tween framerate

Co-Authored-By: George Kurelic <Gkurelic@gmail.com>

Author: cyn0x8

flixel/tweens/FlxTween.hx

@@ -505,6 +505,7 @@ class FlxTween implements IFlxDestroyable
 	public var active(default, set):Bool = false;
 	public var duration:Float = 0;
 	public var ease:EaseFunction;
+	public var framerate:Float;
 	public var onStart:TweenCallback;
 	public var onUpdate:TweenCallback;
 	public var onComplete:TweenCallback;
@@ -562,6 +563,7 @@ class FlxTween implements IFlxDestroyable
 		onUpdate = Options.onUpdate;
 		onComplete = Options.onComplete;
 		ease = Options.ease;
+		framerate = Options.framerate != null ? Options.framerate : 0;
 		setDelays(Options.startDelay, Options.loopDelay);
 		this.manager = manager != null ? manager : globalManager;
 	}
@@ -619,13 +621,23 @@ class FlxTween implements IFlxDestroyable
 
 	function update(elapsed:Float):Void
 	{
+		var preTick:Float = _secondsSinceStart;
 		_secondsSinceStart += elapsed;
+		var postTick:Float = _secondsSinceStart;
+
 		var delay:Float = (executions > 0) ? loopDelay : startDelay;
 		if (_secondsSinceStart < delay)
 		{
 			return;
 		}
-		scale = Math.max((_secondsSinceStart - delay), 0) / duration;
+
+		if (framerate > 0)
+		{
+			preTick = Math.fround(preTick * framerate) / framerate;
+			postTick = Math.fround(postTick * framerate) / framerate;
+		}
+
+		scale = Math.max((postTick - delay), 0) / duration;
 		if (ease != null)
 		{
 			scale = ease(scale);
@@ -647,7 +659,7 @@ class FlxTween implements IFlxDestroyable
 		}
 		else
 		{
-			if (onUpdate != null)
+			if (postTick > preTick && onUpdate != null)
 				onUpdate(this);
 		}
 	}
@@ -919,6 +931,12 @@ typedef TweenOptions =
 	 */
 	@:optional var ease:EaseFunction;
 
+	/**
+	 * Optional set framerate for this tween to update at.
+	 * This also affects how often `onUpdate` is called.
+	 */
+	@:optional var framerate:Null<Float>;
+
 	/**
 	 * Optional start callback function.
 	 */

flixel/tweens/misc/FlickerTween.hx

@@ -23,6 +23,13 @@ typedef FlickerTweenOptions =
 	 */
 	@:optional var ease:EaseFunction;
 
+	/**
+	 * Optional set framerate for this tween to update at.
+	 * This also affects how often `onUpdate` is called.
+	 * Not to be confused with `period` for flickering.
+	 */
+	@:optional var framerate:Null<Float>;
+	
 	/**
 	 * Optional start callback function.
 	 */

tests/unit/src/flixel/tweens/FlxTweenTest.hx

@@ -4,6 +4,7 @@ import flixel.FlxBasic;
 import flixel.FlxG;
 import flixel.math.FlxPoint;
 import flixel.tweens.FlxTween.TweenCallback;
+import flixel.tweens.FlxTween.TweenOptions;
 import flixel.util.FlxTimer;
 import massive.munit.Assert;
 
@@ -432,6 +433,35 @@ class FlxTweenTest extends FlxTest
 		Assert.isTrue(tween3Updated);
 	}
 
+	function assertTweenUpdates(duration:Float, ?fps:Float, ?options:TweenOptions, expected:Int)
+	{
+		var updates = 0;
+		
+		if (options == null)
+			options = {};
+
+		if (fps != null)
+			options.framerate = fps;
+
+		options.onUpdate = function(_) updates++;
+		options.onComplete = function(_) Assert.areEqual(expected, updates);
+		FlxTween.tween({value: 0.0}, {value: 1}, 2.0, options);
+	}
+
+	@Test
+	function testTweenFramerate()
+	{
+		assertTweenUpdates(2.0, null, null, 60);
+		assertTweenUpdates(2.0, 0, null, 60);
+		assertTweenUpdates(2.0, 5, null, 10);
+		assertTweenUpdates(2.0, 10, {startDelay: 0.5}, 20);
+		assertTweenUpdates(2.0, 10.1, null, 21);
+		assertTweenUpdates(2.0, 29.9, null, 60);
+		assertTweenUpdates(2.0, 100, null, 60);
+
+		step(FlxG.updateFramerate * 3); // 3 full seconds
+	}
+
 	function makeTween(duration:Float, onComplete:TweenCallback, ?onUpdate:TweenCallback):FlxTween
 	{
 		var foo = {f: 0};