I've changed the property as you specified, however it seems the event isn't being sent. Here is my code: #include <stdio.h> #include <stdint.h> #include <xcb/xcb.h> int main() { xcb_connection_t* c = xcb_connect(0, 0); xcb_screen_t* s = xcb_setup_roots_iterator(xcb_get_setup(c)).data; xcb_window_t w = xcb_generate_id(c); const uint32_t values = XCB_EVENT_MASK_EXPOSURE; xcb_create_window(c, 0, w, (*s).root, 0, 0, 128, 128, 0, XCB_WINDOW_CLASS_INPUT_OUTPUT, (*s).root_visual, XCB_CW_EVENT_MASK, &values); xcb_intern_atom_cookie_t cookie = xcb_intern_atom(c, 1, 12, "WM_PROTOCOLS"); xcb_intern_atom_reply_t* reply = xcb_intern_atom_reply(c, cookie, 0); xcb_change_property(c, XCB_PROP_MODE_REPLACE, w, (*reply).atom, 4, 32, 1, "WM_DELETE_WINDOW"); xcb_map_window(c, w); xcb_flush(c); xcb_generic_event_t* event; while((event = xcb_wait_for_event(c))) { puts("Event occurred"); switch((*event).response_type & ~0x80) { case XCB_EXPOSE: puts("Expose"); break; } } return 0; } It should output "Event occurred" when any event occurs, and it does for Expose events, but not when I close out of the window. Any suggestions? <div class="gmail_quote">On Fri, Dec 31, 2010 at 5:55 AM, Vincent Torri <<a href="mailto:vtorri@univ-evry.fr">vtorri@univ-evry.fr</a>> wrote: <blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"> <div class="im"> On Fri, 31 Dec 2010, Cinolt wrote: </div><div class="im"><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"> Hello, I'm assuming that I need to call xcb_change_property on my window to change one of its properties. What should I set the type argument to, and am I correct in assuming that the data argument should be "WM_DELETE_WINDOW"? xcb_void_cookie_t xcb_change_property (xcb_connection_t *c, /* Connection to the X server */ uint8_t mode, /* Property mode */ xcb_window_t window, /* Window */ xcb_atom_t property, /* Property to change */ xcb_atom_t type, /* Type of the property */ uint8_t format, /* Format of the property (8, 16, 32) */ uint32_t data_len, /* Length of the data parameter */ const void *data); /* Data */ </blockquote> </div> I give you the way to find it by yourself if later you need to use ICCCM or EWMH again). In the link i gave you [1], it is a subsection of the ClientMessage events [2]. It is said that the window you want to delete should have the WM_PROTOCOLS property, with the atom WM_DELETE_WINDOW and that is it related to the ClientMessage event (see section 4.1.2.7) [3]. So you need to change the property of your window. And indeed, you use xcb_change_property() to do that:<div class="im"> xcb_void_cookie_t xcb_change_property( </div> xcb_connection_t *c, /* Connection */<div class="im"> uint8_t mode, /* Property mode */ xcb_window_t window, /* Window */ xcb_atom_t property, /* Property to change */ xcb_atom_t type, /* Type of the property */ uint8_t format, /* Format of the property (8, 16, 32) */ uint32_t data_len, /* Length of the data parameter */ const void *data); /* Data */ </div> * the parameters c and window are trivial. * mode: what you do with that property (replacing a value, append or prepend it). Replace it by passing XCB_PROP_MODE_REPLACE * property: create an atom with the "WM_PROTOCOLS" string (see xcb_inter_atom* functions) * type: the type of the property WM_PROTOCOLS is an atom (first ine of [3], so create an atom with the "ATOM" string (or use the value 4 for the parameter 'type' as it is a predefined value). * format: as [2] mentions, it is 32 * data is an array of the atoms you want to set for the WM_PROTOCOLS property. Here, it is just one atom: the WM_DELETE_WINDOW one (create it with "WM_DELETE_WINDOW") * data_len is the length of the above array, so pass just 1. Note that you can pass several atoms and not just only one: see [3] or [4]. So now, when that window is deleted by clicking on the cross of the titlebar, you'll get a ClientMessage event in your event loop. See [2] to know what to do with that event. Vincent<div class="im"> [1] <a href="http://tronche.com/gui/x/icccm/sec-4.html#s-4.2.8.1" target="_blank">http://tronche.com/gui/x/icccm/sec-4.html#s-4.2.8.1</a> </div> [2] <a href="http://tronche.com/gui/x/icccm/sec-4.html#s-4.2.8" target="_blank">http://tronche.com/gui/x/icccm/sec-4.html#s-4.2.8</a> [3] <a href="http://tronche.com/gui/x/icccm/sec-4.html#s-4.1.2.7" target="_blank">http://tronche.com/gui/x/icccm/sec-4.html#s-4.1.2.7</a> [4] <a href="http://standards.freedesktop.org/wm-spec/wm-spec-1.3.html#id2507897" target="_blank">http://standards.freedesktop.org/wm-spec/wm-spec-1.3.html#id2507897</a> </blockquote></div>