text: //
  // Copyright 2016 Pixar
  //
  // Licensed under the Apache License, Version 2.0 (the "Apache License")
  // with the following modification; you may not use this file except in
  // compliance with the Apache License and the following modification to it:
  // Section 6. Trademarks. is deleted and replaced with:
  //
  // 6. Trademarks. This License does not grant permission to use the trade
  //    names, trademarks, service marks, or product names of the Licensor
  //    and its affiliates, except as required to comply with Section 4(c) of
  //    the License and to reproduce the content of the NOTICE file.
  //
  // You may obtain a copy of the Apache License at
  //
  //     http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing, software
  // distributed under the Apache License with the above modification is
  // distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  // KIND, either express or implied. See the Apache License for the specific
  // language governing permissions and limitations under the Apache License.
  //
  #ifndef HD_SURFACESHADER_H
  #define HD_SURFACESHADER_H
  
  #include "pxr/imaging/hd/shader.h"
  #include "pxr/imaging/hd/version.h"
  
  #include "pxr/usd/sdf/path.h"
  #include "pxr/base/vt/value.h"
  
  #include "pxr/imaging/garch/gl.h"
  #include "pxr/base/tf/token.h"
  
  #include <boost/shared_ptr.hpp>
  
  #include <vector>
  
  class HdSceneDelegate;
  
  typedef boost::shared_ptr<class HdBufferArrayRange> HdBufferArrayRangeSharedPtr;
  typedef boost::shared_ptr<class HdTextureResource> HdTextureResourceSharedPtr;
  typedef std::vector<HdTextureResourceSharedPtr> HdTextureResourceSharedPtrVector;
  typedef boost::shared_ptr<class HdSurfaceShader> HdSurfaceShaderSharedPtr;
  
  /// A scene-based SurfaceShader object.
  ///
  /// When surface shaders are expresed in the scene graph, the HdSceneDelegate
  /// can use this object to express these surface shaders in Hydra. In addition
  /// to the shader itself, a binding from the Rprim to the SurfaceShader must be
  /// expressed as well.
  class HdSurfaceShader : public HdShader {
  public:
      HdSurfaceShader(HdSceneDelegate* delegate,
                      SdfPath const & id);
  
      virtual ~HdSurfaceShader();
  
      /// Returns the HdSceneDelegate which backs this shader.
      HdSceneDelegate* GetDelegate() const { return _delegate; }
  
      /// Returns the identifer by which this surface shader is known. This
      /// identifier is a common associative key used by the SceneDelegate,
      /// RenderIndex, and for binding to the Rprim.
      SdfPath const& GetID() const { return _id; }
  
      /// Synchronizes state from the delegate to Hydra, for example, allocating
      /// parameters into GPU memory.
      void Sync();
  
      // ---------------------------------------------------------------------- //
      /// \name HdShader Virtual Interface                                      //
      // ---------------------------------------------------------------------- //
      virtual std::string GetSource(TfToken const &shaderStageKey) const;
      virtual HdShaderParamVector const& GetParams() const;
      virtual HdBufferArrayRangeSharedPtr const& GetShaderData() const;
      virtual TextureDescriptorVector GetTextures() const;
      virtual void BindResources(Hd_ResourceBinder const &binder, int program);
      virtual void UnbindResources(Hd_ResourceBinder const &binder, int program);
      virtual void AddBindings(HdBindingRequestVector *customBindings);
      virtual ID ComputeHash() const;
  
      /// Returns if the two shaders can be aggregated in a same drawbatch or not.
      static bool CanAggregate(HdShaderSharedPtr const &shaderA,
                               HdShaderSharedPtr const &shaderB);
  
  protected:
      void _SetSource(TfToken const &shaderStageKey, std::string const &source);
  
  private:
      HdSceneDelegate* _delegate;
      std::string _fragmentSource;
      std::string _geometrySource;
      SdfPath _id;
  
      // Data populated by delegate
      HdBufferArrayRangeSharedPtr _paramArray;
      HdShaderParamVector _params;
  
      TextureDescriptorVector _textureDescriptors;
  };
  
  #endif //HD_SURFACESHADER_H
  