From a68e15e27404629ce8301332416a0a74d13574de Mon Sep 17 00:00:00 2001
From: Sebastian Krzyszkowiak <dos@dosowisko.net>
Date: Tue, 20 Nov 2018 20:30:48 +0100
Subject: [PATCH] tween: add ability to store a custom tweening function with
 the Tween object

---
 src/tween.c | 6 ++++++
 src/tween.h | 5 ++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/tween.c b/src/tween.c
index c0b490e..241680b 100644
--- a/src/tween.c
+++ b/src/tween.c
@@ -256,6 +256,7 @@ SYMBOL_EXPORT struct Tween Tween(struct Game* game, double start, double stop, T
 		.predelay = 0,
 		.postdelay = 0,
 		.callback = NULL,
+		.func = NULL,
 		.data = NULL};
 }
 
@@ -340,11 +341,16 @@ SYMBOL_EXPORT double Interpolate(double pos, TWEEN_STYLE style) {
 			return BounceEaseOut(pos);
 		case TWEEN_STYLE_BOUNCE_IN_OUT:
 			return BounceEaseInOut(pos);
+		default:
+			return pos;
 	}
 	return pos;
 }
 
 SYMBOL_EXPORT double GetTweenInterpolation(struct Tween* tween) {
+	if (tween->style == TWEEN_STYLE_CUSTOM && tween->func) {
+		return tween->func(GetTweenPosition(tween));
+	}
 	return Interpolate(GetTweenPosition(tween), tween->style);
 }
 
diff --git a/src/tween.h b/src/tween.h
index 83d2224..d0a85aa 100644
--- a/src/tween.h
+++ b/src/tween.h
@@ -65,7 +65,9 @@ typedef enum TWEEN_STYLE {
 	// Exponentially-decaying bounce easing
 	TWEEN_STYLE_BOUNCE_IN,
 	TWEEN_STYLE_BOUNCE_OUT,
-	TWEEN_STYLE_BOUNCE_IN_OUT
+	TWEEN_STYLE_BOUNCE_IN_OUT,
+	// Custom callback
+	TWEEN_STYLE_CUSTOM
 } TWEEN_STYLE; // Cheet sheet at http://easings.net/ :)
 
 struct Tween {
@@ -76,6 +78,7 @@ struct Tween {
 	bool paused;
 	bool done;
 	struct Game* game;
+	double (*func)(double value);
 	void (*callback)(struct Game* game, struct Tween* tween, void* data);
 	void* data;
 };