audio: Use values between 0 and 1 for volume.

Hide the weird SDL usage of 0 to 128.

* chickadee/audio.scm (set-sample-volume!, music-volume,
set-music-volume!): Translate to/from SDL's volume range.

1 files changed, 12 insertions, 9 deletions

diff --git a/chickadee/audio.scm b/chickadee/audio.scm
index d92ae94..c92eb44 100644
--- a/chickadee/audio.scm
+++ b/chickadee/audio.scm
@@ -77,9 +77,10 @@
         (error "cannot load audio sample:" file))))
 
 (define (set-sample-volume! volume)
-  "Set the volume that all samples are played at to VOLUME, an integer
-value between 0 and 128."
-  (ignore-value (sdl2:set-channel-volume! #f volume)))
+  "Set the volume that all samples are played at to VOLUME, a floating
+point value between 0 and 1."
+  (ignore-value
+   (sdl2:set-channel-volume! #f (inexact->exact (round (* volume 128.0))))))
 
 (define (play-sample sample)
   "Play SAMPLE."
@@ -105,14 +106,16 @@ value between 0 and 128."
   (make-music (sdl2:load-music file)))
 
 (define (music-volume)
-  "Return the volume level for music, an integer value between 0 and
-128."
-  (sdl2:music-volume))
+  "Return the volume level for music, a floating point value between
+0 and 1."
+  (/ (sdl2:music-volume) 128.0))
 
 (define (set-music-volume! volume)
-  "Set the volume that music is played at to VOLUME, an integer value
-between 0 and 128."
-  (ignore-value (sdl2:set-music-volume! volume)))
+  "Set the volume that music is played at to VOLUME, a floating point
+value between 0 and 1."
+  (ignore-value
+   (sdl2:set-music-volume!
+    (inexact->exact (round (* volume 128.0))))))
 
 (define* (play-music music #:key loop?)
   "Play MUSIC.  If LOOP?, play it over and over and over and over