linuxdeploy plugin to extract AppImage icon and set it as the AppImage Icon on XDG supported platforms.

linuxdeploy-plugin-xdg.sh

#!/bin/bash

# ------------------------------------------------------------------------------
# Install:
#  1. Put this script alongside with linuxdeploy or in the PATH
#  2. make it executable (chmod +x linuxdeploy-plugin-xdg)
#
# Usage:
#  1. Set the env variable XDG_ICON to your png icon.
#  2. Call with linuxdeploy
#
# Example:
#  export XDG_ICON=/path/to/my/png/icon
#  linuxdeploy --appdir=[...] -d [...] -i [...] --plugin xdg --output appimage
# ------------------------------------------------------------------------------

# --------------------------------------------------
# linuxdeploy plugin api
# --------------------------------------------------

while [ "$1" != "" ]; do
    PARAM=`printf "%s\n" $1 | awk -F= '{print $1}'`
    VALUE=`printf "%s\n" $1 | sed 's/^[^=]*=//g'`
    if [[ $VALUE == $PARAM ]]; then
        shift
        VALUE=$1
    fi
    # echo "$PARAM = $VALUE"
    case $PARAM in
        --appdir)
            ARG_APP_DIR=$VALUE
            ;;
        --plugin-api-version)
            ARG_PLUGIN_API_VERSION=1
            ;;
	--plugin-type)
            ARG_PLUGIN_TYPE=1
	    ;;
        *)
            echo "[xdg] ERROR: unknown parameter \"$PARAM\""
            usage
            exit 1
            ;;
    esac
    shift
done

if [[ ! -z "$ARG_PLUGIN_API_VERSION" ]]; then
	echo "0"
	exit 0
fi

if [[ ! -z "$ARG_PLUGIN_TYPE" ]]; then
	echo "input"
	exit 0
fi

if [[ -z "$ARG_APP_DIR" ]]; then
	echo "[xdg] --appdir is required"
	exit 1
fi

# --------------------------------------------------
# plugin parameters
# --------------------------------------------------

if [[ -z "$XDG_ICON" ]]; then
	XDG_ICON="$PWD/xdg-icon.png"
fi

echo "[xdg] XDG_ICON=$XDG_ICON"

if [[ ! -f "$XDG_ICON" ]]; then
	echo "[xdg] $XDG_ICON does not exists"
	exit 1
fi

if [[ ! $XDG_ICON == *png ]]; then
    echo "[xdg] xdg icon must be in png format (suggested size: 128x128)"
    exit 1
fi

mkdir -p "$ARG_APP_DIR/apprun-hooks"
HOOK="$ARG_APP_DIR/apprun-hooks/xdg-icon-hook.sh"

echo "[xdg] Deploying xdg icon $XDG_ICON"
cp "$XDG_ICON" "$ARG_APP_DIR/xdg-icon.png"

# --------------------------------------------------
# Hook script
# --------------------------------------------------

echo "[xdg] Deploying xdg-icon-hook.sh"

cat > $HOOK <<- EOM
# Generated by linuxdeploy-plugin-xdg

if [ ! -z "\$APPIMAGE" ] && [ ! -z "\$APPDIR" ]; then

    if [[ -z "\$XDG_CACHE_HOME" ]]; then
        XDG_CACHE_HOME="\$HOME/.cache/thumbnails/normal"
    fi

    if [[ ! -d "\$XDG_CACHE_HOME" ]]; then
        mkdir -p "\$XDG_CACHE_HOME"
    fi

    MD5=\$(echo -n "file://\$APPIMAGE" | md5sum | cut -d' ' -f1)
    cp "\$APPDIR/xdg-icon.png" "\$XDG_CACHE_HOME/\$MD5.png"
    xdg-icon-resource forceupdate 1>/dev/null 2>&1 &

fi

EOM