query certain useful terminal attributes

query

#!/bin/bash

printf %b%.b \
        '\e7'               'save cursor position' \
        '\e[9999;9999H'     'move to bottom right' \
        '\e[6n'             'get cursor position'  \
        '\e8'               'restore cursor'       \
        '\e[?u'             'kitty kbd proto'      \
        '\e[?2026$p'        'synchronised output'  \
        '\e[m'              'reset colours'        \
        '\e[38;5;123m'      '256 colour fg'        \
        '\e[38;2;45;67;89m' 'truecolor fg'         \
        '\eP$qm\x1b\\'      'decrqm'               \
        '\e[c'              'da1'                  \
        '\e[m'              'reset colours again'

read -rsdc
IFS=$'\e[;'
size=(${REPLY%%R*})
LINES=${size[2]} COLUMNS=${size[3]}

! [[ $REPLY = *u* ]]; kitty=$?
! [[ $REPLY = *'2026;2'* ]]; sync=$?

# for some reason some terminals (xterm, ghostty, vte-based ones) reply 38:2:: even if they don't support any extra fields
# contour just replies 382456789;49m which is honestly fucked up
! [[ $COLORTERM = *@(24bit|truecolor)* || $REPLY = *38*2*45*67*89*m* ]]; truecolor=$?

if [[ $DISPLAY ]]; then
    IFS=' ' read -r _ _ _ _ self _ < <(xprop -root _NET_ACTIVE_WINDOW)
    # most terminals also set an instance-specific wm class, but rio doesn't, so use the generic one
    IFS='"' read -r _ _ _ class _ < <(xprop -id "$self" WM_CLASS)
else
    class=unknown
fi

tf=(false true)
gb=(bad good)

info () { printf '%s: \e[38;5;51m%s\e[m\e[K\n' "$@"; }
good () { printf '%s: \e[38;5;46m%s\e[m\e[K\n' "$@"; }
bad  () { printf '%s: \e[38;5;196m%s\e[m\e[K\n' "$@"; }

info '$TERM' "$TERM"
info 'wm class' "$class"
info 'size' "${COLUMNS}x$LINES"
info '$COLORTERM' "$COLORTERM"
info 'raw reply' "${REPLY@Q}"
"${gb[kitty]}" 'kitty keyboard proto support' "${tf[kitty]}"
"${gb[sync]}" 'synchronised output support' "${tf[sync]}"
"${gb[truecolor]}" '24bit colour support' "${tf[truecolor]}"

#      r      |     g     |     b     | rdx | gdx | bdx
# ------------+-----------+-----------+-----+-----+----
# max         | 0->max    | 0         |  0  |  1  |  0
# max->0      |    max    | 0         | -1  |  0  |  0
#      0      |    max    | 0->max    |  0  |  0  |  1
#      0      |    max->0 |    max    |  0  | -1  |  0
#      0->max |         0 |    max    |  1  |  0  |  0
#         max |         0 |    max->0 |  0  |  0  | -1

# walk around an rgb cube on the edges that don't include black or white
walkcube () {
    local max=$(($1-1)) fmt=$2
    local rdx=4 gdx=2 bdx=0
    local r=max g=0 b=0
    local i j

    for (( i = 0; i < 6; i++ )) do
        for (( j = 0; j < max; j++ )) do
            printf -v 'hues[i*max+j]' "$fmt" \
                "$(( r += (rdx%6==2)-(rdx%6==5) ))" \
                "$(( g += (gdx%6==2)-(gdx%6==5) ))" \
                "$(( b += (bdx%6==2)-(bdx%6==5) ))"
        done
        (( rdx = (rdx+1) % 6, gdx = (gdx+1) % 6, bdx = (bdx+1) % 6 ))
    done
}

declare -ai hues
walkcube 6 '16 + %d*6*6 + %d*6 + %d'

printf '\e[38;5;%s;48;5;%sm▌' "${hues[@]}"
printf '\e[m 256 colour test\n'

unset hues
walkcube 256 '%d;%d;%d'

h=${#hues[@]}
for (( i = 0; i < h; i++ )) do
    (( i % (h/COLUMNS) )) && unset 'hues[i]'
done

printf '\e[38;2;%s;48;2;%sm▌' "${hues[@]}"
printf '\e[m 24bit colour test\n'