From 6233cb8aaebe552b82a1911482929db9e0716650 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Mon, 3 May 2021 21:00:03 -0400
Subject: scene: Improve background music handling.

---
 starling/scene.scm | 32 ++++++++++++++++++++++----------
 1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/starling/scene.scm b/starling/scene.scm
index cda1e4e..16630ba 100644
--- a/starling/scene.scm
+++ b/starling/scene.scm
@@ -55,21 +55,33 @@
 
 (define-class <scene> (<node>)
   (background-music-source #:getter background-music-source
-                           #:init-form (make-source #:loop? #t))
+                           #:init-thunk make-source)
   (background-music #:accessor background-music #:init-form #f
-                    #:init-keyword #:music)
+                    #:init-keyword #:music #:asset? #t #:watch? #t)
   (background-music-volume #:accessor background-music-volume #:init-form 1.0
-                           #:init-keyword #:music-volume)
+                           #:init-keyword #:music-volume #:watch? #t)
   (background-music-loop? #:accessor background-music-loop? #:init-form #t
-                          #:init-keyword #:music-loop?))
+                          #:init-keyword #:music-loop? #:watch? #t))
+
+(define-method (refresh-background-music (scene <scene>))
+  (let ((source (background-music-source scene)))
+    (if (audio? (background-music scene))
+        (begin
+          (set-source-volume! source (background-music-volume scene))
+          (set-source-loop! source (background-music-loop? scene))
+          (set-source-audio! source (background-music scene))
+          (source-play source))
+        (source-stop (background-music-source scene)))))
+
+(define-method (on-change (scene <scene>) slot-name old new)
+  (case slot-name
+    ((background-music background-music-volume background-music-loop?)
+     (refresh-background-music scene))
+    (else
+     (next-method))))
 
 (define-method (on-enter (scene <scene>))
-  (when (audio? (background-music scene))
-    (set-source-volume! (background-music-source scene)
-                        (background-music-volume scene))
-    (set-source-audio! (background-music-source scene)
-                       (background-music scene))
-    (source-play (background-music-source scene))))
+  (refresh-background-music scene))
 
 (define-method (on-exit (scene <scene>))
   (source-stop (background-music-source scene)))
-- 
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