[LightDM] On keyboard layouts

[Robert Ancell]

On 7 February 2014 12:49, Christian Seiler <christian at iwakd.de> wrote:

>
>
> 1. All greeters I've looked at (Gtk, unmaintained Qt, KDE, Razor-QT,
> Unity) don't seem to implement this at all... Ok, the Qt-based greeters
> are no surprise. But for Gtk/Unity: I see some references to old bug
> reports online if I search for this, but they reference C code, whereas
> the Unity greeter is now written completely in Vala. (At least current
> bzr trunk.) And ok, Vala is compiled to C, but the Vala code I looked
> at contains nothing that I could find that contains anything resembling
> keyboard layouts.
>
> Am I missing something here? Currently, it appears to me that nobody is
> actually using that code. Nevertheless, I've seen screenshots of the
> Unity greeter with a keyboard symbol, is that perhaps an old version?
>

Unity Greeter uses the keyboard indicator which does the keyboard
management, so the rest of the greeter GUI doesn't need any knowledge of
keyboard layouts. At the time I was adding keyboard support it wasn't clear
we would use the same indicator code as the session but in the end we did
(as well as using gnome-settings-daemon which manages some keyboard
settings).


>
> 2. I get a huge list of layouts from the backend, it appears to me that
> those are all layouts that are installed on my system. (472 entries) If
> I want to use that for writing some kind of layout switcher for a
> greeter, I don't see how that could be made usable in a reasonable way.
> The only greeter outside of lightdm of which I know that it supports
> layouts is gdm3, and that uses the current XkbLayouts X setting to
> restrict the available layouts to those, making it much easier for a
> system administrator to choose a sane policy of available layouts.
>

I think it depends on how XKB is configured. In my case I only get a few
back. I have had a little look at the XKB protocol and it is quite insanely
complicated so no surprises it might vary wildly in configuration.

However, in the case of GNOME (and by extension Ubuntu) they've moved to
using gnome-settings-daemon to switch between keyboard layout / input
method combinations. I am not sure if this will become a standard across
desktops.

My thoughts on where we go from here:
- It seems desirable that liblightdm should provide basic support for
things that a greeter could need like keyboard support. This functionality
will be optional if a greeter wants to use something more complex /
appropriate.
- We should attempt to transparently support whatever technologies are
being used (e.g. Wayland, IBus, etc).
- My knowledge of the keyboard system is quite low so anyone who wants to
step in and own this part of LightDM is welcome to do so.

Thanks,
--Robert
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