/*

 * 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 */