Remove the ability to ignore global volume (#11092)

# Objective

The ability to ignore the global volume doesn't seem desirable and
complicates the API.

#7706 added global volume and the ability to ignore it, but there was no
further discussion about whether that's useful. Feel free to discuss
here :)

## Solution

Replace the `Volume` type's functionality with the `VolumeLevel`. Remove
`VolumeLevel`.

I also removed `DerefMut` derive that effectively made the volume `pub`
and actually ensured that the volume isn't set below `0` even in release
builds.

## Migration Guide

The option to ignore the global volume using `Volume::Absolute` has been
removed and `Volume` now stores the volume level directly, removing the
need for the `VolumeLevel` struct.

crates/bevy_audio/src/audio.rs

@@ -1,59 +1,33 @@
 use crate::{AudioSource, Decodable};
 use bevy_asset::{Asset, Handle};
-use bevy_derive::{Deref, DerefMut};
+use bevy_derive::Deref;
 use bevy_ecs::prelude::*;
 use bevy_math::Vec3;
 use bevy_reflect::prelude::*;
 
-/// Defines the volume to play an audio source at.
-#[derive(Clone, Copy, Debug, Reflect)]
-pub enum Volume {
-    /// A volume level relative to the global volume.
-    Relative(VolumeLevel),
-    /// A volume level that ignores the global volume.
-    Absolute(VolumeLevel),
-}
-
-impl Default for Volume {
-    fn default() -> Self {
-        Self::Relative(VolumeLevel::default())
-    }
-}
-
-impl Volume {
-    /// Create a new volume level relative to the global volume.
-    pub fn new_relative(volume: f32) -> Self {
-        Self::Relative(VolumeLevel::new(volume))
-    }
-    /// Create a new volume level that ignores the global volume.
-    pub fn new_absolute(volume: f32) -> Self {
-        Self::Absolute(VolumeLevel::new(volume))
-    }
-}
-
 /// A volume level equivalent to a non-negative float.
-#[derive(Clone, Copy, Deref, DerefMut, Debug, Reflect)]
-pub struct VolumeLevel(pub(crate) f32);
+#[derive(Clone, Copy, Deref, Debug, Reflect)]
+pub struct Volume(pub(crate) f32);
 
-impl Default for VolumeLevel {
+impl Default for Volume {
     fn default() -> Self {
         Self(1.0)
     }
 }
 
-impl VolumeLevel {
+impl Volume {
     /// Create a new volume level.
     pub fn new(volume: f32) -> Self {
         debug_assert!(volume >= 0.0);
-        Self(volume)
+        Self(f32::max(volume, 0.))
     }
     /// Get the value of the volume level.
     pub fn get(&self) -> f32 {
         self.0
     }
 
     /// Zero (silent) volume level
-    pub const ZERO: Self = VolumeLevel(0.0);
+    pub const ZERO: Self = Volume(0.0);
 }
 
 /// The way Bevy manages the sound playback.
@@ -106,7 +80,7 @@ impl PlaybackSettings {
     /// Will play the associated audio source once.
     pub const ONCE: PlaybackSettings = PlaybackSettings {
         mode: PlaybackMode::Once,
-        volume: Volume::Relative(VolumeLevel(1.0)),
+        volume: Volume(1.0),
         speed: 1.0,
         paused: false,
         spatial: false,
@@ -115,28 +89,19 @@ impl PlaybackSettings {
     /// Will play the associated audio source in a loop.
     pub const LOOP: PlaybackSettings = PlaybackSettings {
         mode: PlaybackMode::Loop,
-        volume: Volume::Relative(VolumeLevel(1.0)),
-        speed: 1.0,
-        paused: false,
-        spatial: false,
+        ..PlaybackSettings::ONCE
     };
 
     /// Will play the associated audio source once and despawn the entity afterwards.
     pub const DESPAWN: PlaybackSettings = PlaybackSettings {
         mode: PlaybackMode::Despawn,
-        volume: Volume::Relative(VolumeLevel(1.0)),
-        speed: 1.0,
-        paused: false,
-        spatial: false,
+        ..PlaybackSettings::ONCE
     };
 
