mirror of
https://github.com/flutter/flutter.git
synced 2026-02-20 02:29:02 +08:00
49 lines
1.8 KiB
C++
49 lines
1.8 KiB
C++
// 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.
|
|
|
|
#ifndef FLUTTER_FLOW_LAYERS_OPACITY_LAYER_H_
|
|
#define FLUTTER_FLOW_LAYERS_OPACITY_LAYER_H_
|
|
|
|
#include "flutter/flow/layers/container_layer.h"
|
|
|
|
namespace flutter {
|
|
|
|
// Don't add an OpacityLayer with no children to the layer tree. Painting an
|
|
// OpacityLayer is very costly due to the saveLayer call. If there's no child,
|
|
// having the OpacityLayer or not has the same effect. In debug_unopt build,
|
|
// |Preroll| will assert if there are no children.
|
|
class OpacityLayer : public MergedContainerLayer {
|
|
public:
|
|
// An offset is provided here because OpacityLayer.addToScene method in the
|
|
// Flutter framework can take an optional offset argument.
|
|
//
|
|
// By default, that offset is always zero, and all the offsets are handled by
|
|
// some parent TransformLayers. But we allow the offset to be non-zero for
|
|
// backward compatibility. If it's non-zero, the old behavior is to propage
|
|
// that offset to all the leaf layers (e.g., PictureLayer). That will make
|
|
// the retained rendering inefficient as a small offset change could propagate
|
|
// to many leaf layers. Therefore we try to capture that offset here to stop
|
|
// the propagation as repainting the OpacityLayer is expensive.
|
|
OpacityLayer(SkAlpha alpha, const SkPoint& offset);
|
|
|
|
void Preroll(PrerollContext* context, const SkMatrix& matrix) override;
|
|
|
|
void Paint(PaintContext& context) const override;
|
|
|
|
#if defined(LEGACY_FUCHSIA_EMBEDDER)
|
|
void UpdateScene(SceneUpdateContext& context) override;
|
|
#endif
|
|
|
|
private:
|
|
SkAlpha alpha_;
|
|
SkPoint offset_;
|
|
SkRRect frameRRect_;
|
|
|
|
FML_DISALLOW_COPY_AND_ASSIGN(OpacityLayer);
|
|
};
|
|
|
|
} // namespace flutter
|
|
|
|
#endif // FLUTTER_FLOW_LAYERS_OPACITY_LAYER_H_
|