From 82f75f966b1d8c02ac87b0030a724855c31881af Mon Sep 17 00:00:00 2001
From: Thomas White <taw@physics.org>
Date: Sat, 22 May 2021 15:03:11 +0200
Subject: Add make-back-button

---
 examples/demo.scm                           |  4 ++++
 guile/starlet/midi-control/button-utils.scm | 11 ++++++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/examples/demo.scm b/examples/demo.scm
index a49bf7b..4ae93c6 100644
--- a/examples/demo.scm
+++ b/examples/demo.scm
@@ -266,14 +266,18 @@
 ;; Set up MIDI controller buttons to run cues
 (make-go-button pb 12)
 (make-stop-button pb 24)
+(make-back-button pb 28)
 (send-note-on 20)
 (send-note-on 24)
+(send-note-on 28)
 
 ;; A second set of go/stop buttons, because this works well on my controller
 (make-go-button pb 15)
 (make-stop-button pb 27)
+(make-back-button pb 31)
 (send-note-on 23)
 (send-note-on 27)
+(send-note-on 31)
 
 
 ;; Set up some buttons for quick access to fixtures
diff --git a/guile/starlet/midi-control/button-utils.scm b/guile/starlet/midi-control/button-utils.scm
index 051935f..859412d 100644
--- a/guile/starlet/midi-control/button-utils.scm
+++ b/guile/starlet/midi-control/button-utils.scm
@@ -24,6 +24,7 @@
   #:use-module (starlet playback)
   #:export (make-go-button
             make-stop-button
+            make-back-button
             select-on-button))
 
 
@@ -40,7 +41,15 @@
     (register-midi-note-callback!
      #:channel channel
      #:note-number button
-     #:func (lambda () (display "Stop/back!\n"))))
+     #:func (lambda () (stop! pb))))
+
+
+(define* (make-back-button pb button
+                           #:key (channel #f))
+    (register-midi-note-callback!
+     #:channel channel
+     #:note-number button
+     #:func (lambda () (back! pb))))
 
 
 (define* (select-on-button button fixture
-- 
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