     /// Will play the associated audio source once and remove the audio components afterwards.
     pub const REMOVE: PlaybackSettings = PlaybackSettings {
         mode: PlaybackMode::Remove,
-        volume: Volume::Relative(VolumeLevel(1.0)),
-        speed: 1.0,
-        paused: false,
-        spatial: false,
+        ..PlaybackSettings::ONCE
     };
 
     /// Helper to start in a paused state.
@@ -196,21 +161,21 @@ impl SpatialListener {
     }
 }
 
-/// Use this [`Resource`] to control the global volume of all audio with a [`Volume::Relative`] volume.
+/// Use this [`Resource`] to control the global volume of all audio.
 ///
 /// Note: changing this value will not affect already playing audio.
 #[derive(Resource, Default, Clone, Copy, Reflect)]
 #[reflect(Resource)]
 pub struct GlobalVolume {
     /// The global volume of all audio.
-    pub volume: VolumeLevel,
+    pub volume: Volume,
 }
 
 impl GlobalVolume {
     /// Create a new [`GlobalVolume`] with the given volume.
     pub fn new(volume: f32) -> Self {
         Self {
-            volume: VolumeLevel::new(volume),
+            volume: Volume::new(volume),
         }
     }
 }

crates/bevy_audio/src/audio_output.rs

@@ -1,6 +1,6 @@
 use crate::{
     AudioSourceBundle, Decodable, GlobalVolume, PlaybackMode, PlaybackSettings, SpatialAudioSink,
-    SpatialListener, SpatialScale, Volume,
+    SpatialListener, SpatialScale,
 };
 use bevy_asset::{Asset, Assets, Handle};
 use bevy_ecs::{prelude::*, system::SystemParam};
@@ -159,10 +159,7 @@ pub(crate) fn play_queued_audio_system<Source: Asset + Decodable>(
             };
 
             sink.set_speed(settings.speed);
-            match settings.volume {
-                Volume::Relative(vol) => sink.set_volume(vol.0 * global_volume.volume.0),
-                Volume::Absolute(vol) => sink.set_volume(vol.0),
-            }
+            sink.set_volume(settings.volume.0 * global_volume.volume.0);
 
             if settings.paused {
                 sink.pause();
@@ -202,10 +199,7 @@ pub(crate) fn play_queued_audio_system<Source: Asset + Decodable>(
             };
 
             sink.set_speed(settings.speed);
-            match settings.volume {
-                Volume::Relative(vol) => sink.set_volume(vol.0 * global_volume.volume.0),
-                Volume::Absolute(vol) => sink.set_volume(vol.0),
-            }
+            sink.set_volume(settings.volume.0 * global_volume.volume.0);
 
             if settings.paused {
                 sink.pause();

crates/bevy_audio/src/lib.rs

@@ -63,7 +63,7 @@ struct AudioPlaySet;
 /// Insert an [`AudioBundle`] onto your entities to play audio.
 #[derive(Default)]
 pub struct AudioPlugin {
-    /// The global volume for all audio entities with a [`Volume::Relative`] volume.
+    /// The global volume for all audio entities.
     pub global_volume: GlobalVolume,
     /// The scale factor applied to the positions of audio sources and listeners for
     /// spatial audio.
@@ -72,12 +72,11 @@ pub struct AudioPlugin {
 
 impl Plugin for AudioPlugin {
     fn build(&self, app: &mut App) {
-        app.register_type::<VolumeLevel>()
+        app.register_type::<Volume>()
             .register_type::<GlobalVolume>()
             .register_type::<SpatialListener>()
             .register_type::<SpatialScale>()
             .register_type::<PlaybackMode>()
-            .register_type::<Volume>()
             .register_type::<PlaybackSettings>()
             .insert_resource(self.global_volume)
             .insert_resource(self.spatial_scale)