cc/tiles/paint_worklet_image_cache.cc

// Copyright 2018 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/paint_worklet_image_cache.h"

#include "base/bind.h"
#include "cc/paint/paint_worklet_layer_painter.h"

namespace cc {

class PaintWorkletTaskImpl : public TileTask {
 public:
  PaintWorkletTaskImpl(PaintWorkletImageCache* cache,
                       const PaintImage& paint_image)
      : TileTask(true), cache_(cache), paint_image_(paint_image) {}

  // Overridden from Task:
  void RunOnWorkerThread() override { cache_->PaintImageInTask(paint_image_); }

  // Overridden from TileTask:
  void OnTaskCompleted() override {}

 protected:
  ~PaintWorkletTaskImpl() override = default;

 private:
  PaintWorkletImageCache* cache_;
  PaintImage paint_image_;

  DISALLOW_COPY_AND_ASSIGN(PaintWorkletTaskImpl);
};

PaintWorkletImageCache::PaintWorkletImageCache() {}

PaintWorkletImageCache::~PaintWorkletImageCache() {}

void PaintWorkletImageCache::SetPaintWorkletLayerPainter(
    std::unique_ptr<PaintWorkletLayerPainter> painter) {
  painter_ = std::move(painter);
}

scoped_refptr<TileTask> PaintWorkletImageCache::GetTaskForPaintWorkletImage(
    const DrawImage& image) {
  return base::MakeRefCounted<PaintWorkletTaskImpl>(this, image.paint_image());
}

// TODO(xidachen): dispatch the work to a worklet thread, invoke JS callback.
// Do check the cache first. If there is already a cache entry for this input,
// then there is no need to call the Paint() function.
void PaintWorkletImageCache::PaintImageInTask(const PaintImage& paint_image) {
  sk_sp<PaintRecord> record = painter_->Paint();
  records_[paint_image.paint_worklet_input()] =
      std::make_pair(std::move(record), 0);
}

std::pair<PaintRecord*, base::OnceCallback<void()>>
PaintWorkletImageCache::GetPaintRecordAndRef(PaintWorkletInput* input) {
  records_[input].second++;
  // The PaintWorkletImageCache object lives as long as the LayerTreeHostImpl,
  // and that ensures that this pointer and the input will be alive when this
  // callback is executed.
  auto callback =
      base::BindOnce(&PaintWorkletImageCache::DecrementCacheRefCount,
                     base::Unretained(this), base::Unretained(input));
  return std::make_pair(records_[input].first.get(), std::move(callback));
}

void PaintWorkletImageCache::DecrementCacheRefCount(PaintWorkletInput* input) {
  auto it = records_.find(input);
  DCHECK(it != records_.end());

  auto& pair = it->second;
  DCHECK_GT(pair.second, 0u);
  pair.second--;
}

}  // namespace cc