1// Copyright 2013 The Flutter Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef FLUTTER_FLOW_LAYERS_IMAGE_FILTER_LAYER_H_
6#define FLUTTER_FLOW_LAYERS_IMAGE_FILTER_LAYER_H_
7
8#include "flutter/flow/layers/container_layer.h"
9
10#include "third_party/skia/include/core/SkImageFilter.h"
11
12namespace flutter {
13
14class ImageFilterLayer : public MergedContainerLayer {
15 public:
16 ImageFilterLayer(sk_sp<SkImageFilter> filter);
17
18 void Preroll(PrerollContext* context, const SkMatrix& matrix) override;
19
20 void Paint(PaintContext& context) const override;
21
22 private:
23 // The ImageFilterLayer might cache the filtered output of this layer
24 // if the layer remains stable (if it is not animating for instance).
25 // If the ImageFilterLayer is not the same between rendered frames,
26 // though, it will cache its children instead and filter their cached
27 // output on the fly.
28 // Caching just the children saves the time to render them and also
29 // avoids a rendering surface switch to draw them.
30 // Caching the layer itself avoids all of that and additionally avoids
31 // the cost of applying the filter, but can be worse than caching the
32 // children if the filter itself is not stable from frame to frame.
33 // This constant controls how many times we will Preroll and Paint this
34 // same ImageFilterLayer before we consider the layer and filter to be
35 // stable enough to switch from caching the children to caching the
36 // filtered output of this layer.
37 static constexpr int kMinimumRendersBeforeCachingFilterLayer = 3;
38
39 sk_sp<SkImageFilter> filter_;
40 sk_sp<SkImageFilter> transformed_filter_;
41 int render_count_;
42
43 FML_DISALLOW_COPY_AND_ASSIGN(ImageFilterLayer);
44};
45
46} // namespace flutter
47
48#endif // FLUTTER_FLOW_LAYERS_IMAGE_FILTER_LAYER_H_
49