Table of contents
11.1.2010
Creating an OpenGL 3 context with GLX
This might be well-known by now, but when I was creating my OpenGL 3.0 contexts for the first time, information online was scarce, or at the very least hard to find.
Anyway, this is how to create an OpenGL 3.2 (works for any 3.x) context with just the GLX:
#define GL_GLEXT_PROTOTYPES
#define GLX_GLXEXT_PROTOTYPES
#include <X11/Xlib.h>
#include <GL/gl.h>
#include <GL/glx.h>
// These are obsolete in most distributions, hence provided explicitly.
#include "GL/glxext.h"
#include "GL/glext.h"
Display *d_dpy;
Window d_win;
GLXContext d_ctx;
// Set to NULL for getting it from the environment variable
const char *display = ":0";
int width = 2560;
int height = 1600;
if (!(d_dpy = XOpenDisplay(display))) {
throw std::string("Couldn't open X11 display\n");
}
int attr[] = {
GLX_RGBA,
GLX_RED_SIZE, 1,
GLX_GREEN_SIZE, 1,
GLX_BLUE_SIZE, 1,
GLX_DOUBLEBUFFER,
GLX_DEPTH_SIZE, 1,
None
};
int scrnum = DefaultScreen(d_dpy);
Window root = RootWindow(d_dpy, scrnum);
// We need this for OpenGL3
int elemc;
GLXFBConfig *fbcfg = glXChooseFBConfig(d_dpy, scrnum, NULL, &elemc);
if (!fbcfg)
throw std::string("Couldn't get FB configs\n");
else
printf("Got %d FB configs\n", elemc);
XVisualInfo *visinfo = glXChooseVisual(d_dpy, scrnum, attr);
if (!visinfo)
throw std::string("Couldn't get a visual\n");
// Window parameters
XSetWindowAttributes winattr;
winattr.background_pixel = 0;
winattr.border_pixel = 0;
winattr.colormap = XCreateColormap(d_dpy, root, visinfo->visual, AllocNone);
winattr.event_mask = StructureNotifyMask | ExposureMask | KeyPressMask;
unsigned long mask = CWBackPixel | CWBorderPixel | CWColormap | CWEventMask;
printf("Window depth %d, w %d h %d\n", visinfo->depth, width, height);
d_win = XCreateWindow(d_dpy, root, 0, 0, width, height, 0,
visinfo->depth, InputOutput, visinfo->visual, mask, &winattr);
// OpenGL 3.2
int gl3attr[] = {
GLX_CONTEXT_MAJOR_VERSION_ARB, 3,
GLX_CONTEXT_MINOR_VERSION_ARB, 2,
GLX_CONTEXT_FLAGS_ARB, GLX_CONTEXT_FORWARD_COMPATIBLE_BIT_ARB,
None
};
d_ctx = glXCreateContextAttribsARB(d_dpy, fbcfg[0], NULL, true, gl3attr);
XFree(visinfo);
XMapWindow(d_dpy, d_win);
glXMakeCurrent(d_dpy, d_win, d_ctx);
printf("OpenGL:\n\tvendor %s\n\trenderer %s\n\tversion %s\n\tshader language %s\n\textensions %s\n",
glGetString(GL_VENDOR), glGetString(GL_RENDERER), glGetString(GL_VERSION),
glGetString(GL_SHADING_LANGUAGE_VERSION), glGetString(GL_EXTENSIONS));
int texunits;
glGetIntegerv(GL_MAX_TEXTURE_IMAGE_UNITS, &texunits);
printf("\t%d texture mapping units\n", texunits);
glViewport(0, 0, width, height);
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