cc/tiles/image_decode_controller.cc

// Copyright 2015 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/tiles/image_decode_controller.h"

#include <stdint.h>

#include "base/macros.h"
#include "cc/debug/devtools_instrumentation.h"

namespace cc {
namespace {

class ImageDecodeTaskImpl : public ImageDecodeTask {
 public:
  ImageDecodeTaskImpl(ImageDecodeController* controller,
                      const SkImage* image,
                      int layer_id,
                      uint64_t source_prepare_tiles_id)
      : controller_(controller),
        image_(skia::SharePtr(image)),
        layer_id_(layer_id),
        source_prepare_tiles_id_(source_prepare_tiles_id) {}

  // Overridden from Task:
  void RunOnWorkerThread() override {
    TRACE_EVENT1("cc", "ImageDecodeTaskImpl::RunOnWorkerThread",
                 "source_prepare_tiles_id", source_prepare_tiles_id_);
    devtools_instrumentation::ScopedImageDecodeTask image_decode_task(
        image_.get());
    controller_->DecodeImage(image_.get());

    // Release the reference after decoding image to ensure that it is not kept
    // alive unless needed.
    image_.clear();
  }

  // Overridden from TileTask:
  void ScheduleOnOriginThread(TileTaskClient* client) override {}
  void CompleteOnOriginThread(TileTaskClient* client) override {
    controller_->OnImageDecodeTaskCompleted(layer_id_, image_.get(),
                                            !HasFinishedRunning());
  }

 protected:
  ~ImageDecodeTaskImpl() override {}

 private:
  ImageDecodeController* controller_;
  skia::RefPtr<const SkImage> image_;
  int layer_id_;
  uint64_t source_prepare_tiles_id_;

  DISALLOW_COPY_AND_ASSIGN(ImageDecodeTaskImpl);
};

}  // namespace

ImageDecodeController::ImageDecodeController() {}

ImageDecodeController::~ImageDecodeController() {}

scoped_refptr<ImageDecodeTask> ImageDecodeController::GetTaskForImage(
    const DrawImage& image,
    int layer_id,
    uint64_t prepare_tiles_id) {
  uint32_t generation_id = image.image()->uniqueID();
  scoped_refptr<ImageDecodeTask>& decode_task =
      image_decode_tasks_[layer_id][generation_id];
  if (!decode_task)
    decode_task = CreateTaskForImage(image.image(), layer_id, prepare_tiles_id);
  return decode_task;
}

scoped_refptr<ImageDecodeTask> ImageDecodeController::CreateTaskForImage(
    const SkImage* image,
    int layer_id,
    uint64_t prepare_tiles_id) {
  return make_scoped_refptr(
      new ImageDecodeTaskImpl(this, image, layer_id, prepare_tiles_id));
}

void ImageDecodeController::DecodeImage(const SkImage* image) {
  image->preroll();
}

void ImageDecodeController::AddLayerUsedCount(int layer_id) {
  ++used_layer_counts_[layer_id];
}

void ImageDecodeController::SubtractLayerUsedCount(int layer_id) {
  if (--used_layer_counts_[layer_id])
    return;

  // Clean up decode tasks once a layer is no longer used.
  used_layer_counts_.erase(layer_id);
  image_decode_tasks_.erase(layer_id);
}

void ImageDecodeController::OnImageDecodeTaskCompleted(int layer_id,
                                                       const SkImage* image,
                                                       bool was_canceled) {
  // If the task has successfully finished, then keep the task until the layer
  // is no longer in use. This ensures that we only decode a image once.
  // TODO(vmpstr): Remove this when decode lifetime is controlled by cc.
  if (!was_canceled)
    return;

  // Otherwise, we have to clean up the task so that a new one can be created if
  // we need to decode the image again.
  LayerImageTaskMap::iterator layer_it = image_decode_tasks_.find(layer_id);
  if (layer_it == image_decode_tasks_.end())
    return;

  ImageTaskMap& image_tasks = layer_it->second;
  ImageTaskMap::iterator task_it = image_tasks.find(image->uniqueID());
  if (task_it == image_tasks.end())
    return;
  image_tasks.erase(task_it);
}

}  // namespace cc