Add util::updater and smooth_updater

libs/util/include/psemek/util/smooth_updater.hpp

@@ -0,0 +1,67 @@
+#pragma once
+
+#include <psemek/util/updater.hpp>
+
+#include <cmath>
+
+namespace psemek::util
+{
+
+	template <typename Time, typename Value = Time>
+	struct smooth_updater
+		: updater<Time>
+	{
+		smooth_updater(Value & value, Time speed)
+			: value_(value)
+			, target_(value)
+			, speed_(speed)
+		{}
+
+		template <typename H>
+		smooth_updater & operator = (H new_value)
+		{
+			target_ = new_value;
+			return *this;
+		}
+
+		template <typename H>
+		smooth_updater & operator += (H new_value)
+		{
+			target_ += new_value;
+			return *this;
+		}
+
+		template <typename H>
+		smooth_updater & operator -= (H new_value)
+		{
+			target_ -= new_value;
+			return *this;
+		}
+
+		template <typename H>
+		smooth_updater & operator *= (H new_value)
+		{
+			target_ *= new_value;
+			return *this;
+		}
+
+		template <typename H>
+		smooth_updater & operator /= (H new_value)
+		{
+			target_ /= new_value;
+			return *this;
+		}
+
+		void update(Time dt) override
+		{
+			using std::lerp;
+			value_ = lerp(target_, value_, std::exp(- dt * speed_));
+		}
+
+	private:
+		Value & value_;
+		Value target_;
+		Time speed_;
+	};
+
+}

libs/util/include/psemek/util/updater.hpp

@@ -0,0 +1,14 @@
+#pragma once
+
+namespace psemek::util
+{
+
+	template <typename Time>
+	struct updater
+	{
+		virtual void update(Time dt) = 0;
+
+		virtual ~updater() {}
+	};
+
+}