/*

  * 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 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);

 	}

 }

 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];

 #if defined(__IRIX__)

 	const char *gl_library = "libGL.so";

 #elif defined(__MACOSX__)

 	const char *gl_library = "/usr/X11R6/lib/libGL.1.dylib";

 #elif defined(__QNXNTO__)

 	const char *gl_library = "libGL.so.3";

 #elif defined(__WIN32__)

 	const char *gl_library = "OpenGL32.DLL";

 #else

 	const char *gl_library = "libGL.so.1";

 #endif

 	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 */