text: 
  //
  // This source file is part of appleseed.
  // Visit https://appleseedhq.net/ for additional information and resources.
  //
  // This software is released under the MIT license.
  //
  // Copyright (c) 2010-2013 Francois Beaune, Jupiter Jazz Limited
  // Copyright (c) 2014-2018 Francois Beaune, The appleseedhq Organization
  //
  // 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
  
  // appleseed.foundation headers.
  #include "foundation/core/concepts/iunknown.h"
  
  // appleseed.main headers.
  #include "main/dllsymbol.h"
  
  // Forward declarations.
  namespace foundation    { class IAbortSwitch; }
  namespace foundation    { class JobQueue; }
  namespace renderer      { class Frame; }
  
  namespace renderer
  {
  
  //
  // Pass callback interface.
  //
  // Used by the generic frame renderer in multi-pass mode.
  //
  
  class APPLESEED_DLLSYMBOL IPassCallback
    : public foundation::IUnknown
  {
    public:
      // This method is called at the beginning of a pass.
      virtual void on_pass_begin(
          const Frame&                frame,
          foundation::JobQueue&       job_queue,
          foundation::IAbortSwitch&   abort_switch) = 0;
  
      // This method is called at the end of a pass.
      virtual void on_pass_end(
          const Frame&                frame,
          foundation::JobQueue&       job_queue,
          foundation::IAbortSwitch&   abort_switch) = 0;
  };
  
  }   // namespace renderer
  