bouncewm.c

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

int main()
{
    Window root;
    Display * dpy;
    XWindowAttributes attr;
    XEvent ev;

    if(!(dpy = XOpenDisplay(0x0))) return 1;

    root = DefaultRootWindow(dpy);

    XGrabButton(dpy, 1, Mod1Mask, root, True, ButtonPressMask, GrabModeAsync,
            GrabModeAsync, None, None);
    int right = 1;
    int up = 1;
    int x = 0;
    int y = 0;
    for(;;)
    {
        XNextEvent(dpy, &ev);
        if(ev.type == ButtonPress && ev.xbutton.subwindow != None)
        {
            XGetWindowAttributes(dpy, ev.xbutton.subwindow, &attr);
            x = 40;
            y = 40;
            for(;;) {
                XMoveWindow(dpy, ev.xbutton.subwindow, x, y);
                XSync(dpy, 0);
                if (x > 1280 - attr.width) {
                    right = 0;
                } else if (x < 0) {
                    right = 1;
                }

                if (y < 0) {
                    up = 1;
                } else if (y > 800 - attr.height) {
                    up = 0;
                }

                x += (right == 1) ? 8 : -6;
                y += (up == 1) ? 6 : -4;
                usleep(50 * 1000);
            }
        }
    }
}