#!/bin/sh

# Sets the correct DPI for your monitor instead of the generic '100'
# ! Make sure there is no DPI entry in your Xresources already!

FILE=$XDG_CONFIG_HOME/X11/xresources

grep 'Xft.dpi' "$FILE" && xrdb -merge "$FILE" && exit

INFO=/tmp/display_info
xrandr | grep ' connected' > $INFO

WIDTH_MM=$(awk '{print $NF}' $INFO)
WIDTH_IN=$(echo "${WIDTH_MM%mm}" | awk '{print $1 * 0.03937007874015748}')

HEIGHT_MM=$(awk '{print $(NF-2)}' $INFO)
HEIGHT_IN=$(echo "${HEIGHT_MM%mm}" | awk '{print $1 * 0.03937007874015748}')

DIAGONAL_IN=$(awk -v w="$WIDTH_IN" -v h="$HEIGHT_IN" \
   'BEGIN{print sqrt(w^2 + h^2)}')

PX=$(cut -d ' ' -f 4 $INFO)

WIDTH_PX=${PX%x*}

TEMP_HEIGHT_PX=${PX#*x}
HEIGHT_PX=${TEMP_HEIGHT_PX%%+*}

DIAGONAL_PX=$(awk -v w="$WIDTH_PX" -v h="$HEIGHT_PX" \
   'BEGIN{print sqrt(w^2 +h^2)}')

DPI=$(awk -v dp="$DIAGONAL_PX" -v di="$DIAGONAL_IN" \
   'BEGIN{print dp / di}')

echo "Xft.dpi: $DPI" >> "$FILE"
xrdb -merge "$FILE"
rm $INFO