Pick default theme based on terminal background color

[walles]

According to https://stackoverflow.com/a/7767891/473672 some terminals support querying the actual background color of the terminal window.

Unclear what happens with background images / transparency, but still.

Example usage, text after the second $ is the response from the terminal.

~ $ printf "\e]11;?\a"
~ $ ]11;rgb:fefe/f4f4/9c9c

[walles]

Example shell script for querying the terminal background color:

#!/bin/sh

OLDSTTY=$(stty -g)

stty raw -echo min 0
echo "\033]11;?\033\\"

# If this delay is too short you will miss your terminal's response
sleep 1

read -r ANSWER
stty "$OLDSTTY"

# Extract response body
RGB=$(echo "$ANSWER" | sed 's/[^r]*//' | sed 's@[^rgb:0-9a-f/]@@g')
echo "$RGB"

Example response: rgb:fefe/f4f4/9c9c

Inspired by: https://stackoverflow.com/a/30540928/473672

[walles]

We should re-apply ed49174 (pick status bar color based on the current style) or something to that effect after this is done.

[walles]

Done: https://github.com/walles/moar/releases/tag/v1.23.0