//
// "$Id: gl_start.cxx 8864 2011-07-19 04:49:30Z greg.ercolano $"
//
// OpenGL context routines for the Fast Light Tool Kit (FLTK).
//
// Copyright 1998-2010 by Bill Spitzak and others.
//
// This library is free software. Distribution and use rights are outlined in
// the file "COPYING" which should have been included with this file.  If this
// file is missing or damaged, see the license at:
//
//     http://www.fltk.org/COPYING.php
//
// Please report all bugs and problems on the following page:
//
//     http://www.fltk.org/str.php
//

// You MUST use gl_visual() to select the default visual before doing
// show() of any windows.  Mesa will crash if you try to use a visual
// not returned by glxChooseVisual.

// This does not work with Fl_Double_Window's!  It will try to draw
// into the front buffer.  Depending on the system this will either
// crash or do nothing (when pixmaps are being used as back buffer
// and GL is being done by hardware), work correctly (when GL is done
// with software, such as Mesa), or draw into the front buffer and
// be erased when the buffers are swapped (when double buffer hardware
// is being used)

#include <config.h>
#if HAVE_GL

#include <FL/Fl.H>
#include <FL/Fl_Window.H>
#include <FL/x.H>
#include <FL/fl_draw.H>
#include "Fl_Gl_Choice.H"

static GLContext context;
static int clip_state_number=-1;
static int pw, ph;

#ifdef WIN32
static Fl_Gl_Choice* gl_choice;
#endif

#ifdef __APPLE__
static Fl_Gl_Choice* gl_choice;
#endif

Fl_Region XRectangleRegion(int x, int y, int w, int h); // in fl_rect.cxx

/** Creates an OpenGL context */
void gl_start() {
  if (!context) {
#if defined(USE_X11)
    context = fl_create_gl_context(fl_visual);
#elif defined(WIN32)
    if (!gl_choice) Fl::gl_visual(0);
    context = fl_create_gl_context(Fl_Window::current(), gl_choice);
#elif defined(__APPLE_QUARTZ__)
    // warning: the Quartz version should probably use Core GL (CGL) instead of AGL
    context = fl_create_gl_context(Fl_Window::current(), gl_choice);
#else
#  error Unsupported platform
#endif
  }
  fl_set_gl_context(Fl_Window::current(), context);
#if !defined(WIN32) && !defined(__APPLE__)
  glXWaitX();
#endif
  if (pw != Fl_Window::current()->w() || ph != Fl_Window::current()->h()) {
    pw = Fl_Window::current()->w();
    ph = Fl_Window::current()->h();
    glLoadIdentity();
    glViewport(0, 0, pw, ph);
    glOrtho(0, pw, 0, ph, -1, 1);
    glDrawBuffer(GL_FRONT);
  }
  if (clip_state_number != fl_graphics_driver->fl_clip_state_number) {
    clip_state_number = fl_graphics_driver->fl_clip_state_number;
    int x, y, w, h;
    if (fl_clip_box(0, 0, Fl_Window::current()->w(), Fl_Window::current()->h(),
		    x, y, w, h)) {
      fl_clip_region(XRectangleRegion(x,y,w,h));
      glScissor(x, Fl_Window::current()->h()-(y+h), w, h);
      glEnable(GL_SCISSOR_TEST);
    } else {
      glDisable(GL_SCISSOR_TEST);
    }
  }
}

/** Releases an OpenGL context */
void gl_finish() {
  glFlush();
#if !defined(WIN32) && !defined(__APPLE__)
  glXWaitGL();
#endif
}

int Fl::gl_visual(int mode, int *alist) {
  Fl_Gl_Choice *c = Fl_Gl_Choice::find(mode,alist);
  if (!c) return 0;
#if defined(USE_X11)
  fl_visual = c->vis;
  fl_colormap = c->colormap;
#elif defined(WIN32)
  gl_choice = c;
#elif defined(__APPLE_QUARTZ__)
  // warning: the Quartz version should probably use Core GL (CGL) instead of AGL
  gl_choice = c;
#else
#  error Unsupported platform
#endif
  return 1;
}
#endif

//
// End of "$Id: gl_start.cxx 8864 2011-07-19 04:49:30Z greg.ercolano $".
//
