This proof of concept is in an unpolished state, but turned out to be so useful in day-to-day usage that I'm publishing it regardless.

The Problem

In short: EXWM's simulation keys can remap an X application's keybindings, so that it is possible to, for example, control Firefox using vi-like keybindings, purely through the window manager and without resorting to any add-ons.

One unfortunate drawback compared to browser add-ons, however, is that state internal to applications is invisible to EXWM: with the cursor in the address bar or in a web page's text field, one would expect input to show up verbatim, but for that, one has to switch from line-mode (i.e., simulation keys) to char-mode manually! It's easy to imagine (and experience!) that forgetting about toggling input modes wreaks havoc on a browsing session.

The Solution

This program (ab)uses GTK's input method mechanism, which is normally used to open an on-screen keyboard when text is about to be entered anywhere in a GTK application, and to close it afterwards. Here, instead, emacs-client is called to toggle char-mode for the appropriate window. Now it is hardly ever necessary to toggle input modes manually!

Usage

1. Make sure that an Emacs server runs by executing the server-start command in your EXWM session.

2. Build this project with make and start Firefox (or any other GTK 3 application of your choice) so that it uses the new input method module, adapt the path as necessary:

GTK_IM_MODULE_FILE=$HOME/autocharmode/immodules.cache GTK_IM_MODULE=autocharmode firefox

3. Confirm that the input mode toggles automatically, for example by selecting the address bar.