- changed error signalling from raising an error to returning #f in

some functions.

scheme/xlib/client.scm

@@ -109,7 +109,8 @@
   "scx_Set_Text_Property")
 
 ;; get-wm-protocols function returns the list of atoms stored in the
-;; WM_PROTOCOLS property on the specified window. These atoms describe
+;; WM_PROTOCOLS property on the specified window, or #f if this
+;; property does not exist or has a bas format. These atoms describe
 ;; window manager protocols in which the owner of this window is
 ;; willing to participate. See XGetWMProtocols.
 
@@ -119,7 +120,7 @@
     (if res
 	(map make-atom
 	     (vector->list res))
-	(error "cannot get WM protocols"))))
+	#f)))
 
 (import-lambda-definition %wm-protocols (Xdisplay Xwindow)
   "scx_Wm_Protocols")
@@ -133,20 +134,17 @@
 				 (list->vector (map atom-Xatom protocols)))))
     (if res
 	res
-	(error "cannot set WM protocols" protocols))))
+	(error "cannot set WM protocols" window protocols))))
 
 (import-lambda-definition %set-wm-protocols! (Xdisplay Xwindow protocols)
   "scx_Set_Wm_Protocols")
 
-;; get-wm-class returns the class hint for the specified window. See
-;; XGetClassHint.
+;; get-wm-class returns the class hint for the specified window or #f
+;; if it does not exists or has a bad format. See XGetClassHint.
 
 (define (get-wm-class window)
-  (let ((res (%wm-class (display-Xdisplay (window-display window))
-			(window-Xwindow window))))
-    (if res
-	res
-	(error "cannot get WM class hint"))))
+  (%wm-class (display-Xdisplay (window-display window))
+	     (window-Xwindow window)))
 
 (import-lambda-definition %wm-class (Xdisplay Xwindow)
   "scx_Wm_Class")
@@ -245,8 +243,9 @@
 (define (get-wm-hints window)
   (let ((res (%wm-hints (display-Xdisplay (window-display window))
 			(window-Xwindow window))))
-    (filter (lambda (x) (not (null? (cdr x))))
-	    ((integer+vector->wm-hint-alist (window-display window)) res))))
+    (if res
+	((integer+vector->wm-hint-alist (window-display window)) res)
+	#f)))
 
 (import-lambda-definition %wm-hints (Xdisplay Xwindow)
   "scx_Wm_Hints")
@@ -268,10 +267,13 @@
 ;; XGetTransientForHint.
 
 (define (get-transient-for window)
-  (make-window (%transient-for (display-Xdisplay (window-display window))
-			       (window-Xwindow window))
-	       (window-display window)
-	       #f))
+  (let ((Xwindow (%transient-for (display-Xdisplay (window-display window))
+				 (window-Xwindow window))))
+    (if (= 0 Xwindow)
+	#f
+	(make-window Xwindow
+		     (window-display window)
+		     #f))))
 
 (import-lambda-definition %transient-for (Xdisplay Xwindow)
   "scx_Transient_For")