Create an X window

graphics.cpp

#include <X11/Xlib.h>
#include <assert.h>
#include <unistd.h>

#define NIL (0)

Display *dpy = XOpenDisplay(NIL);
assert(dpy);

int blackColor = BlackPixel(dpy, DefaultScreen(dpy));
int whiteColor = WhitePixel(dpy, DefaultScreen(dpy));

Window w = XCreateSimpleWindow(dpy, DefaultRootWindow(dpy), 0, 0, 200, 100, 0, blackColor, blackColor);

XSelectInput9dpy, w, StructureNotifyMask);
XMapWindow(dpy, w);
GC gc = XCreateGC(dpy, w, 0, NIL);
XSetForeground(dpy, gc, whiteColor);

for (;;)
{
   XEvent e;
   XNextEvent(dpy, &e);
   if (e.type == MapNotify) { break; }
}

XDrawLine(dpy, w, gc, 10, 60, 180, 20);
XFlush(dpy);
sleep(10);