Add support for aliasing dock icons into sketchybar

[ghost]

It would be really nice if there was some way to mirror dock icons to sketchy bar, or even just app icons themselves

[FelixKratz]

I have played with app icons a while back, but did not come up with a way to include it in the configuration syntax.
Much has changed since then so maybe I will think about it again. It would not be an alias, because it is not dynamic, but could be a special kind of image where images could also take some syntactical abstraction of the application name and display the app icon as the image.

[FelixKratz]

All image properties can now be supplied app.<bundle_identifier> like I have done in this small example which shows the active application icon

app_icons.mp4

sketchybarrc:

sketchybar --add item front_app left                            \
           --set front_app label=Window                         \
                           icon.drawing=on                      \
                           icon.background.drawing=on           \
                           icon.background.color=0x00000000     \
                           icon.background.image.scale=0.5      \
                           script="$PLUGIN_DIR/window_title.sh" \
           --subscribe front_app front_app_switched

window_title.sh:

update() {
  sketchybar --set $NAME label="$INFO" \
                         icon.background.image="app.$(osascript -e "get id of app \"$INFO\"")"
}

case "$SENDER" in
  "front_app_switched") update
  ;;
esac