xlib-resize.c

// clang -Wall -L/usr/X11R6/lib -lX11 -o xlib-resize xlib-resize.c

#include <X11/Xlib.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;

   d = XOpenDisplay(NULL);
   if (d == NULL) {
      fprintf(stderr, "Cannot open display\n");
      exit(1);
   }

   int x = 10, y = 10, width = 100, height = 100;

   s = DefaultScreen(d);
   w = XCreateSimpleWindow(d, RootWindow(d, s), x, y, width, height, 1,
                           BlackPixel(d, s), WhitePixel(d, s));
   XSelectInput(d, w, ExposureMask | KeyPressMask);
   XMapWindow(d, w);

   printf("press any key to resize\n");

   while (1) {
      XNextEvent(d, &e);
      if (e.type == Expose) {
         XFillRectangle(d, w, DefaultGC(d, s), 20, 20, 10, 10);
         XDrawString(d, w, DefaultGC(d, s), 10, 50, msg, strlen(msg));
      }
      if (e.type == KeyPress) {
          printf("resizing window\n");
          x += 10;
          y += 10;
          width += 20;
          height += 20;
          XMoveResizeWindow(d, w, x, y, width, height);
      }
   }

   XCloseDisplay(d);
   return 0;
}