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// Copyright 2013 The Flutter 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 <memory>
#include <unordered_map>
#include "flutter/flow/instrumentation.h"
#include "flutter/flow/raster_cache_key.h"
#include "flutter/fml/macros.h"
#include "flutter/fml/memory/weak_ptr.h"
#include "third_party/skia/include/core/SkImage.h"
#include "third_party/skia/include/core/SkSize.h"
namespace flutter {
class RasterCacheResult {
RasterCacheResult() = default;
RasterCacheResult(const RasterCacheResult& other) = default;
RasterCacheResult(sk_sp<SkImage> image, const SkRect& logical_rect);
operator bool() const { return static_cast<bool>(image_); }
bool is_valid() const { return static_cast<bool>(image_); };
void draw(SkCanvas& canvas, const SkPaint* paint = nullptr) const;
SkISize image_dimensions() const {
return image_ ? image_->dimensions() : SkISize::Make(0, 0);
sk_sp<SkImage> image_;
SkRect logical_rect_;
struct PrerollContext;
class RasterCache {
// The default max number of picture raster caches to be generated per frame.
// Generating too many caches in one frame may cause jank on that frame. This
// limit allows us to throttle the cache and distribute the work across
// multiple frames.
static constexpr int kDefaultPictureCacheLimitPerFrame = 3;
explicit RasterCache(
size_t access_threshold = 3,
size_t picture_cache_limit_per_frame = kDefaultPictureCacheLimitPerFrame);
static SkIRect GetDeviceBounds(const SkRect& rect, const SkMatrix& ctm) {
SkRect device_rect;
ctm.mapRect(&device_rect, rect);
SkIRect bounds;
return bounds;
* @brief Snap the translation components of the matrix to integers.
* The snapping will only happen if the matrix only has scale and translation
* transformations.
* @param ctm the current transformation matrix.
* @return SkMatrix the snapped transformation matrix.
static SkMatrix GetIntegralTransCTM(const SkMatrix& ctm) {
// Avoid integral snapping if the matrix has complex transformation to avoid
// the artifact observed in
if (!ctm.isScaleTranslate()) {
return ctm;
SkMatrix result = ctm;
result[SkMatrix::kMTransX] = SkScalarRoundToScalar(ctm.getTranslateX());
result[SkMatrix::kMTransY] = SkScalarRoundToScalar(ctm.getTranslateY());
return result;
// Return true if the cache is generated.
// We may return false and not generate the cache if
// 1. The picture is not worth rasterizing
// 2. The matrix is singular
// 3. The picture is accessed too few times
// 4. There are too many pictures to be cached in the current frame.
// (See also kDefaultPictureCacheLimitPerFrame.)
bool Prepare(GrContext* context,
SkPicture* picture,
const SkMatrix& transformation_matrix,
SkColorSpace* dst_color_space,
bool is_complex,
bool will_change);
void Prepare(PrerollContext* context, Layer* layer, const SkMatrix& ctm);
// Find the raster cache for the picture and draw it to the canvas.
// Return true if it's found and drawn.
bool Draw(const SkPicture& picture, SkCanvas& canvas) const;
// Find the raster cache for the layer and draw it to the canvas.
// Addional paint can be given to change how the raster cache is drawn (e.g.,
// draw the raster cache with some opacity).
// Return true if the layer raster cache is found and drawn.
bool Draw(const Layer* layer,
SkCanvas& canvas,
SkPaint* paint = nullptr) const;
void SweepAfterFrame();
void Clear();
void SetCheckboardCacheImages(bool checkerboard);
size_t GetCachedEntriesCount() const;
struct Entry {
bool used_this_frame = false;
size_t access_count = 0;
RasterCacheResult image;
template <class Cache>
static void SweepOneCacheAfterFrame(Cache& cache) {
std::vector<typename Cache::iterator> dead;
for (auto it = cache.begin(); it != cache.end(); ++it) {
Entry& entry = it->second;
if (!entry.used_this_frame) {
entry.used_this_frame = false;
for (auto it : dead) {
const size_t access_threshold_;
const size_t picture_cache_limit_per_frame_;
size_t picture_cached_this_frame_ = 0;
mutable PictureRasterCacheKey::Map<Entry> picture_cache_;
mutable LayerRasterCacheKey::Map<Entry> layer_cache_;
bool checkerboard_images_;
void TraceStatsToTimeline() const;
} // namespace flutter