How to get inner and outer window dimensions with Xlib/XCB? - xlib

Question

Is there a reliable way to get the inner and outer rectangle of a top
level window with XCB/Xlib? (IOW frame and client rectangle).
Here's what I tried:
xcb_get_geometry always returns the initial dimensions even after
the window gets resized (what gives?)
I figured I would call xcb_query_tree repeatedly until I find the
window's frame window - is this the way to do it? I figure ICCCM/EWMH
should provide this but couldn't find anything. Is there any other
standard/non-standard for this? Anyway that doesn't work with
compiz/ubuntu10 because xcb_query_tree reports the client window as
having root = parent (under normal ubuntu wm the window gets properly
reparented).
xcb_translate_coordinates() seemed to be the only reliable way to
get root-based coords[1] in 2007 -- is this still the case? I.e. is
XCB_CONFIGURE_NOTIFY non-standard with WMs?
[1] http://fixunix.com/xwindows/91652-finding-position-top-level-windows.html

Answer 1

This is a partial answer as it only explains how to find the inner dimensions of a window. Also I am not sure if this is the canonical way to go but it works for me.
You can subscribe to the XCB_EVENT_MASK_RESIZE_REDIRECT event when creating a window:
xcb_window_t window = xcb_generate_id (connection);
const xcb_setup_t *setup = xcb_get_setup (connection);
xcb_screen_t *screen = xcb_setup_roots_iterator (setup).data;
uint32_t mask = XCB_CW_EVENT_MASK;
uint32_t valwin[1] = { XCB_EVENT_MASK_EXPOSURE
| XCB_EVENT_MASK_RESIZE_REDIRECT };
xcb_create_window(
connection,
XCB_COPY_FROM_PARENT,
window,
screen->root,
0, 0,
800, 600,
0,
XCB_WINDOW_CLASS_INPUT_OUTPUT,
screen->root_visual,
mask, valwin);
xcb_map_window(connection, window);
xcb_flush(connection);
In the event loop you can then keep track of resizes:
xcb_generic_event_t *event;
uint16_t width = 0, height = 0;
while ((event = xcb_wait_for_event(connection)) != NULL) {
switch (event->response_type & ~0x80) {
case XCB_EXPOSE: {
/* ... */
break;
}
case XCB_RESIZE_REQUEST: {
auto resize = (xcb_resize_request_event_t*) event;
if (resize->width > 0) width = resize->width;
if (resize->height > 0) height = resize->height;
break;
}
default:
break;
}
free(event);
xcb_flush(connection);
}
Note that I am not sure whether this event is emitted when you initiate the resize from your application code using xcb_configure_window for example. I never tested it and just update the width and height in a wrapper function for xcb_configure_window.