text: // ----------------------------------------------------------------------------
  // -                        Open3D: www.open3d.org                            -
  // ----------------------------------------------------------------------------
  // The MIT License (MIT)
  //
  // Copyright (c) 2020 www.open3d.org
  //
  // Permission is hereby granted, free of charge, to any person obtaining a copy
  // of this software and associated documentation files (the "Software"), to deal
  // in the Software without restriction, including without limitation the rights
  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  // copies of the Software, and to permit persons to whom the Software is
  // furnished to do so, subject to the following conditions:
  //
  // The above copyright notice and this permission notice shall be included in
  // all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  // FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  // IN THE SOFTWARE.
  // ----------------------------------------------------------------------------
  
  #pragma once
  
  #include "Open3D/Visualization/Rendering/RenderToBuffer.h"
  
  namespace filament {
  class Engine;
  class Renderer;
  class Scene;
  class SwapChain;
  }  // namespace filament
  
  namespace open3d {
  namespace visualization {
  
  class FilamentRenderer;
  class FilamentScene;
  class FilamentView;
  
  class FilamentRenderToBuffer : public RenderToBuffer {
  public:
      // Use Renderer::CreateBufferRenderer to instantiate
      // FilamentRenderToBuffer, unless you are NOT using open3d::gui or
      // another FilamentRenderer instance.
      explicit FilamentRenderToBuffer(filament::Engine& engine);
      FilamentRenderToBuffer(filament::Engine& engine, FilamentRenderer& parent);
      ~FilamentRenderToBuffer() override;
  
      void SetDimensions(std::size_t width, std::size_t height) override;
      void CopySettings(const View* view) override;
      View& GetView() override;
  
      void RequestFrame(Scene* scene, BufferReadyCallback cb) override;
  
  private:
      friend class FilamentRenderer;
  
      FilamentRenderer* parent_ = nullptr;
      filament::Engine& engine_;
      filament::Renderer* renderer_ = nullptr;
      filament::SwapChain* swapchain_ = nullptr;
      FilamentView* view_ = nullptr;
  
      std::size_t width_ = 0;
      std::size_t height_ = 0;
      std::uint8_t* buffer_ = nullptr;
      std::size_t buffer_size_ = 0;
  
      BufferReadyCallback callback_;
      bool frame_done_ = true;
      bool pending_ = false;
  
      static void ReadPixelsCallback(void* buffer, size_t size, void* user);
      void Render();
  };
  
  }  // namespace visualization
  }  // namespace open3d
  