--- takahashi.xul	2006/06/10 15:03:44	10
+++ takahashi.xul	2006/06/10 15:20:43	11
@@ -1099,9 +1099,18 @@
 	insertTextFor : function(aString, aNode, aPosOffset)
 	{
 		var pos = aNode.selectionStart;
+		var sel_len = aNode.selectionEnd - aNode.selectionStart;
 		var value = aNode.value;
-		aNode.value = [value.substring(0, pos), aString, value.substring(pos, value.length)].join('');
-		aNode.selectionEnd = aNode.selectionStart = pos + (aPosOffset || 0);
+		if (! aPosOffset) aPosOffset = 0;
+		aNode.value = [
+			value.substring(0, pos),
+			aString.substring(0,aPosOffset),
+			value.substring(pos, pos + sel_len),
+			aString.substring(aPosOffset, aString.length),
+			value.substring(pos + sel_len, value.length - sel_len)
+		].join('');
+		aNode.selectionStart = pos + (aPosOffset || 0);
+		aNode.selectionEnd = aNode.selectionStart + sel_len;
 	},