--- a/GraphicsContext.st	Fri Feb 10 11:19:43 2017 +0100
+++ b/GraphicsContext.st	Fri Feb 10 11:20:30 2017 +0100
@@ -495,6 +495,16 @@
     ^ #round
 ! !
 
+!GraphicsContext class methodsFor:'queries'!
+
+isAbstract
+    "Return if this class is an abstract class.
+     True is returned here for myself only; false for subclasses.
+     Abstract subclasses must redefine this again."
+
+    ^ self == GraphicsContext.
+! !
+
 !GraphicsContext methodsFor:'Compatibility-ST80'!
 
 displayArc:origin radius:radius from:startAngle angle:angle