allowed window operations

[Havoc Pennington <hp redhat com>]

Hi,

Tasklists and pagers need some way to properly activate/deactivate the
menu items for window operations. For example, if I open the window
menu for a dialog, the "Maximize" option might be grayed out for WMs
that don't put a maximize control on dialogs.

However there is no way to know what policy a window manager has
decided on for whether a given operation applies to a given window.
This policy might be computed from semantic type, WM_PROTOCOLS, the
Motif hints, current context, or whatever.

I would suggest a simple hint _NET_WM_ALLOWED_STATE which contains a
list of _NET_WM_STATE atoms that may be toggled. The flaw in this is
that it doesn't cover two operations, minimization and deletion.

We could introduce _NET_WM_STATE_MINIMIZED and _NET_WM_STATE_CLOSED
and use them only in _NET_WM_ALLOWED_STATE, not in _NET_WM_STATE, 
but that seems a bit hacky.

Havoc