WM_HINTS such as SKIP_TASKBAR not always respected?

[AlbinoGeek]

Guake should never be in the taskbar, due to its window class hints, but it gets in there somehow. I also write a number of conky applications that have window classes that result in their exclusion in Gnome, but not in fynedesk.

In Gnome on X you can use xprop to query these hints.

I have windows with various hints, SKIP_PAGER, SKIP_TASKBAR, ABOVE, STICKY, etc--

$ xprop | grep -i ABOVE
(click on a window)
_NET_WM_STATE(ATOM) = _NET_WM_STATE_SKIP_PAGER, _NET_WM_STATE_SKIP_TASKBAR, _NET_WM_STATE_FULLSCREEN, _NET_WM_STATE_ABOVE, _NET_WM_STATE_STICKY, _NET_WM_STATE_FOCUSED
NET_WM_ALLOWED_ACTIONS(ATOM) = _NET_WM_ACTION_FULLSCREEN, _NET_WM_ACTION_CHANGE_DESKTOP, _NET_WM_ACTION_CLOSE, _NET_WM_ACTION_ABOVE, _NET_WM_ACTION_BELOW

I tried to find the same hints in Gnome's Looking Glass, but could not find the relevant property.

global.get_window_actors()[0].get_meta_window().<something here, idk>

In Gnome, DESKTOP, ABOVE and STICKY, or SKIP_TASKBAR cause the window to be removed in the shell's window list.

SKIP_PAGER, or DESKTOP, or ABOVE and STICKY cause the window to be removed from the ALT+TAB list.

Originally posted by @AlbinoGeek in https://github.com/fyne-io/fynedesk/issues/106#issuecomment-789169742