blob: 658dd1a7b84886445cdcb5c95c3e69261b287b9a [file] [log] [blame]
// 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 "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 ContainerLayer {
// 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 Add(std::shared_ptr<Layer> layer) override;
void Preroll(PrerollContext* context, const SkMatrix& matrix) override;
void Paint(PaintContext& context) const override;
#if defined(OS_FUCHSIA)
void UpdateScene(SceneUpdateContext& context) override;
#endif // defined(OS_FUCHSIA)
ContainerLayer* GetChildContainer() const;
SkAlpha alpha_;
SkPoint offset_;
SkRRect frameRRect_;
} // namespace flutter