/*
 * Simple Xlib application drawing a box in a window.
 * gcc input.c -o output -lX11
 */

#include <X11/Xlib.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(void)
{
    Display *display;
    Window window;
    XEvent event;
    char *msg = "Hello, World!";
    int s;

    /* open connection with the server */
    display = XOpenDisplay(NULL);
    if (display == NULL)
    {
        fprintf(stderr, "Cannot open display\n");
        exit(1);
    }

    s = DefaultScreen(display);

    /* create window */
    window = XCreateSimpleWindow(display, RootWindow(display, s), 10, 10, 200, 200, 1,
            BlackPixel(display, s), WhitePixel(display, s));

    /* select kind of events we are interested in */
    XSelectInput(display, window, ExposureMask | KeyPressMask);

    /* map (show) the window */
    XMapWindow(display, window);

    /* event loop */
    for (;;)
    {
        XNextEvent(display, &event);

        /* draw or redraw the window */
        if (event.type == Expose)
        {
            XFillRectangle(display, window, DefaultGC(display, s), 20, 20, 10, 10);
            XDrawString(display, window, DefaultGC(display, s), 50, 50, msg, strlen(msg));
        }
        /* exit on key press */
        if (event.type == KeyPress)
            break;
    }

    /* close connection to server */
    XCloseDisplay(display);

    return 0;
}