--- /dev/null
+#include <stdio.h>
+#include <X11/Xlib.h>
+#include <X11/Xutil.h>
+#include <X11/Xatom.h>
+
+int main () {
+ Display *display;
+ Window parent, child;
+ XEvent report;
+ Atom state, modal;
+ int x=10,y=10,h=400,w=400;
+ XEvent ce;
+
+ display = XOpenDisplay(NULL);
+
+ if (display == NULL) {
+ fprintf(stderr, "couldn't connect to X server :0\n");
+ return 0;
+ }
+
+ state = XInternAtom(display, "_NET_WM_STATE", True);
+ modal = XInternAtom(display, "_NET_WM_STATE_MODAL", True);
+
+ parent = XCreateWindow(display, RootWindow(display, 0),
+ x, y, w, h, 10, CopyFromParent, CopyFromParent,
+ CopyFromParent, 0, 0);
+ child = XCreateWindow(display, RootWindow(display, 0),
+ x, y, w/2, h/2, 10, CopyFromParent, CopyFromParent,
+ CopyFromParent, 0, 0);
+
+ XSetWindowBackground(display,parent,WhitePixel(display,0));
+ XSetWindowBackground(display,child,BlackPixel(display,0));
+
+ XSetTransientForHint(display, child, parent);
+
+ XMapWindow(display, parent);
+ XMapWindow(display, child);
+ XFlush(display);
+
+ ce.xclient.type = ClientMessage;
+ ce.xclient.message_type = state;
+ ce.xclient.display = display;
+ ce.xclient.window = child;
+ ce.xclient.format = 32;
+ ce.xclient.data.l[0] = 1;
+ ce.xclient.data.l[1] = modal;
+ ce.xclient.data.l[2] = 0;
+ XSendEvent(display, RootWindow(display, DefaultScreen(display)),
+ False, SubstructureNotifyMask | SubstructureRedirectMask, &ce);
+
+ ce.xclient.data.l[0] = 0;
+ XSendEvent(display, RootWindow(display, DefaultScreen(display)),
+ False, SubstructureNotifyMask | SubstructureRedirectMask, &ce);
+
+ while (1) {
+ XNextEvent(display, &report);
+ }
+
+ return 1;
+}