add on-goodbye-event

This change requires a coordinated change to the snip-lib pkg and to
the gui-lib package. The docs are in the gui-doc pkg and yet point to
the snip-pkg as the containing pkg, so I updated the version number
for snip-lib and left the version number for gui-lib alone

original commit: 4b92117a9fd6fb638240bc6e57e25bc9de138c53

pkgs/gui-pkgs/gui-doc/scribblings/gui/snip-class.scrbl

@@ -377,7 +377,8 @@ following symbols:
  @item{@indexed-racket['handles-all-mouse-events] --- this snip can
        handle mouse events that touch the snip or that immediately
        follow an event that touches the snip, even if the snip does
-       not have the keyboard focus}
+       not have the keyboard focus (see also
+       @method[snip% on-goodbye-event])}
 
  @item{@indexed-racket['width-depends-on-x] --- this snip's display
        width depends on the snip's x-@techlink{location} within the
@@ -632,6 +633,32 @@ Does nothing.
 
 }}
 
+@defmethod[(on-goodbye-event [dc (is-a?/c dc<%>)]
+                             [x real?]
+                             [y real?]
+                             [editorx real?]
+                             [editory real?]
+                             [event (is-a?/c mouse-event%)])
+           void?]{
+@methspec{
+
+Called to handle an event that is really aimed at another
+snip in order to give this snip a chance to clean up 
+as the mouse moves away. The arguments are the same
+as @method[snip% on-event].
+
+This method is called only when the snip has the
+@indexed-racket['handles-all-mouse-events] flag set
+(see @method[snip% get-flags] and @method[snip% set-flags]).
+
+}
+@methimpl{
+
+  Calls this object's @racket[_on-event] method
+
+}
+
+@history[#:added "1.1"]}
 
 @defmethod[(own-caret [own-it? any/c])
            void?]{

pkgs/gui-pkgs/gui-lib/mred/private/wxme/text.rkt

@@ -486,7 +486,7 @@
                        (not (eq? snip prev-mouse-snip)))
               (let-boxes ([x 0.0] [y 0.0])
                   (get-snip-position-and-location prev-mouse-snip #f x y)
-                (send prev-mouse-snip on-event dc (- x scrollx) (- y scrolly) x y event)))
+                (send prev-mouse-snip on-goodbye-event dc (- x scrollx) (- y scrolly) x y event)))
             (set! prev-mouse-snip #f)
             (if (and s-caret-snip (has-flag? (snip->flags s-caret-snip) HANDLES-EVENTS))
                 (let-boxes ([x 0.0] [y 0.0])