xcb_poll_for_event does not detect XCB_CLIENT_MESSAGE event for closing window - c++

Question

I am porting my application to Linux, and I am using the XCB library for window handling. I need to detect when the window closes, so that the application can exit. However, the system cannot block on the main window loop due to the way the system is designed. This is easy in Windows, since you just use PeekMessage. However, xcb does not seem to work when I try to detect XCB_CLIENT_MESSAGE using xcb_poll_for_event. The close button on the window in fact has no functionality when I try to inject the WM_DELETE_WINDOW protocol.
Window setup:
// initialize XCB
this->connection = xcb_connect(NULL, NULL);
this->screen = xcb_setup_roots_iterator(xcb_get_setup(this->connection)).data;;
// create window
u32 mask = 0;
u32 values[1];
this->window = xcb_generate_id(this->connection);
mask = XCB_CW_EVENT_MASK;
values[0] = XCB_EVENT_MASK_EXPOSURE;
xcb_create_window(this->connection, 0, this->window, this->screen->root, 0, 0, width, height, 0, XCB_WINDOW_CLASS_INPUT_OUTPUT, this->screen->root_visual, mask, values);
// setup close handler event
xcb_intern_atom_cookie_t protocolCookie = xcb_intern_atom_unchecked(this->connection, 1, 12, "WM_PROTOCOLS");
xcb_intern_atom_reply_t* protocolReply = xcb_intern_atom_reply(this->connection, protocolCookie, 0);
xcb_intern_atom_cookie_t closeCookie = xcb_intern_atom_unchecked(this->connection, 0, 16, "WM_DELETE_WINDOW");
this->m_closeReply = xcb_intern_atom_reply(this->connection, closeCookie, 0);
xcb_change_property(this->connection, XCB_PROP_MODE_REPLACE, this->window, protocolReply->atom, 4, 32, 1, &(this->m_closeReply->atom));
free(protocolReply);
// map and flush
xcb_map_window(this->connection, this->window);
xcb_flush(this->connection);
Message loop:
// handle all incoming messages
xcb_generic_event_t* e;
while(e = xcb_poll_for_event(connection))
{
// take action from message
switch(e->response_type & ~0x80)
{
case XCB_EXPOSE:
// invalidated
xcb_flush(connection);
break;
case XCB_CLIENT_MESSAGE:
// close window
if(((xcb_client_message_event_t*)e)->data.data32[0] == (*this->m_closeReply).atom)
return false;
break;
}
// cleanup
free(e);
}
Window closing works flawlessly when I replace xcb_poll_for_event with xcb_wait_for_event, but then the window loop is blocked on waiting for messages. I just need to know what I am doing wrong for the event to never get detected when using xcb_poll_for_event.