From d83a7ecb4dbbcbf1bb7df7724414a6f3e7eef13f Mon Sep 17 00:00:00 2001
From: Alula <julekonopinska@gmail.com>
Date: Fri, 4 Sep 2020 14:00:09 +0200
Subject: [PATCH] audio timescale support

---
 src/sound/mod.rs      | 19 +++++++++++++++++--
 src/sound/playback.rs |  5 +++++
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/src/sound/mod.rs b/src/sound/mod.rs
index 98e01d7..b835d4e 100644
--- a/src/sound/mod.rs
+++ b/src/sound/mod.rs
@@ -6,11 +6,12 @@ use cpal::traits::{DeviceTrait, HostTrait, StreamTrait};
 
 use crate::engine_constants::EngineConstants;
 use crate::ggez::{Context, filesystem, GameResult};
-use crate::ggez::GameError::AudioError;
+use crate::ggez::GameError::{AudioError, InvalidValue};
 use crate::sound::organya::Song;
 use crate::sound::playback::{PlaybackEngine, SavedPlaybackState};
 use crate::sound::wave_bank::SoundBank;
 use crate::str;
+use cpal::Sample;
 
 pub mod pixtone;
 mod wave_bank;
@@ -126,11 +127,21 @@ impl SoundManager {
 
         Ok(())
     }
+
+    pub fn set_speed(&mut self, speed: f32) -> GameResult {
+        if speed <= 0.0 {
+            return Err(InvalidValue(str!("Speed must be bigger than 0.0!")));
+        }
+        self.tx.send(PlaybackMessage::SetSpeed(speed))?;
+
+        Ok(())
+    }
 }
 
 enum PlaybackMessage {
     Stop,
     PlaySong(Box<Song>),
+    SetSpeed(f32),
     SaveState,
     RestoreState,
 }
@@ -177,6 +188,10 @@ fn run<T>(rx: Receiver<PlaybackMessage>, bank: SoundBank,
                 Ok(PlaybackMessage::Stop) => {
                     state = PlaybackState::Stopped;
                 }
+                Ok(PlaybackMessage::SetSpeed(speed)) => {
+                    assert!(speed > 0.0);
+                    engine.set_sample_rate((sample_rate / speed) as usize);
+                }
                 Ok(PlaybackMessage::SaveState) => {
                     saved_state = Some(engine.get_state());
                 }
@@ -212,7 +227,7 @@ fn run<T>(rx: Receiver<PlaybackMessage>, bank: SoundBank,
                     }
                 };
 
-                let value: T = cpal::Sample::from::<u16>(&sample);
+                let value: T = Sample::from::<u16>(&sample);
                 for sample in frame.iter_mut() {
                     *sample = value;
                 }
diff --git a/src/sound/playback.rs b/src/sound/playback.rs
index 72246a3..452801c 100644
--- a/src/sound/playback.rs
+++ b/src/sound/playback.rs
@@ -103,8 +103,13 @@ impl PlaybackEngine {
     }
 
     pub fn set_sample_rate(&mut self, sample_rate: usize) {
+        self.frames_this_tick = (self.frames_this_tick as f32 * (self.output_format.sample_rate as f32 / sample_rate as f32)) as usize;
         self.output_format.sample_rate = sample_rate as u32;
         self.frames_per_tick = (sample_rate / 1000) * self.song.time.wait as usize;
+
+        if self.frames_this_tick >= self.frames_per_tick {
+            self.frames_this_tick = 0;
+        }
     }
 
     pub fn get_state(&self) -> SavedPlaybackState {