/**
 * PANDA 3D SOFTWARE
 * Copyright (c) Carnegie Mellon University.  All rights reserved.
 *
 * All use of this software is subject to the terms of the revised BSD
 * license.  You should have received a copy of this license along
 * with this source code in a file named "LICENSE."
 *
 * @file glGraphicsBuffer_src.h
 * @author jyelon
 * @date 2006-01-15
 * @author kleonard
 * @date 2007-06-27
 */

#include "pandabase.h"
#include "graphicsBuffer.h"

/**
 * An offscreen render buffer.
 *
 * The glGraphicsBuffer is based on the OpenGL EXT_framebuffer_object and
 * ARB_draw_buffers extensions.  This design has significant advantages over
 * the older wglGraphicsBuffer and glxGraphicsBuffer:
 *
 * * Can export depth and stencil.  * Supports auxiliary bitplanes.  *
 * Supports non-power-of-two padding.  * Supports tracking of host window
 * size.  * Supports cumulative render-to-texture.  * Faster than pbuffers.  *
 * Can render onto a texture without clearing it first.  * Supports
 * multisample antialiased rendering.
 *
 * Some of these deserve a little explanation.  Auxiliary bitplanes are
 * additional bitplanes above and beyond the normal depth,stencil,color.  One
 * can use them to render out multiple textures in a single pass.  Cumulative
 * render-to-texture means that if don't clear the buffer, then the contents
 * of the buffer will be equal to the texture's previous contents.  This alo
 * means you can meaningfully share a bitplane between two buffers by binding
 * the same texture to both buffers.
 *
 * If either of the necessary OpenGL extensions is not available, then the
 * glGraphicsBuffer will not be available (although it may still be possible
 * to create a wglGraphicsBuffer or glxGraphicsBuffer).
 *
 * This class now also uses the extensions EXT_framebuffer_multisample and
 * EXT_framebuffer_blit to allow for multisample antialiasing these offscreen
 * render targets.  If these extensions are unavailable the buffer will render
 * as if multisamples is 0.
 *
 */
class EXPCL_GL CLP(GraphicsBuffer) : public GraphicsBuffer {
public:
  CLP(GraphicsBuffer)(GraphicsEngine *engine, GraphicsPipe *pipe,
                      const std::string &name,
                      const FrameBufferProperties &fb_prop,
                      const WindowProperties &win_prop,
                      int flags,
                      GraphicsStateGuardian *gsg,
                      GraphicsOutput *host);
  virtual ~CLP(GraphicsBuffer)();

#ifndef OPENGLES
  virtual void clear(Thread *current_thread);
#endif
  virtual bool begin_frame(FrameMode mode, Thread *current_thread);
  virtual void end_frame(FrameMode mode, Thread *current_thread);

  virtual void set_size(int x, int y);

  virtual void select_target_tex_page(int page);

  virtual bool share_depth_buffer(GraphicsOutput *graphics_output);
  virtual void unshare_depth_buffer();

  virtual bool get_supports_render_texture() const;

  void register_shared_depth_buffer(GraphicsOutput *graphics_output);
  void unregister_shared_depth_buffer(GraphicsOutput *graphics_output);

protected:
  virtual GraphicsOutput *get_host();

  virtual void close_buffer();
  virtual bool open_buffer();

  void check_host_valid();

  void report_my_errors(int line, const char *file);

  void bind_slot(int layer, bool rb_resize, Texture **attach,
                 RenderTexturePlane plane, GLenum attachpoint);
  void bind_slot_multisample(bool rb_resize, Texture **attach,
                 RenderTexturePlane plane, GLenum attachpoint);
  void attach_tex(int layer, int view, Texture *attach, GLenum attachpoint);
  bool check_fbo();
  void generate_mipmaps();
  void rebuild_bitplanes();
  void resolve_multisamples();

  // We create one FBO for each cube map face we'll be rendering to.  If we
  // aren't rendering to any cube maps, we use only _fbo[0].
  pvector<GLuint> _fbo;

  // For multisample we render first to a multisample buffer, then filter it
  // to _fbo[face] at the end of the frame.
  GLuint      _fbo_multisample;
  int         _requested_multisamples;
  int         _requested_coverage_samples;
  bool        _use_depth_stencil;
  bool        _have_any_color;

  int         _rb_size_x;
  int         _rb_size_y;
  int         _rb_size_z;

  // Stores the render buffers for each plane.  _rbm stores the multisample
  // renderbuffers.
  GLuint      _rb[RTP_COUNT];
  GLuint      _rbm[RTP_COUNT];

  // For memory tracking of renderbuffers.
  BufferContext *_rb_context;
  size_t _rb_data_size_bytes;

  // List of textures for which we might have to generate mipmaps after
  // rendering one frame.
  typedef pvector<CLP(TextureContext)*> TextureContexts;
  TextureContexts _texture_contexts;

  // The cube map face we are currently drawing to or have just finished
  // drawing to, or -1 if we are not drawing to a cube map.
  int _bound_tex_page;

  bool _initial_clear;
  bool _needs_rebuild;
  UpdateSeq _last_textures_seq;

  CLP(GraphicsBuffer) *_shared_depth_buffer;
  std::list <CLP(GraphicsBuffer) *> _shared_depth_buffer_list;

  PStatCollector _bind_texture_pcollector;
  PStatCollector _generate_mipmap_pcollector;
  PStatCollector _resolve_multisample_pcollector;

public:
  static TypeHandle get_class_type() {
    return _type_handle;
  }
  static void init_type() {
    GraphicsBuffer::init_type();
    register_type(_type_handle, CLASSPREFIX_QUOTED "GraphicsBuffer",
                  GraphicsBuffer::get_class_type());
  }
  virtual TypeHandle get_type() const {
    return get_class_type();
  }
  virtual TypeHandle force_init_type() {init_type(); return get_class_type();}

  INLINE int get_multisample_count();
  INLINE int get_coverage_sample_count();

private:
  static TypeHandle _type_handle;

  friend class CLP(GraphicsStateGuardian);
};

#include "glGraphicsBuffer_src.I"