/*
  Copyright (C) 1997-2011 Sam Lantinga <slouken@libsdl.org>

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely.
*/
/*
 * Small SDL example to demonstrate dynamically loading 
 * OpenGL lib and functions
 *
 * (FYI it was supposed to look like snow in the wind or something...)
 *
 * Compile with :
 * gcc testdyngl.c `sdl-config --libs --cflags` -o testdyngl -DHAVE_OPENGL
 *
 * You can specify a different OpenGL lib on the command line, i.e. :
 * ./testdyngl  /usr/X11R6/lib/libGL.so.1.2
 * or
 * ./testdyngl  /usr/lib/libGL.so.1.0.4496
 *
 */

#include <stdio.h>
#include <stdlib.h>

#include "SDL.h"

#ifdef __MACOS__
#define HAVE_OPENGL
#endif

#ifdef HAVE_OPENGL

#include "SDL_opengl.h"

/* Call this instead of exit(), so we can clean up SDL: atexit() is evil. */
static void
quit(int rc)
{
    SDL_Quit();
    exit(rc);
}

void *
get_funcaddr(const char *p)
{
    void *f = SDL_GL_GetProcAddress(p);
    if (f) {
        return f;
    } else {
        printf("Unable to get function pointer for %s\n", p);
        quit(1);
    }
    return NULL;
}

typedef struct
{
    void (APIENTRY * glBegin) (GLenum);
    void (APIENTRY * glEnd) ();
    void (APIENTRY * glVertex3f) (GLfloat, GLfloat, GLfloat);
    void (APIENTRY * glClearColor) (GLfloat, GLfloat, GLfloat, GLfloat);
    void (APIENTRY * glClear) (GLbitfield);
    void (APIENTRY * glDisable) (GLenum);
    void (APIENTRY * glEnable) (GLenum);
    void (APIENTRY * glColor4ub) (GLubyte, GLubyte, GLubyte, GLubyte);
    void (APIENTRY * glPointSize) (GLfloat);
    void (APIENTRY * glHint) (GLenum, GLenum);
    void (APIENTRY * glBlendFunc) (GLenum, GLenum);
    void (APIENTRY * glMatrixMode) (GLenum);
    void (APIENTRY * glLoadIdentity) ();
    void (APIENTRY * glOrtho) (GLdouble, GLdouble, GLdouble, GLdouble,
                               GLdouble, GLdouble);
    void (APIENTRY * glRotatef) (GLfloat, GLfloat, GLfloat, GLfloat);
    void (APIENTRY * glViewport) (GLint, GLint, GLsizei, GLsizei);
    void (APIENTRY * glFogf) (GLenum, GLfloat);
    const GLubyte* (APIENTRY * glGetString) (GLenum);
}
glfuncs;

void
init_glfuncs(glfuncs * f)
{
    f->glBegin = get_funcaddr("glBegin");
    f->glEnd = get_funcaddr("glEnd");
    f->glVertex3f = get_funcaddr("glVertex3f");
    f->glClearColor = get_funcaddr("glClearColor");
    f->glClear = get_funcaddr("glClear");
    f->glDisable = get_funcaddr("glDisable");
    f->glEnable = get_funcaddr("glEnable");
    f->glColor4ub = get_funcaddr("glColor4ub");
    f->glPointSize = get_funcaddr("glPointSize");
    f->glHint = get_funcaddr("glHint");
    f->glBlendFunc = get_funcaddr("glBlendFunc");
    f->glMatrixMode = get_funcaddr("glMatrixMode");
    f->glLoadIdentity = get_funcaddr("glLoadIdentity");
    f->glOrtho = get_funcaddr("glOrtho");
    f->glRotatef = get_funcaddr("glRotatef");
    f->glViewport = get_funcaddr("glViewport");
    f->glFogf = get_funcaddr("glFogf");
    f->glGetString = get_funcaddr("glGetString");

    printf("Vendor     : %s\n", f->glGetString(GL_VENDOR));
    printf("Renderer   : %s\n", f->glGetString(GL_RENDERER));
    printf("Version    : %s\n", f->glGetString(GL_VERSION));
    printf("Extensions : %s\n", f->glGetString(GL_EXTENSIONS));
}

#define NB_PIXELS 1000

int
main(int argc, char *argv[])
{
    glfuncs f;
    int i;
    SDL_Event event;
    int done = 0;
    GLfloat pixels[NB_PIXELS * 3];
    const char *gl_library = NULL;      /* Use the default GL library */

    if (argv[1]) {
        gl_library = argv[1];
    }

    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
        printf("Unable to init SDL : %s\n", SDL_GetError());
        return (1);
    }

    if (SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1) < 0) {
        printf("Unable to set GL attribute : %s\n", SDL_GetError());
        quit(1);
    }

    if (SDL_GL_LoadLibrary(gl_library) < 0) {
        printf("Unable to dynamically open GL lib : %s\n", SDL_GetError());
        quit(1);
    }

    if (SDL_SetVideoMode(640, 480, 0, SDL_OPENGL) == NULL) {
        printf("Unable to open video mode : %s\n", SDL_GetError());
        quit(1);
    }

    /* Set the window manager title bar */
    SDL_WM_SetCaption("SDL Dynamic OpenGL Loading Test", "testdyngl");

    init_glfuncs(&f);

    for (i = 0; i < NB_PIXELS; i++) {
        pixels[3 * i] = rand() % 250 - 125;
        pixels[3 * i + 1] = rand() % 250 - 125;
        pixels[3 * i + 2] = rand() % 250 - 125;
    }

    f.glViewport(0, 0, 640, 480);

    f.glMatrixMode(GL_PROJECTION);
    f.glLoadIdentity();
    f.glOrtho(-100, 100, -100, 100, -500, 500);

    f.glMatrixMode(GL_MODELVIEW);
    f.glLoadIdentity();

    f.glEnable(GL_DEPTH_TEST);
    f.glDisable(GL_TEXTURE_2D);
    f.glEnable(GL_BLEND);
    f.glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

    f.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
    f.glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    f.glEnable(GL_POINT_SMOOTH);
    f.glHint(GL_POINT_SMOOTH_HINT, GL_NICEST);
    f.glPointSize(5.0f);
    f.glEnable(GL_FOG);
    f.glFogf(GL_FOG_START, -500);
    f.glFogf(GL_FOG_END, 500);
    f.glFogf(GL_FOG_DENSITY, 0.005);

    do {
        f.glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        f.glRotatef(2.0, 1.0, 1.0, 1.0);
        f.glRotatef(1.0, 0.0, 1.0, 1.0);

        f.glColor4ub(255, 255, 255, 255);
        f.glBegin(GL_POINTS);
        for (i = 0; i < NB_PIXELS; i++) {
            f.glVertex3f(pixels[3 * i], pixels[3 * i + 1], pixels[3 * i + 2]);
        }
        f.glEnd();
        SDL_GL_SwapBuffers();

        while (SDL_PollEvent(&event)) {
            if (event.type == SDL_KEYDOWN)
                done = 1;
        }

        SDL_Delay(20);
    } while (!done);

    SDL_Quit();
    return 0;
}

#else /* HAVE_OPENGL */

int
main(int argc, char *argv[])
{
    printf("No OpenGL support on this system\n");
    return 1;
}

#endif /* HAVE_OPENGL */