trail-into-darkness/Packages/com.jovian.inspector/Editor/Attributes/MinMaxRangeAttribute.cs

// ---------------------------------------------------------------------------- 
// Author: Richard Fine
// Source: https://bitbucket.org/richardfine/scriptableobjectdemo
// ----------------------------------------------------------------------------

using System;
using UnityEngine;

namespace InspectorToolkit {
    public class MinMaxRangeAttribute : PropertyAttribute {
        public MinMaxRangeAttribute(float min, float max) {
            Min = min;
            Max = max;
        }

        public readonly float Min;
        public readonly float Max;
    }

    [Serializable]
    public struct RangedFloat {
        public float Min;
        public float Max;

        public RangedFloat(float min, float max) {
            Min = min;
            Max = max;
        }
    }

    [Serializable]
    public struct RangedInt {
        public int Min;
        public int Max;

        public RangedInt(int min, int max) {
            Min = min;
            Max = max;
        }
    }

    public static class RangedExtensions {
        public static float LerpFromRange(this RangedFloat ranged, float t) {
            return Mathf.Lerp(ranged.Min, ranged.Max, t);
        }

        public static float LerpFromRangeUnclamped(this RangedFloat ranged, float t) {
            return Mathf.LerpUnclamped(ranged.Min, ranged.Max, t);
        }

        public static float LerpFromRange(this RangedInt ranged, float t) {
            return Mathf.Lerp(ranged.Min, ranged.Max, t);
        }

        public static float LerpFromRangeUnclamped(this RangedInt ranged, float t) {
            return Mathf.LerpUnclamped(ranged.Min, ranged.Max, t);
        }
    }
}

#if UNITY_EDITOR
namespace InspectorToolkit.Internal {
    using UnityEditor;

    [CustomPropertyDrawer(typeof(MinMaxRangeAttribute))]
    public class MinMaxRangeIntAttributeDrawer : PropertyDrawer {
        public override void OnGUI(Rect position, SerializedProperty property, GUIContent label) {
            SerializedProperty minProp = property.FindPropertyRelative("Min");
            SerializedProperty maxProp = property.FindPropertyRelative("Max");
            if(minProp == null || maxProp == null) {
                Debug.LogWarning("MinMaxRangeAttribute used on <color=brown>" +
                                 property.name +
                                 "</color>. Must be used on types with Min and Max fields",
                    property.serializedObject.targetObject);

                return;
            }

            var minValid = minProp.propertyType == SerializedPropertyType.Integer || minProp.propertyType == SerializedPropertyType.Float;
            var maxValid = maxProp.propertyType == SerializedPropertyType.Integer || maxProp.propertyType == SerializedPropertyType.Float;
            if(!maxValid || !minValid || minProp.propertyType != maxProp.propertyType) {
                Debug.LogWarning("MinMaxRangeAttribute used on <color=brown>" +
                                 property.name +
                                 "</color>. Min and Max fields must be of int or float type",
                    property.serializedObject.targetObject);

                return;
            }

            MinMaxRangeAttribute rangeAttribute = (MinMaxRangeAttribute)attribute;

            label = EditorGUI.BeginProperty(position, label, property);
            position = EditorGUI.PrefixLabel(position, label);

            bool isInt = minProp.propertyType == SerializedPropertyType.Integer;

            float minValue = isInt ? minProp.intValue : minProp.floatValue;
            float maxValue = isInt ? maxProp.intValue : maxProp.floatValue;
            float rangeMin = rangeAttribute.Min;
            float rangeMax = rangeAttribute.Max;


            const float rangeBoundsLabelWidth = 40f;

            var rangeBoundsLabel1Rect = new Rect(position);
            rangeBoundsLabel1Rect.width = rangeBoundsLabelWidth;
            GUI.Label(rangeBoundsLabel1Rect, new GUIContent(minValue.ToString(isInt ? "F0" : "F2")));
            position.xMin += rangeBoundsLabelWidth;

            var rangeBoundsLabel2Rect = new Rect(position);
            rangeBoundsLabel2Rect.xMin = rangeBoundsLabel2Rect.xMax - rangeBoundsLabelWidth;
            GUI.Label(rangeBoundsLabel2Rect, new GUIContent(maxValue.ToString(isInt ? "F0" : "F2")));
            position.xMax -= rangeBoundsLabelWidth;

            EditorGUI.BeginChangeCheck();
            EditorGUI.MinMaxSlider(position, ref minValue, ref maxValue, rangeMin, rangeMax);

            if(EditorGUI.EndChangeCheck()) {
                if(isInt) {
                    minProp.intValue = Mathf.RoundToInt(minValue);
                    maxProp.intValue = Mathf.RoundToInt(maxValue);
                }
                else {
                    minProp.floatValue = minValue;
                    maxProp.floatValue = maxValue;
                }
            }

            EditorGUI.EndProperty();
        }
    }
}
#endif