/*

 * 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);

}

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");

}

#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 */