Automatically add box2d contact listener

src/play_clj/g2d_physics.clj

@@ -1,22 +1,34 @@
 (ns play-clj.g2d-physics
   (:require [play-clj.math :as m]
             [play-clj.utils :as u])
-  (:import [com.badlogic.gdx.physics.box2d World]))
+  (:import [com.badlogic.gdx.physics.box2d ContactListener World]))
 
-(defn box2d*
+(defn box-2d*
   ([]
-    (box2d* 0 0 true))
+    (box-2d* 0 0 true))
   ([gravity-x gravity-y]
-    (box2d* gravity-x gravity-y true))
+    (box-2d* gravity-x gravity-y true))
   ([gravity-x gravity-y sleep?]
     (World. (m/vector-2 gravity-x gravity-y) sleep?)))
 
-(defmacro box2d
+(defmacro box-2d
   [gravity-x gravity-y & options]
-  `(let [object# (box2d* ~gravity-x ~gravity-y)]
+  `(let [object# (box-2d* ~gravity-x ~gravity-y)]
      (u/calls! ^World object# ~@options)
      object#))
 
-(defmacro box2d!
+(defmacro box-2d!
   [{:keys [^World world]} k & options]
   `(u/call! ^World ~world ~k ~@options))
+
+(defn contact-listener
+  [{:keys [on-begin-contact on-end-contact on-post-solve on-pre-solve]} execute-fn!]
+  (reify ContactListener
+    (beginContact [this c]
+      (execute-fn! on-begin-contact :contact c))
+    (endContact [this c]
+      (execute-fn! on-end-contact :contact c))
+    (postSolve [this c i]
+      (execute-fn! on-post-solve :contact c :impulse i))
+    (preSolve [this c m]
+      (execute-fn! on-pre-solve :contact c :old-manifold m))))