/gpu/compositor_software_output_device.cc
@@ -0,0 +1,143 @@
+// Copyright (c) 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/renderer/gpu/compositor_software_output_device.h"
+
+#include "base/logging.h"
+#include "cc/output/software_frame_data.h"
+#include "third_party/skia/include/core/SkCanvas.h"
+#include "third_party/skia/include/core/SkDevice.h"
+#include "third_party/skia/include/core/SkPixelRef.h"
+#include "ui/gfx/skia_util.h"
+
+namespace content {
+
+namespace {
+
+class CompareById {
+ public:
+  CompareById(const TransportDIB::Id& id)
+      : id_(id) {
+  }
+
+  bool operator()(const TransportDIB* dib) const {
+    return dib->id() == id_;
+  }
+
+ private:
+  TransportDIB::Id id_;
+};
+
+}  // namespace
+
+CompositorSoftwareOutputDevice::CompositorSoftwareOutputDevice()
+    : front_buffer_(0),
+      last_buffer_(-1),
+      num_free_buffers_(0),
+      sequence_num_(0) {
+  DetachFromThread();
+}
+
+CompositorSoftwareOutputDevice::~CompositorSoftwareOutputDevice() {
+  DCHECK(CalledOnValidThread());
+}
+
+TransportDIB* CompositorSoftwareOutputDevice::CreateDIB() {
+  const size_t size = 4 * viewport_size_.GetArea();
+  TransportDIB* dib = TransportDIB::Create(size, sequence_num_++);
+  CHECK(dib);
+  bool success = dib->Map();
+  CHECK(success);
+  return dib;
+}
+
+void CompositorSoftwareOutputDevice::Resize(gfx::Size viewport_size) {
+  DCHECK(CalledOnValidThread());
+
+  // Reset last_buffer_ so that we don't copy over old damage.
+  last_buffer_ = -1;
+
+  if (viewport_size_ == viewport_size)
+    return;
+  viewport_size_ = viewport_size;
+
+  // Reallocate dibs_.
+  dibs_.clear();

[piman, 2013/03/29 00:23:53]

From previous review: I still don't understand why it's safe. When you call Send
for the SwapCompositorFrame with a reference to a handle, all it does is post a
task to the IO thread. Now, if this thread continues on and calls Resize, you
may delete the transport dib, which will free the handle before it's been sent
over the wire (and used on the other side). So the other side will try to open /
attach to an invalid handle.

I think you only want to resize TransportDIBs that you "own", that is that you
haven't sent yet and/or have received back.

+  for (size_t i = 0; i < kNumBuffers; i++)
+    dibs_.push_back(CreateDIB());

[piman, 2013/03/29 00:23:53]

From previous review: why not let BeginPaint reallocate the TransportDIB?
There's no much point in pre-allocating, and that lets you get rid of
kNumBuffers which isn't very meaningful (since you can have more buffers than
that). Less code.

+
+  front_buffer_ = 0;
+  num_free_buffers_ = kNumBuffers;
+}
+
+SkCanvas* CompositorSoftwareOutputDevice::BeginPaint(gfx::Rect damage_rect) {
+  DCHECK(CalledOnValidThread());
+
+  if (num_free_buffers_ == 0) {
+    dibs_.insert(dibs_.begin() + front_buffer_, CreateDIB());
+    num_free_buffers_++;
+  }
+
+  TransportDIB* front_dib = dibs_[front_buffer_];
+  DCHECK(front_dib);
+  DCHECK(front_dib->memory());
+
+  // Set up a canvas for the front_dib.
+  bitmap_.setConfig(SkBitmap::kARGB_8888_Config,
+                    viewport_size_.width(),
+                    viewport_size_.height());
+  bitmap_.setPixels(front_dib->memory());
+  device_ = skia::AdoptRef(new SkDevice(bitmap_));
+  canvas_ = skia::AdoptRef(new SkCanvas(device_.get()));
+
+  // Copy damage_rect_ from last_buffer_ to front_buffer_.
+  if (last_buffer_ != -1 && !damage_rect.Contains(damage_rect_)) {
+    DCHECK_EQ(std::abs(front_buffer_ - last_buffer_ - 1) % dibs_.size(), 0u);
+
+    TransportDIB* last_dib = dibs_[last_buffer_];
+    SkBitmap back_bitmap;
+    back_bitmap.setConfig(SkBitmap::kARGB_8888_Config,
+                          viewport_size_.width(),
+                          viewport_size_.height());
+    back_bitmap.setPixels(last_dib->memory());
+
+    SkRect last_damage = gfx::RectToSkRect(damage_rect_);
+    canvas_->drawBitmapRectToRect(back_bitmap, &last_damage, last_damage, NULL);
+  }
+  damage_rect_ = damage_rect;
+
+  return canvas_.get();
+}
+
+void CompositorSoftwareOutputDevice::EndPaint(
+    cc::SoftwareFrameData* frame_data) {
+  DCHECK(CalledOnValidThread());
+  DCHECK_GE(kNumBuffers, dibs_.size());
+
+  if (frame_data) {
+    frame_data->size = viewport_size_;
+    frame_data->damage_rect = damage_rect_;
+    frame_data->dib_id = dibs_[front_buffer_]->id();
+  }
+
+  last_buffer_ = front_buffer_;
+  front_buffer_ = (front_buffer_ + 1) % dibs_.size();
+  --num_free_buffers_;
+  DCHECK_GE(num_free_buffers_, 0);
+}
+
+void CompositorSoftwareOutputDevice::ReclaimDIB(const TransportDIB::Id& id) {
+  DCHECK(CalledOnValidThread());
+
+  // The reclaimed handle might not be among the currently
+  // active dibs if we got a resize event in the mean time.
+  ScopedVector<TransportDIB>::iterator it =
+      std::find_if(dibs_.begin(), dibs_.end(), CompareById(id));
+  if (it != dibs_.end())
+    ++num_free_buffers_;
+
+  DCHECK_LE(static_cast<size_t>(num_free_buffers_), dibs_.size());
+}
+
+}  // namespace content