From 705a5138580296a225df05a143e2f5d195c3024e Mon Sep 17 00:00:00 2001
From: Tim Blechmann <tim@klingt.org>
Date: Sat, 15 Sep 2012 18:10:30 +0200
Subject: [PATCH] class library: guard Document-*listener and
 Document-isListener

Signed-off-by: Tim Blechmann <tim@klingt.org>
---
 SCClassLibrary/Common/GUI/Document.sc | 31 ++++++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)

diff --git a/SCClassLibrary/Common/GUI/Document.sc b/SCClassLibrary/Common/GUI/Document.sc
index 5f82a5588..5937037d4 100644
--- a/SCClassLibrary/Common/GUI/Document.sc
+++ b/SCClassLibrary/Common/GUI/Document.sc
@@ -23,9 +23,9 @@ Document {
 	var <envir, savedEnvir;
 	var <editable;
 
-	  *initClass{
+	*initClass{
 		allDocuments = [];
-	  }
+	}
 
 	*startup {
 		var num, doc;
@@ -162,10 +162,21 @@ Document {
 	}
 
 	*listener {
-		^allDocuments[this.implementationClass.prGetIndexOfListener];
+		var index = this.prGetIndexOfListener;
+		if (index.notNil) {
+			^allDocuments[index];
+		} {
+			^nil
+		}
 	}
+
 	isListener {
-		^allDocuments.indexOf(this) == this.class.prGetIndexOfListener
+		var index = this.class.prGetIndexOfListener;
+		if (index.notNil) {
+			^allDocuments.indexOf(this) == index
+		} {
+			^False
+		}
 	}
 
 // document setup
@@ -710,9 +721,16 @@ Document {
 	}
 
 	*prGetIndexOfListener {
-		^this.subclassResponsibility(thisMethod)
-	}
+		if (this.implementationClass.isNil) {
+			^nil
+		};
 
+		if (this.implementationClass.respondsTo(\prGetIndexOfListener)) {
+			^this.implementationClass.prGetIndexOfListener
+		} {
+			^nil
+		}
+	}
 
 	//---not yet implemented
 	// ~/Documents
@@ -755,5 +773,4 @@ Document {
 	*prBasicNew {
 		^super.new
 	}
-
 }
-- 
2.11.4.GIT