Automatically hide polybar if necessary

xfreerdp doesn’t seem to play nice with Polybar, so hide Polybar whenever
xfreerdp is focused.

polybar/.config/herbstluftwm/autostart.d/polybar.sh

@@ -1,2 +1,2 @@
 #!/usr/bin/env bash
-pgrep polybar || { polybar "$(hostname)" 2> /dev/null & }
+pgrep polybar || { autohide-polybar.sh && polybar "$(hostname)" 2> /dev/null & }

polybar/usr/bin/autohide-polybar.sh

@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+
+# Has to start with my_ or herbstluftwm will throw up.
+attr_name=my_polybar_showing
+
+herbstclient get_attr "$attr_name" 1> /dev/null 2>&1 \
+    || herbstclient new_attr bool "$attr_name"
+herbstclient set_attr "$attr_name" true
+
+herbstclient -i focus_changed | while read -r _ winid _; do
+    window_class=$(herbstclient attr "clients.${winid}.class")
+    showing_polybar=$(herbstclient attr "$attr_name")
+
+    if [[ $window_class =~ xfreerdp ]]; then
+        polybar-msg cmd hide > /dev/null \
+            && herbstclient set_attr "$attr_name" false
+    elif [[ $showing_polybar == "false" ]]; then
+        polybar-msg cmd show > /dev/null \
+            && herbstclient set_attr "$attr_name" true
+    fi
+done &