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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 :
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* gcc testdyngl.c `sdl-config --libs --cflags` -o testdyngl -DHAVE_OPENGL
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*
* 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"
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#ifdef __MACOS__
#define HAVE_OPENGL
#endif
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#ifdef HAVE_OPENGL
#include "SDL_opengl.h"
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/* Call this instead of exit(), so we can clean up SDL: atexit() is evil. */
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quit(int rc)
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SDL_Quit();
exit(rc);
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get_funcaddr(const char *p)
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void *f = SDL_GL_GetProcAddress(p);
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if (f) {
return f;
} else {
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printf("Unable to get function pointer for %s\n", p);
quit(1);
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}
return NULL;
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}
typedef struct
{
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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);
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}
glfuncs;
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init_glfuncs(glfuncs * f)
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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");
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}
#define NB_PIXELS 1000
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main(int argc, char *argv[])
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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];
}
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if (SDL_Init(SDL_INIT_VIDEO) < 0) {
printf("Unable to init SDL : %s\n", SDL_GetError());
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return (1);
}
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if (SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1) < 0) {
printf("Unable to set GL attribute : %s\n", SDL_GetError());
quit(1);
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if (SDL_GL_LoadLibrary(gl_library) < 0) {
printf("Unable to dynamically open GL lib : %s\n", SDL_GetError());
quit(1);
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if (SDL_SetVideoMode(640, 480, 0, SDL_OPENGL) == NULL) {
printf("Unable to open video mode : %s\n", SDL_GetError());
quit(1);
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}
/* Set the window manager title bar */
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SDL_WM_SetCaption("SDL Dynamic OpenGL Loading Test", "testdyngl");
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init_glfuncs(&f);
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for (i = 0; i < NB_PIXELS; i++) {
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pixels[3 * i] = rand() % 250 - 125;
pixels[3 * i + 1] = rand() % 250 - 125;
pixels[3 * i + 2] = rand() % 250 - 125;
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f.glViewport(0, 0, 640, 480);
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f.glMatrixMode(GL_PROJECTION);
f.glLoadIdentity();
f.glOrtho(-100, 100, -100, 100, -500, 500);
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f.glMatrixMode(GL_MODELVIEW);
f.glLoadIdentity();
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f.glEnable(GL_DEPTH_TEST);
f.glDisable(GL_TEXTURE_2D);
f.glEnable(GL_BLEND);
f.glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
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f.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
f.glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
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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);
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f.glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
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f.glRotatef(2.0, 1.0, 1.0, 1.0);
f.glRotatef(1.0, 0.0, 1.0, 1.0);
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f.glColor4ub(255, 255, 255, 255);
f.glBegin(GL_POINTS);
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for (i = 0; i < NB_PIXELS; i++) {
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f.glVertex3f(pixels[3 * i], pixels[3 * i + 1], pixels[3 * i + 2]);
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f.glEnd();
SDL_GL_SwapBuffers();
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while (SDL_PollEvent(&event)) {
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if (event.type & SDL_KEYDOWN)
done = 1;
}
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SDL_Delay(20);
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}
while (!done);
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SDL_Quit();
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}
#else /* HAVE_OPENGL */
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main(int argc, char *argv[])
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printf("No OpenGL support on this system\n");
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}
#endif /* HAVE_OPENGL */