Index: x11.c
===================================================================
RCS file: /sources/qemacs/qemacs/x11.c,v
retrieving revision 1.29
diff -u -r1.29 x11.c
--- x11.c	17 Dec 2013 16:06:36 -0000	1.29
+++ x11.c	7 Jan 2014 00:14:31 -0000
@@ -55,6 +55,7 @@
 static Display *display;
 static int xscreen;
 static Window window;
+static Atom wm_delete_window;
 static GC gc, gc_pixmap;
 static XWindowAttributes attr;
 static int event_mask;
@@ -319,6 +320,9 @@
                     XNFocusWindow, window,
                     NULL);
 
+    wm_delete_window = XInternAtom (display, "WM_DELETE_WINDOW", False);
+    XSetWMProtocols (display, window, &wm_delete_window, 1);
+
     gc = XCreateGC(display, window, 0, NULL);
 #ifdef CONFIG_XFT
     renderDraw = XftDrawCreate(display, window, attr.visual,
@@ -1247,6 +1251,22 @@
     while (XPending(display)) {
         XNextEvent(display, &xev);
         switch (xev.type) {
+        case ClientMessage:
+            if ((Atom)xev.xclient.data.l[0] == wm_delete_window) {
+                // cancel pending operation
+                ev->key_event.type = QE_KEY_EVENT;
+                ev->key_event.key = KEY_CTRL('g');
+                qe_handle_event(ev);
+
+                // simulate C-x C-c
+                ev->key_event.type = QE_KEY_EVENT;
+                ev->key_event.key = KEY_CTRL('x');
+                qe_handle_event(ev);
+                ev->key_event.type = QE_KEY_EVENT;
+                ev->key_event.key = KEY_CTRL('c');
+                qe_handle_event(ev);
+            }
+            break;
         case ConfigureNotify:
             if (term_resize(s, xev.xconfigure.width, xev.xconfigure.height)) {
                 qe_expose_set(s, rgn, 0, 0, s->width, s->height);