From a944f8c4f44ae85d184c49a29e6127154d87d5d9 Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Fri, 23 Jul 2021 23:28:16 +0300
Subject: [PATCH] Add geom::rotate_towards

---
 libs/geom/include/psemek/geom/math.hpp | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/libs/geom/include/psemek/geom/math.hpp b/libs/geom/include/psemek/geom/math.hpp
index 6894d080..573473b8 100644
--- a/libs/geom/include/psemek/geom/math.hpp
+++ b/libs/geom/include/psemek/geom/math.hpp
@@ -110,6 +110,7 @@ namespace psemek::geom
 		return std::pair{x1, x2};
 	}
 
+	// returns (a1 - a0)
 	template <typename T>
 	T angle_difference(T a0, T a1)
 	{
@@ -124,6 +125,17 @@ namespace psemek::geom
 		return std::atan2(y, x);
 	}
 
+	template <typename T>
+	T rotate_towards(T value, T target, T max_difference)
+	{
+		auto d = angle_difference(value, target);
+		if (d > max_difference)
+			d = max_difference;
+		if (d < -max_difference)
+			d = -max_difference;
+		return value + d;
+	}
+
 	template <typename T>
 	T idiv(T x, T m)
 	{