testdyngl.c
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/*
* 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
*
* 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"
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);
exit(1);
}
}
typedef struct
{
void(*glBegin)(GLenum);
void(*glEnd)();
void(*glVertex3f)(GLfloat, GLfloat, GLfloat);
void(*glClearColor)(GLfloat, GLfloat, GLfloat, GLfloat);
void(*glClear)(GLbitfield);
void(*glDisable)(GLenum);
void(*glEnable)(GLenum);
void(*glColor4ub)(GLubyte,GLubyte,GLubyte,GLubyte);
void(*glPointSize)(GLfloat);
void(*glHint)(GLenum,GLenum);
void(*glBlendFunc)(GLenum,GLenum);
void(*glMatrixMode)(GLenum);
void(*glLoadIdentity)();
void(*glOrtho)(GLdouble,GLdouble,GLdouble,GLdouble,GLdouble,GLdouble);
void(*glRotatef)(GLfloat,GLfloat,GLfloat,GLfloat);
void(*glViewport)(GLint,GLint,GLsizei,GLsizei);
void(*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];
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#ifdef _WIN32
char *gl_library = "OpenGL32.DLL";
#else
char *gl_library = "libGL.so.1";
#endif
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if (argv[1]) {
gl_library = argv[1];
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if (SDL_Init(SDL_INIT_VIDEO)<0)
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{
printf("Unable to init SDL : %s\n",SDL_GetError());
exit(1);
}
if (SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER,1)<0)
{
printf("Unable to set GL attribute : %s\n",SDL_GetError());
exit(1);
}
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if (SDL_GL_LoadLibrary(gl_library)<0)
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{
printf("Unable to dynamically open GL lib : %s\n",SDL_GetError());
exit(1);
}
if (SDL_SetVideoMode(640,480,0,SDL_OPENGL)==NULL)
{
printf("Unable to open video mode : %s\n",SDL_GetError());
exit(1);
}
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 */