Should miral support for changing keymap of running applications

[Pajn]

Setting a new keymap with miral::Keymap::set_keymap only applies to new applications, existing applications still continues to use the old keymap. Surface contains a method set_keymap keymap which I assume can be used for changing the keymap of a running application, but it requires arguments I'm not sure are that easily accessible from outside mir.

Would it make sense to add the method miral::WindowInfo::set_keymap(miral::Keymap keymap) or something like that for changing keymap of running applications?

[AlanGriffiths]

my first thought is that failing to update the keymap of running applications is a bug. @RAOF do you concur?

[RAOF]

I forget whether or not we wanted to support different windows having different keymaps, in which case we would not want miral::Keymap::set_keymap to update the keymaps of all windows.

I think we do want to allow different windows to have different keymaps, so I think that miral::WindowInfo::set_keymap() is a sensible addition. Maybe miral::Keymap::set_keymap should actually be called miral::Keymap::set_default_keymap?

[AlanGriffiths]

I think the keymap controlled by miral::Keymap::set_keymap is the session wide default.

I agree that windows do not have to respect that default, but is that a shell function?

[RAOF]

How else can the shell tell the window which (non-default) keymap it should use?

The shell (or, at least, desktop environment) is in charge of keymaps.

[AlanGriffiths]

After having a poke around, setting "the" keymap applies to mir::common::input, and the seat registers a ConfigObserver. WlKeyboard takes the current keymap from the seat, but subsequent changes are not notified.

[AlanGriffiths]

After having a poke around, setting "the" keymap applies to mir::common::input, and the seat registers a ConfigObserver. WlKeyboard takes the current keymap from the seat, but subsequent changes are not notified.

To clarify: WlSeat::ConfigObserver updates the current keymap on the seat, but does not notify existing WlKeyboards.

It doesn't sound unreasonable to propagate the change to any apps. It isn't clear to me how apps should respond as there are sensible usecases for different apps to use different keymaps.