From 3c0d881a45dbfd1bb049e786059bb7154b8b1f26 Mon Sep 17 00:00:00 2001
From: Gwilym Kuiper <gw@ilym.me>
Date: Fri, 25 Jun 2021 21:57:24 +0100
Subject: [PATCH] Allow for volume control

---
 agb/src/sound/mixer/mod.rs      | 11 +++++++++++
 agb/src/sound/mixer/sw_mixer.rs |  4 ++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/agb/src/sound/mixer/mod.rs b/agb/src/sound/mixer/mod.rs
index 2ceb6349..f9e0dc90 100644
--- a/agb/src/sound/mixer/mod.rs
+++ b/agb/src/sound/mixer/mod.rs
@@ -30,6 +30,7 @@ pub struct SoundChannel {
     should_loop: bool,
 
     playback_speed: Num<usize, 8>,
+    volume: Num<i16, 4>, // between 0 and 1
 
     panning: Num<i16, 4>, // between -1 and 1
     is_done: bool,
@@ -47,6 +48,7 @@ impl SoundChannel {
             panning: 0.into(),
             is_done: false,
             priority: SoundPriority::Low,
+            volume: 1.into(),
         }
     }
 
@@ -59,6 +61,7 @@ impl SoundChannel {
             panning: 0.into(),
             is_done: false,
             priority: SoundPriority::High,
+            volume: 1.into(),
         }
     }
 
@@ -79,4 +82,12 @@ impl SoundChannel {
         self.panning = panning;
         self
     }
+
+    pub fn volume<'a>(&'a mut self, volume: Num<i16, 4>) -> &'a mut Self {
+        assert!(volume <= Num::new(1), "volume must be <= 1");
+        assert!(volume >= Num::new(0), "volume must be >= 0");
+
+        self.volume = volume;
+        self
+    }
 }
diff --git a/agb/src/sound/mixer/sw_mixer.rs b/agb/src/sound/mixer/sw_mixer.rs
index d7ac10ec..96b7dc1c 100644
--- a/agb/src/sound/mixer/sw_mixer.rs
+++ b/agb/src/sound/mixer/sw_mixer.rs
@@ -117,8 +117,8 @@ impl MixerBuffer {
                 continue;
             }
 
-            let right_amount = (channel.panning + 1) / 2;
-            let left_amount = -right_amount + 1;
+            let right_amount = ((channel.panning + 1) / 2) * channel.volume;
+            let left_amount = (-right_amount + 1) * channel.volume;
 
             if channel.pos + channel.playback_speed * SOUND_BUFFER_SIZE >= channel.data.len().into()
             {