Index: main/window/generic.lisp
===================================================================
--- main/window/generic.lisp	(revision main,50)
+++ main/window/generic.lisp	(revision main,66)
@@ -51,8 +51,9 @@
 
 
-(defun size (window)
-  (let ((ptr (window-pointer window)))
-    (values (getmaxy ptr)
-            (getmaxx ptr))))
+(defgeneric size (window)
+  (:method ((window window))
+    (let ((ptr (window-pointer window)))
+      (values (getmaxy ptr)
+              (getmaxx ptr)))))
 
 (defun erase (window)