Add onVolumeChange to SoundFrontEnd (HaxeFlixel#3148)

* Add onVolumeChange to SoundFrontEnd

* Move import inside conditional

* deprecate old func

* simplify import

* remove deprecation warnings

* fix typo in @:deprecated

---------

Co-authored-by: George Kurelic <[email protected]>

flixel/system/frontEnds/SoundFrontEnd.hx

@@ -9,6 +9,7 @@ import flixel.system.FlxAssets;
 import flixel.sound.FlxSound;
 import flixel.sound.FlxSoundGroup;
 import flixel.system.ui.FlxSoundTray;
+import flixel.util.FlxSignal;
 import openfl.Assets;
 import openfl.media.Sound;
 #if (openfl >= "8.0.0")
@@ -35,8 +36,14 @@ class SoundFrontEnd
 	 * Set this hook to get a callback whenever the volume changes.
 	 * Function should take the form myVolumeHandler(volume:Float).
 	 */
+	@:deprecated("volumeHandler is deprecated, use onVolumeChange, instead")
 	public var volumeHandler:Float->Void;
 
+	/**
+	 * A signal that gets dispatched whenever the volume changes.
+	 */
+	public var onVolumeChange(default, null):FlxTypedSignal<Float->Void> = new FlxTypedSignal<Float->Void>();
+
 	#if FLX_KEYBOARD
 	/**
 	 * The key codes used to increase volume (see FlxG.keys for the keys available).
@@ -328,6 +335,7 @@ class SoundFrontEnd
 	/**
 	 * Toggles muted, also activating the sound tray.
 	 */
+	@:haxe.warning("-WDeprecated")
 	public function toggleMuted():Void
 	{
 		muted = !muted;
@@ -337,6 +345,8 @@ class SoundFrontEnd
 			volumeHandler(muted ? 0 : volume);
 		}
 
+		onVolumeChange.dispatch(muted ? 0 : volume);
+
 		showSoundTray(true);
 	}
 
@@ -448,15 +458,18 @@ class SoundFrontEnd
 	}
 	#end
 
+	@:haxe.warning("-WDeprecated")
 	function set_volume(Volume:Float):Float
 	{
 		Volume = FlxMath.bound(Volume, 0, 1);
 
 		if (volumeHandler != null)
 		{
-			var param:Float = muted ? 0 : Volume;
-			volumeHandler(param);
+			volumeHandler(muted ? 0 : Volume);
 		}
+
+		onVolumeChange.dispatch(muted ? 0 : Volume);
+
 		return volume = Volume;
 	}
 }