added check for other windowmanagers

src/main.scm

@@ -5,6 +5,16 @@
   (let ((dpy (open-display)))
     (synchronize dpy #t)
     (init-sync-x-events dpy)
+    ;; first try if there is already a window-manager
+    (with-handler
+     (lambda (condition punt)
+       (mdisplay "Another window manager is already running on this screen\nTerminate it before running Orion.\n")
+       (exit))
+     (lambda ()
+       (display-select-input dpy (default-root-window dpy)
+			     (event-mask substructure-redirect))
+       (display-sync dpy #f)))
+
     ;; for debugging:
 ;    (spawn (lambda ()
 ;	     (let loop ((se (most-recent-sync-x-event)))