Add picom inactive window opacity automatic toggle

Whenever i3 is using gapless mode, all windows will be opaque. When gaps
are shown inactive windows will have some transparency and blur behind
them.

Script can be invoked manually with `picom_toggle_inactive_opacity` to
toggle, `picom_toggle_inactive_opacity on` or
`picom_toggle_inactive_opacity off` to set it respectively.

.local/bin/picom_toggle_inactive_opacity

@@ -0,0 +1,27 @@
+#!/bin/bash
+# toggle the translucency of inactive windows in the picom compositor
+# by substituting the true/false setting in the picom config file.
+# picom will automatically reload its settings on any config file changes.
+#
+# scipt can be called without arguments to toggle the value;
+# or with on / off to set it to translucent / opaque, respectively.
+
+piconf="$XDG_CONFIG_HOME"/picom/picom.conf
+
+line=$(grep -n "inactive-opacity-override" "$piconf")
+
+IFS=: read -r line text < <(grep -n "inactive-opacity-override" "$piconf")
+
+_replace() { # line file old new
+  sed -i "$1 s/$3/$4/" "$2"
+}
+
+if [ "$1" = "off" ]; then
+  _replace "$line" "$piconf" "true" "false"
+elif [ "$1" = "on" ]; then
+  _replace "$line" "$piconf" "false" "true"
+elif echo "$text" | grep -q "true"; then
+  _replace "$line" "$piconf" "true" "false"
+elif echo "$text" | grep -q "false"; then
+  _replace "$line" "$piconf" "false" "true"
+fi