--- a/Rectangle.st	Wed Oct 06 21:32:48 1999 +0200
+++ b/Rectangle.st	Wed Oct 06 22:22:28 1999 +0200
@@ -1213,9 +1213,17 @@
      and the argument, aRectangle"
 
     ^ Rectangle left:(left min:(aRectangle left))
-	       right:((left + width) max:(aRectangle right))
-		 top:(top min:(aRectangle top))
-	      bottom:((top + height) max:(aRectangle bottom))
+               right:((left + width) max:(aRectangle right))
+                 top:(top min:(aRectangle top))
+              bottom:((top + height) max:(aRectangle bottom))
+
+    "
+     (Rectangle origin:10@10 corner:100@100)
+         merge:(Rectangle origin:20@20 corner:110@110)
+
+     (Rectangle origin:10@10 corner:100@100)
+         merge:(Rectangle origin:20@20 corner:100@100)
+    "
 !
 
 nonIntersections:aRectangle
@@ -1224,6 +1232,36 @@
     ^ self areasOutside:aRectangle
 !
 
+quickMerge: aRectangle 
+    "return the receiver if it encloses the given rectangle,
+     or the merge of the two rectangles if it doesn't. 
+     This method is an optimization to reduce extra rectangle creations."
+
+    | useRcvr rLeft rTop rRight rBottom Origin rCorner minX maxX minY maxY |
+
+    useRcvr := true.
+    rLeft := aRectangle left.
+    rTop := aRectangle top.
+    rRight := aRectangle right.
+    rBottom := aRectangle bottom.
+    minX := rLeft < left ifTrue: [useRcvr := false. rLeft] ifFalse: [left].
+    maxX := rRight > self right ifTrue: [useRcvr := false. rRight] ifFalse: [self right].
+    minY := rTop < top ifTrue: [useRcvr := false. rTop] ifFalse: [top].
+    maxY := rBottom > self bottom ifTrue: [useRcvr := false. rBottom] ifFalse: [self bottom].
+
+    useRcvr ifTrue: [^ self].
+    ^ Rectangle left:minX top:minY right:maxX bottom:maxY.
+
+    "
+     (Rectangle origin:10@10 corner:100@100)
+         quickMerge:(Rectangle origin:20@20 corner:110@110)
+
+     (Rectangle origin:10@10 corner:100@100)
+         quickMerge:(Rectangle origin:20@20 corner:100@100)
+    "
+
+!
+
 rounded
     "return a copy of the receiver with rounded coordinates"
 
@@ -1513,5 +1551,5 @@
 !Rectangle class methodsFor:'documentation'!
 
 version
-    ^ '$Header: /cvs/stx/stx/libbasic/Rectangle.st,v 1.58 1998-05-27 09:22:00 cg Exp $'
+    ^ '$Header: /cvs/stx/stx/libbasic/Rectangle.st,v 1.59 1999-10-06 20:22:28 cg Exp $'
 ! !