shell(bin): add is-system-theme-light

.config/shell/bin/is-system-theme-light

@@ -0,0 +1,41 @@
+#!/bin/bash
+# Checks the system light/dark theme status
+# Returns 0 (true) if the theme is light, 1 (false) if the theme is dark
+
+set -e
+
+declare -- method theme
+
+# Figure out what environment we're in, so we can use the correct detection method
+if [ -n "$SSH_TTY" ]; then
+   method=ssh
+elif [ -n "$KDE_SESSION_UID" ]; then
+   method=kde
+else
+   method=unknown
+fi
+
+set -u
+
+config_dir="${XDG_CONFIG_HOME:-"$HOME"/.config}"
+
+case "$method" in
+   (ssh) theme=dark;;
+   (kde)
+      if grep -Fq dark "$config_dir/kdeglobals"; then
+         theme=dark
+      else
+         theme=light
+      fi
+      ;;
+   (unknown|*)
+      # assume dark theme
+      theme=dark
+      ;;
+esac
+
+if [ "$theme" = light ]; then
+   exit 0
+else
+   exit 1
+fi