#include <stdio.h>
#include <X11/Xlib.h>
#include <GL/glx.h>

/* build: gcc -Wall simple.c -o simple $(pkg-config --cflags --libs gl x11)
   run: for i in {0..300}; do (./simple &); done
*/

int main(int argc, char *argv[])
{
   int width = 128;
   int height = 128;
   int attribs[] = {
      GLX_RGBA,
      GLX_DEPTH_SIZE, 1,
      None
   };
   Display *dpy;
   XVisualInfo *visinfo;
   Pixmap p;
   GLXPixmap g;
   GLXContext glCtx;

   dpy = XOpenDisplay(NULL);
   if (!dpy) {
      fprintf(stderr, "Couldn't open default display\n");
      return 1;
   }

   visinfo = glXChooseVisual(dpy, DefaultScreen(dpy), attribs);
   if (!visinfo) {
      fprintf(stderr, "Failed to select visual\n");
      return 1;
   }

   glCtx = glXCreateContext(dpy, visinfo, 0, True);
   if (!glCtx) {
      fprintf(stderr, "Couldn't create GL context\n");
      return 1;
   }

   p = XCreatePixmap(dpy, DefaultRootWindow(dpy), width,
			  height, visinfo->depth);
   g = glXCreateGLXPixmap(dpy, visinfo, p);

   if (!glXMakeCurrent(dpy, g, glCtx)) {
      fprintf(stderr, "Failed to make context current\n");
      return 1;
   }

   printf("Depth: %d, GL_RENDERER = %s\n", visinfo->depth, (char *) glGetString(GL_RENDERER));

   glViewport(0, 0, width, height);

   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();

   while (1) {
      glClear(GL_COLOR_BUFFER_BIT);
   
      glBegin(GL_POINTS);
      glVertex2i(0, 0);
      glEnd();

      glFlush();
      // same adding glXWaitX();
   }

   return 0;
}