nvidia glXWaitVideoSync test

wait_video_sync.c

// Build with: gcc wait_video_sync.c -lGLX -lX11 -lGLU -lGL
// Source: https://www.khronos.org/opengl/wiki/Programming_OpenGL_in_Linux:_GLX_and_Xlib

#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glx.h>
#include <GL/glxext.h>
#include <X11/X.h>
#include <X11/Xlib.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

Display *dpy;
Window root;
GLint att[] = {GLX_RGBA, GLX_DEPTH_SIZE, 24, GLX_DOUBLEBUFFER, None};
XVisualInfo *vi;
Colormap cmap;
XSetWindowAttributes swa;
Window win;
GLXContext glc;
XWindowAttributes gwa;
XEvent xev;

PFNGLXWAITVIDEOSYNCSGIPROC glXWaitVideoSyncSGI = NULL;

void DrawAQuad() {
  glClearColor(1.0, 1.0, 1.0, 1.0);
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glOrtho(-1., 1., -1., 1., 1., 20.);

  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  gluLookAt(0., 0., 10., 0., 0., 0., 0., 1., 0.);

  glBegin(GL_QUADS);
  glColor3f(1., 0., 0.);
  glVertex3f(-.75, -.75, 0.);
  glColor3f(0., 1., 0.);
  glVertex3f(.75, -.75, 0.);
  glColor3f(0., 0., 1.);
  glVertex3f(.75, .75, 0.);
  glColor3f(1., 1., 0.);
  glVertex3f(-.75, .75, 0.);
  glEnd();
}

int main(int argc, char *argv[]) {

  dpy = XOpenDisplay(NULL);

  if (dpy == NULL) {
    printf("\n\tcannot connect to X server\n\n");
    exit(0);
  }

  root = DefaultRootWindow(dpy);

  vi = glXChooseVisual(dpy, 0, att);

  if (vi == NULL) {
    printf("\n\tno appropriate visual found\n\n");
    exit(0);
  } else {
    printf("\n\tvisual %p selected\n",
           (void *)vi
               ->visualid); /* %p creates hexadecimal output like in glxinfo */
  }

  cmap = XCreateColormap(dpy, root, vi->visual, AllocNone);

  swa.colormap = cmap;
  swa.event_mask = ExposureMask | KeyPressMask;

  win = XCreateWindow(dpy, root, 0, 0, 600, 600, 0, vi->depth, InputOutput,
                      vi->visual, CWColormap | CWEventMask, &swa);

  XMapWindow(dpy, win);
  XStoreName(dpy, win, "VERY SIMPLE APPLICATION");

  const char *ext = glXQueryExtensionsString(dpy, 0);
  if (!strstr(ext, "GLX_SGI_video_sync")) {
    printf("GLX_SGI_video_sync extension missing\n");
    exit(1);
  }

  glc = glXCreateContext(dpy, vi, NULL, GL_TRUE);
  glXMakeCurrent(dpy, win, glc);
  glXWaitVideoSyncSGI = (PFNGLXWAITVIDEOSYNCSGIPROC)glXGetProcAddress(
      (const GLubyte *)"glXWaitVideoSyncSGI");

  glEnable(GL_DEPTH_TEST);

  while (1) {
    while (XPending(dpy) > 0) {
      XNextEvent(dpy, &xev);

      if (xev.type == Expose) {
        XGetWindowAttributes(dpy, win, &gwa);
        glViewport(0, 0, gwa.width, gwa.height);
      }

      else if (xev.type == KeyPress && xev.xkey.keycode == 0x09) { // ESC
        glXMakeCurrent(dpy, None, NULL);
        glXDestroyContext(dpy, glc);
        XDestroyWindow(dpy, win);
        XCloseDisplay(dpy);
        exit(0);
      }
    }
    DrawAQuad();
    glXSwapBuffers(dpy, win);
    unsigned int count = 0;
    glXWaitVideoSyncSGI(1, 0, &count);
  }
}