#!/bin/bash

new_dirs=
while read -r install_path
do
    share_path=$install_path/exports/share
    case ":$XDG_DATA_DIRS:" in
        *":$share_path:"*) :;;
        *":$share_path/:"*) :;;
        *) new_dirs=${new_dirs:+${new_dirs}:}$share_path;;
    esac
done < <(echo "${XDG_DATA_HOME:-"$HOME/.local/share"}/flatpak"; flatpak  --installations)

XDG_DATA_DIRS="${new_dirs:+${new_dirs}:}${XDG_DATA_DIRS:-/usr/local/share:/usr/share}"
echo "XDG_DATA_DIRS=$XDG_DATA_DIRS"