HOWTO: Use polytonic Greek in Slackware

I’ve been using polytonic Greek in a few of my earlier essays at the University, mostly to either correctly determine which term of Aristotle’s I’m hinting at, but also in relation to modern German philosophy (both Hegel and Heidegger refer to Platon and Aristoteles for instance). I set this up on my laptop that’s running Fedora core 17, but I forgot how I did it.

Consequently, I haven’t dared to update it, from the Fear of Fedora upgrades as well as losing my ability to write polytonically (not even sure if that’s a word).

Here’s how I set it up on my Slackware 14.1 x86_64 installation that runs Xfce & i3 DE:
# Check that you have the keymap you want installed already:
$ ls /usr/share/kbd/keymaps/i386/qwerty/

# I want to use 'no' (Norwegian) and 'gr' with the polytonic variant
# the variants are listed inside the keymap. To confirm, you can do:
$ less /usr/share/kbd/keymaps/i386/qwerty/gr.map.gz

# The command to activate the changed layout settings that switches
# between 'no' and 'gr' with polytonic variant using Left Alt+Left Shift:
$ setxkbmap -option grp:alt_shift_toggle no,gr -variant ',polytonic' -display 0:0

# Confirm current settings:
$ setxkbmap -query

# Optional: install font (download below)
su -c 'cp newathu405.ttf /usr/share/fonts/TTF/'

You might also need a capable font, like this one, but I like Times New Roman.
That was it, really! I can now swap back and forth between the two as easily as I could on my Fedora box!