This explains how to configure multiple keyboards in Sway, and how to
use advanced configuration when regular `xkb_options` are not enough.

## Sway configuration

Luckily, Sway has great support for multiple keyboards with different
layouts, so it nicely adjusts to whatever keyboard you have plugged in
or can use separate configurations for a physical keyboard and the
laptop keyboard.

First, identify the identifiers for the keyboards you have plugged in,
using the following command:

```shell
$ swaymsg -t get_inputs
```

Look for the lines starting with `Identifier:` for the device you're
interested in.

Next, add one section for each of your keyboards to `~/.config/sway/config`:

```text
input "1278:32:PFU_Limited_HHKB-Classic" {
	xkb_layout "us"
	xkb_model "hhk"
	xkb_options "compose:ralt"
	xkb_capslock "disabled"
}

input "1133:49948:Logitech_USB_Keyboard" {
	xkb_file ".xkb/keymap/logitech"
}
```

The example above lists a HHKB ("Happy Hacking") keyboard where right
Alt acts as the Compose key. More options are documented in the man
pages [sway-input(5)](https://manned.org/sway-input.5) as well as
[xkeyboard-config(7)](https://manned.org/xkeyboard-config.7).

In the case where the existing XKB options are not sufficient, you
need to refer to a separate XKB configuration file, as described below.

## XKB configuration

To configure my Logitech keyboard, the plan was to have the key
mapping reasonably close to the HHKB layout.

In my case, I have two files under `~/.xkb` (the directories need to
first be created): This is the `~/.xkb/keymap/logitech` file:

```text
// Derived from `setxkbmap -print`,
// added the "+unixy" part to xkb_symbols.
xkb_keymap {
	xkb_keycodes  { include "evdev+aliases(qwerty)"	};
	xkb_types     { include "complete"	};
	xkb_compat    { include "complete"	};
	xkb_symbols   { include "pc+us+inet(evdev)+unixy"	};
	xkb_geometry  { include "pc(pc105)"	};
};
```

This file is the output from running `setxkbmap -print`, but adds the
`+unixy` part to the `xkb_symbols` section. This refers to the
`~/.xkb/symbols/unixy` file with the following content:

```text
partial alphanumeric_keys
xkb_symbols "unixy" {
	// exchange backspace and backslash
	key <BKSL> {	[ BackSpace, Backspace ] };
	key <BKSP> {	[ backslash, bar ] };

	// caps is ctrl
	key <CAPS> {	[ Control_L ] };
	modifier_map Control { <CAPS> };

	// right alt is compose
	key <RALT> {	[ Multi_key ] };
};
```