don't create undo point when no changes have been made

rebuild.e

@@ -2936,6 +2936,8 @@ ENDPROC
 
 PROC addUndo()
   DEF strStream:PTR TO stringStreamer
+  DEF prevStream:PTR TO stringStreamer
+  DEF doAdd=FALSE,i
   WHILE undoPos<(undoData.count()-1)
     strStream:=undoData.item(undoData.count()-1)
     END strStream
@@ -2946,8 +2948,20 @@ PROC addUndo()
 
   NEW strStream.create()
   saveStream(strStream)
-  undoData.add(strStream)
-  undoPos++
+
+  IF (undoData.count()=0) 
+    doAdd:=TRUE
+  ELSE
+    prevStream:=undoData.item(undoData.count()-1)
+    IF prevStream.compareTo(strStream)=FALSE THEN doAdd:=TRUE
+  ENDIF
+
+  IF doAdd
+    undoData.add(strStream)
+    undoPos++
+  ELSE
+    END strStream
+  ENDIF
 
   menuDisable(win,MENU_EDIT,MENU_EDIT_UNDO,0,undoPos=0)
   menuDisable(win,MENU_EDIT,MENU_EDIT_REDO,0,undoPos>=(undoData.count()-1))

stringStreamer.e

@@ -58,3 +58,16 @@ PROC reset() OF stringStreamer
   self.currpos:=0
 ENDPROC
 
+PROC compareTo(otherStream:PTR TO stringStreamer) OF stringStreamer
+  DEF i
+
+  IF otherStream.data.count()<>self.data.count()
+    RETURN FALSE
+  ELSE
+    i:=otherStream.data.count()-1
+    WHILE (i>=0)
+      IF StrCmp(otherStream.data.item(i),self.data.item(i))=FALSE THEN RETURN FALSE
+      i--
+    ENDWHILE
+  ENDIF    
+ENDPROC TRUE