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// Copyright 2014 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef COBALT_RENDER_TREE_BRUSH_VISITOR_H_
#define COBALT_RENDER_TREE_BRUSH_VISITOR_H_
namespace cobalt {
namespace render_tree {
class LinearGradientBrush;
class RadialGradientBrush;
class SolidColorBrush;
// Type-safe branching on a class hierarchy of render tree brushes,
// implemented after a classical GoF pattern (see
// http://en.wikipedia.org/wiki/Visitor_pattern#Java_example).
//
// Usage example:
//
// class ShaderFactory : public BrushVisitor {
// SkShader* shader() {
// return shader_;
// }
//
// void Visit(SolidColorBrush* solid_color_brush) OVERRIDE {
// shader_ = new SkColorShader(...);
// }
//
// void Visit(LinearGradientBrush* linear_gradient_brush) OVERRIDE {
// shader_ = new SkGradientShader(...);
// }
//
// void Visit(RadialGradientBrush* radial_gradient_brush) OVERRIDE {
// shader_ = new SkGradientShader(...);
// }
// };
//
// ShaderFactory shader_factory;
// render_tree_rect->background_brush().Accept(&shader_factory);
// paint.setShader(shader_factory.shader());
//
class BrushVisitor {
public:
virtual void Visit(const SolidColorBrush* solid_color_brush) = 0;
virtual void Visit(const LinearGradientBrush* linear_gradient_brush) = 0;
virtual void Visit(const RadialGradientBrush* radial_gradient_brush) = 0;
protected:
~BrushVisitor() {}
};
} // namespace render_tree
} // namespace cobalt
#endif // COBALT_RENDER_TREE_BRUSH_VISITOR_H_