Fix key group

[andremarcais]

Fixes/Closes #115

Description

• Displays effective key group.
• Re-displays on xkb state change.

Release notes

Notes: Bug fix for effective key group display.

[andremarcais]

As of now there is no mutex on the layout_text global (nor is there on any of the globals like unlock_state and modifier_string) which is potentially a problem for --redraw-thread.

[Raymo111]

@andremarcais what exactly is a key group? I just want to be certain before merging this.

[andremarcais]

In X, one of four key groups is active. X maps a keycode (which represents a physical key) and group to a character.

In higher level user configuration the user may, e.g., set the layout to us,fr, which causes Group 1 to be mapped to us characters and Group 2 to be mapped to fr characters. The active group determines what character results from a keycode.

Using options like grp:shifts_toggle makes switching the active group easy.

My explanation oversimplifies this a little bit. This page explains this in greater detail.

[Raymo111]

I see. Alright, I'll merge the PR.

[Raymo111]

Approved based on working screencap and good feedback from other users.