changed the way equal<%> and snip% interact. Specifically:

- snip% now implements equal<%>
   its equal-to? delegates to other-equal-to?.

 - snip%'s other-equal-to and equal-hash-code and
   equal-secondary-hash-code all just amount to using eq?. The
   setup is here just to make snip% be the one that declares
   that it implements equal<%> so that various snips can adjust
   other-equal-to? (and the hash code methods)

 - image-snip% no longer implements equal<%>
   (but it extends snip% and it overrides other-equal-to?
    and the hash-code methods to do what they always did)

collects/racket/snip/private/snip.rkt

@@ -108,7 +108,7 @@
 
 ;; ------------------------------------------------------------
 
-(defclass snip% object%
+(defclass* snip% object% (equal<%>)
   ;; For use only by the owning editor:
   (field [s-prev #f]
          [s-next #f]
@@ -322,14 +322,19 @@
                 #f))))
 
   (def/public (set-unmodified)
-    (void)))
-
+    (void))
+  
+  (def/public (equal-to? [snip% that] [any? recur]) 
+    (send that other-equal-to? this recur))
+  (def/public (other-equal-to? [image-snip% that] [any? recur]) (eq? this that))
+  (define/public (equal-hash-code-of recur) (eq-hash-code this))
+  (define/public (equal-secondary-hash-code-of recur) 1))
+ 
 (defclass internal-snip% snip%
   (super-new)
   (def/override (set-count [exact-integer? c])
     ;; reject change
     (void)))
-
 ;; ------------------------------------------------------------
 
 (defclass string-snip-class% snip-class%
@@ -863,7 +868,7 @@
                        (get-output-bytes s))]
                     [else default]))])))
 
-(defclass* image-snip% internal-snip% (equal<%> png-convertible<%>)
+(defclass* image-snip% internal-snip% (png-convertible<%>)
   (inherit-field s-admin
                  s-flags)
   (inherit set-snipclass)
@@ -1138,10 +1143,7 @@
   (def/public (get-bitmap-mask)
     mask)
 
-  (def/public (equal-to? [image-snip% other] [any? recur])
-    (send other other-equal-to? this recur))
-
-  (def/public (other-equal-to? [image-snip% other] [any? recur])
+  (def/override (other-equal-to? [image-snip% other] [any? recur])
     (let* ([bm (send this get-bitmap)]
            [bm2 (send other get-bitmap)])
       (and
@@ -1186,9 +1188,9 @@
             (hash-code s1)))
         0))
 
-  (def/public (equal-hash-code-of [any? recur])
+  (def/override (equal-hash-code-of [any? recur])
     (do-hash-code equal-hash-code))
-  (def/public (equal-secondary-hash-code-of [any? recur])
+  (def/override (equal-secondary-hash-code-of [any? recur])
     (do-hash-code equal-secondary-hash-code))
 
   (def/public (set-offset [real? x] [real? y])

collects/scribblings/gui/image-snip-class.scrbl

@@ -1,7 +1,7 @@
 #lang scribble/doc
 @(require "common.ss")
 
-@defclass/title[image-snip% snip% (equal<%>)]{
+@defclass/title[image-snip% snip% ()]{
 
 An @scheme[image-snip%] is a snip that can display bitmap images
  (usually loaded from a file). When the image file cannot be found, a
@@ -43,19 +43,6 @@ secondary hash code for @this-obj[] (using the same notion of
 
 See also @scheme[equal<%>].}
 
-
-@defmethod[(equal-to? [snip (is-a?/c image-snip%)]
-                      [equal? (any/c any/c . -> . boolean?)])
-           boolean?]{
-
-Calls the @method[image-snip% other-equal-to?] method of @scheme[snip]
-(to simulate multi-method dispatch) in case @scheme[snip] provides a
-more specific equivalence comparison.
-
-See also @scheme[equal<%>].}
-
-
-
 @defmethod[(get-bitmap)
            (or/c (is-a?/c bitmap%) #f)]{
 
@@ -145,7 +132,7 @@ If @scheme[inline?] is not @scheme[#f], the image data will be saved
            boolean?]{
 
 Returns @scheme[#t] if @this-obj[] and @scheme[snip] both have bitmaps
-and the bitmaps are the same dimensions. If either has a mask bitmap
+and the bitmaps are the same. If either has a mask bitmap
 with the same dimensions as the main bitmap, then the masks must be
 the same (or if only one mask is present, it must correspond to a
 solid mask).

collects/scribblings/gui/snip-class.scrbl

@@ -1,7 +1,7 @@
 #lang scribble/doc
 @(require "common.ss")
 
-@defclass/title[snip% object% ()]{
+@defclass/title[snip% object% (equal<%>)]{
 
 A direct instance of @scheme[snip%] is uninteresting. Useful snips are
  defined by instantiating derived subclasses, but this class defines
@@ -217,7 +217,35 @@ Draws nothing.
 
 }}
 
+@defmethod[(equal-to? [snip (is-a?/c snip%)]
+                      [equal? (-> any/c any/c boolean?)])
+           boolean?]{
+@methspec{See @scheme[equal<%>].}
 
+@methimpl{Calls the @method[snip% other-equal-to?] method of @scheme[snip]
+(to simulate multi-method dispatch) in case @scheme[snip] provides a
+more specific equivalence comparison.}}
+
+@defmethod[(other-equal-to? [that (is-a?/c snip%)]
+                            [equal? (-> any/c any/ boolean?)])
+           boolean?]{
+@methimpl{Returns @racket[(eq? this that)].}
+}
+
+@defmethod[(equal-hash-code [hash-code (any/c . -> . exact-integer?)])
+           exact-integer?]{
+
+@methspec{See @scheme[equal<%>].}
+ 
+@methimpl{Returns @scheme[(eq-hash-code this)].}}
+
+@defmethod[(equal-secondary-hash-code [hash-code (any/c . -> . exact-integer?)])
+           exact-integer?]{
+
+@methspec{See @scheme[equal<%>].}
+ 
+@methimpl{Returns @scheme[1].}}
+                    
 @defmethod[(find-scroll-step [y real?])
            exact-nonnegative-integer?]{
 
@@ -234,7 +262,6 @@ Returns @scheme[0].
 
 }}
 
-
 @defmethod[(get-admin)
            (or/c (is-a?/c snip-admin%) false/c)]{