bug#62164: 29.0.60; ediff behaves poorly by default on tiling window managers

[Po Lu via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Po Lu <luangruo@yahoo.com> writes:

> Spencer Baugh <sbaugh@janestreet.com> writes:
>
>> ediff defaults to a multiframe UI on graphical displays.  If the user is
>> running a tiling window manager on X, the control panel frame gets tiled
>> and the whole thing becomes either very ugly or unusable.
>>
>> This is a very long-standing bug, but it should be fixed.  Most tiling
>> window manager users work around this with:
>>
>> (setq ediff-window-setup-function 'ediff-setup-windows-plain)
>>
>> But I would rather the multiframe UI just work correctly by default.
>
> Maybe such users could be taught to make the utility window
> override-redirect instead.
>
>> On X, perhaps we should set _NET_WM_WINDOW_TYPE to
>> _NET_WM_WINDOW_TYPE_UTILITY for the ediff control panel frame, so that
>> tiling window managers float the control panel frame frame by default.
>> This would probably need to be a new frame parameter specific to X.  I
>> can try to make that change if that seems reasonable.  (This would also
>> be useful for allowing other packages to have multiframe UI modes.)
>
> The ediff control frame is not a utility frame because you are supposed
> to type in it.
>
> One window manager which extensively uses keyboard navigation (I'm not
> sure I remember which) applies the No Input focus model to
> _NET_WM_WINDOW_TYPE_UTILITY, not letting you type in such toplevel
> windows.
>
>> I'm not sure what we'd do for other windowing systems.  Probably the
>> only other platform where tiling window managers are at all common is
>> Wayland; perhaps there's some way to set this hint through PGTK?
>
> No, Wayland doesn't provide any of this, unless you use a protocol that
> is exclusive to GNOME Shell.  Popups are instead supposed to be
> implemented as xdg_popup windows and not xdg_toplevels, or toplevels
> transient for another toplevel.  The former is technically infeasible
> under GTK, and the latter results in the control frame obscuring
> everything else.

BTW, `x-change-window-property' lets you mess around with window
properties if you want.  No frame parameter needed.