Initial layer-indicator support

[twadzins]

Pointer to discord thread: https://discord.com/channels/877392805654306816/1221190895806709911

This code does the following:

• Updates the dtsi erb to create behaviors and macros which are variants of the thumb, space and thumb_parang behaviors and associated macros that will, if enabled, send a unique modifier sequence when a layer key is pressed, and send F18 when the layer key is released. These behaviors are then applied to keymap.json in place of the current &thumb, &space and &thumb_parang custom mappings. The functionality is enabled with a flag USE_LAYER_INDICATORS, which is disabled by default
• Adds to the rake build: Create a BetterTouchTool preset that displays an overlay of the active keyboard layer. This preset building uses the unique key sequences sends by the above change to the dtsi

[sunaku]

Thanks for contributing this! ️❤️ I will review it when I get some time. 🧗 In the meantime, it would be helpful to get more users from the community to help test it and provide feedback. Also, I would like to expand this to support all 3 OS'es in the future.

[sunaku]

Hey @twadzins, I've updated this patch to the latest v38 release and did some minor additional refactoring in my branch: https://github.com/sunaku/glove80-keymaps/tree/layer-indicator

Would it be possible to bundle the layer map diagrams into the ZIP file for offline usage? Currently the preset appears to load them from GitHub, which requires an internet connection.

[buzz]

This is exactly what I've been looking for. 👍

Regarding extending this to Linux: sxhkd might not be a good choice. It only runs under X11, no Wayland support.

For Wayland this is more complicated as Wayland's security model doesn't allow this. On Wayland the compositor would need to support this. So, one needs separate solutions for each Desktop Environment.

Another way of doing this would be to run a tiny daemon that acts lower level (evdev?) that is before key strokes even reach the display manager. This way, it works on both Wayland and X11.

Some input remapping tools do it this way. I couldn't find one that allows running arbitrary commands though...

So maybe one could write a tiny daemon that reacts to those key presses and sends events through DBus to a desktop client.

Starting points:

• https://docs.rs/evdev/latest/evdev/
• https://python-evdev.readthedocs.io/en/latest/