/*

Simple Xlib application drawing a box in a window.

gcc input.c -o output -lX11

*/

#include <X11/Xlib.h>

#include <X11/Xutil.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

int main(void) {

Display *d;

Window w;

XEvent e;

char *msg = "Hello, World!";

int s;

/* open connection with the server */

d = XOpenDisplay(NULL);

if (d == NULL) {

fprintf(stderr, "Cannot open display\n");

exit(1);

}

s = DefaultScreen(d);

/* create window */

w = XCreateSimpleWindow(d, RootWindow(d, s), 10, 10, 200, 200, 1,

BlackPixel(d, s), WhitePixel(d, s));

/* select kind of events we are interested in */

XSelectInput(d, w, ExposureMask | KeyPressMask);

XSizeHints *h = XAllocSizeHints();

h->min_aspect.x = 1;

h->min_aspect.y = 2;

h->max_aspect.x = 2;

h->max_aspect.y = 1;

h->flags |= PAspect;

XSetWMNormalHints(d, w, h);

/* map (show) the window */

XMapWindow(d, w);

/* event loop */

while (1) {

XNextEvent(d, &e);

/* draw or redraw the window */

if (e.type == Expose) {

XFillRectangle(d, w, DefaultGC(d, s), 20, 20, 10, 10);

XDrawString(d, w, DefaultGC(d, s), 50, 50, msg, strlen(msg));

}

continue;

/* exit on key press */

if (e.type == KeyPress)

break;

}

/* close connection to server */

XCloseDisplay(d);

return 0;

}