Cleaned up eventhook business. Replaced with multi-method that's much…

… cleaner.

src/seesaw/event.clj

@@ -372,14 +372,32 @@
     []
     targets))
 
-(defprotocol EventHook
-  (add-listener [this event-name event-handler]))
+(defmulti listen-for-named-event
+  "*experimental and subject to change*
 
-(extend-protocol EventHook
-  Object
-  (add-listener 
-    [this event-name event-handler] 
-    nil))
+  A multi-method that allows the set of events in the (listen) to be extended or
+  for an existing event to be extended to a new type. Basically performs
+  double-dispatch on the type of the target and the name of the event.
+
+  This multi-method is an extension point, but is not meant to be called directly
+  by client code.
+
+  Register the given event handler on this for the given event
+  name which is a keyword like :selection, etc. If the handler
+  is registered, returns a zero-arg function that undoes the
+  listener. Otherwise, must return nil indicating that no listener
+  was registered, i.e. this doesn't support the given event.
+
+  TODO try using this to implement all of the event system rather than the mess
+  above.
+
+  See:
+    (seesaw.swingx/color-selection-button) for an example.
+  "
+  (fn [this event-name event-fn] [(type this) event-name]))
+
+; Default impl just returns nil indicating no special handling for the event.
+(defmethod listen-for-named-event :default [this event-name event-fn] nil)
 
 (defn- single-target-listen-impl
   "Takes:
@@ -413,7 +431,7 @@
   ([targets raw-event-name event-fn]
     (apply concat 
       (for [target targets] 
-        (if-let [hook-result (add-listener target raw-event-name event-fn)]
+        (if-let [hook-result (listen-for-named-event target raw-event-name event-fn)]
           [hook-result]
           (single-target-listen-impl target raw-event-name event-fn)))))
 

src/seesaw/swingx.clj

@@ -19,7 +19,7 @@
   (:use [seesaw.util :only [to-uri resource constant-map illegal-argument]]
         [seesaw.icon :only [icon]]
         [seesaw.selection :only [Selection ViewModelIndexConversion]]
-        [seesaw.event :only [EventHook listen-to-property]]
+        [seesaw.event :only [listen-for-named-event listen-to-property]]
         [seesaw.core :only [construct to-widget
                             abstract-panel
                             border-panel-options
@@ -457,17 +457,17 @@
     args 
     color-selection-button-options))
 
+; Extend selection and selection event stuff for color button.
+
 (extend-protocol Selection
   org.jdesktop.swingx.JXColorSelectionButton
     (get-selection [this] [(config this :selection)])
     (set-selection [this [v]] (config! this :selection v)))
 
-(extend-protocol EventHook
-  org.jdesktop.swingx.JXColorSelectionButton
-    (add-listener [this event-name event-fn]
-      (condp = event-name
-        :selection (listen-to-property this "background" event-fn)
-        nil)))
+(defmethod listen-for-named-event 
+  [org.jdesktop.swingx.JXColorSelectionButton :selection]
+  [this event-name event-fn]
+  (listen-to-property this "background" event-fn))
 
 ;*******************************************************************************
 ; Header

test/seesaw/test/event.clj

@@ -304,3 +304,16 @@
                    :tree-will-collapse #(reset! will-collapse %))
       (expect (not (or @will-expand @will-collapse))))))
 
+(describe listen-to-property
+  (it "registers a property change listener"
+    (let [b (javax.swing.JButton.)
+          called (atom nil)
+          remove-fn (listen-to-property b "text"
+                                        (fn [e] (reset! called e)))]
+      (.setText b "HI")
+      (expect @called)
+      (reset! called nil)
+      (remove-fn)
+      (.setText b "BYE")
+      (expect (nil? @called)))))
+