input_method: send unavailable to the newcomer

[ezemtsov]

Hi!

I'm the author of ewm, an emacs driven compositor which is based on smithay. Lately I was looking into adding generic support for external input methods (in addition to emacs which already works), so that e.g. ewm would start supporting fcitx5 etc. And while testing it I found a bug related to input_method_v2 protocol implementation in smithay.

In ewm, emacs as input method is enabled by default, and its zwp_input_method_v2 object is the seat's tracked instance. When a user starts another program (e.g. fcitx5), it calls get_input_method on the same seat. Currently in add_instance, Smithay emits unavailable on the original instance (emacs) and leaves fcitx5's new object untracked. This breaks the original input method while leaving fcitx5 with no follow up.

Instead, per protocol the compositor should emit unavailable on the new input method (fcitx5), and the original connected input method (emacs) instance stays and keeps receiving activate/deactivate.

Here's an example of a correct behavior in Sway, keeping the existing instance and sending unavailable to the newcomer:

  if (relay->input_method != NULL) {
      sway_log(SWAY_INFO, "Attempted to connect second input method to a seat");
      wlr_input_method_v2_send_unavailable(input_method);
      return;
  }

The protocol original description: here

Checklist

• I agree to smithay's Developer Certificate of Origin.

[Drakulix]

Seems sensible, thanks!