Adds a frequency or period custom drawer to Unity. Because I can never remember which one I've used.

FrequencyOrPeriod.cs

/*
  Adds a frequency or period custom drawer to Unity because I can never
  remember which one I've used.  See here for a quick demonstration:
  https://twitter.com/shanecelis/status/989234269020180480

  Its licensed under the MIT License.

 * * *

  Copyright 2018 Shane Celis

  Permission is hereby granted, free of charge, to any person obtaining a copy of
  this software and associated documentation files (the "Software"), to deal in
  the Software without restriction, including without limitation the rights to
  use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
  the Software, and to permit persons to whom the Software is furnished to do so,
  subject to the following conditions:

  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
  FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
  COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
  IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
using UnityEngine;
#if UNITY_EDITOR
using UnityEditor;
#endif

[System.Serializable]
public class FrequencyOrPeriod {

  public enum Kind {
    Frequency,
    Period
  }

  public Kind kind = Kind.Frequency;

  [SerializeField]
  private float _frequency = 1f;

  public float frequency {
    get { return _frequency; }
    set { _frequency = value; }
  }
  public float period {
    get { return 1f / _frequency; }
    set { _frequency = 1f / value; }
  }

  public float Value {
    get { return kind == Kind.Frequency ? frequency : period; }
    set {
      if (kind == Kind.Frequency)
        frequency = value;
      else
        period = value;
    }
  }

  public static FrequencyOrPeriod Frequency(float f) {
    return new FrequencyOrPeriod { _frequency = f, kind = Kind.Frequency };
  }

  public static FrequencyOrPeriod Period(float p) {
    return new FrequencyOrPeriod { _frequency = 1f / p, kind = Kind.Period };
  }

  public bool isFrequency {
    get { return kind == Kind.Frequency; }
  }
}

#if UNITY_EDITOR
[CustomPropertyDrawer (typeof (FrequencyOrPeriod))]
class FrequencyOrPeriodDrawer : PropertyDrawer {

  // Draw the property inside the given rect
  public override void OnGUI (Rect position, SerializedProperty property, GUIContent label) {
    // Using BeginProperty / EndProperty on the parent property means that
    // prefab override logic works on the entire property.

    EditorGUI.BeginProperty (position, label, property);
    float frequency = property.FindPropertyRelative("_frequency").floatValue;
    var kind = (FrequencyOrPeriod.Kind) property.FindPropertyRelative("kind").intValue;
    // label = new GUIContent(label);
    var freq = new FrequencyOrPeriod { frequency = frequency, kind = kind };
    float amount = freq.Value;


    // Draw label
    position = EditorGUI.PrefixLabel (position, GUIUtility.GetControlID (FocusType.Passive), label);

    // Don't make child fields be indented
    var indent = EditorGUI.indentLevel;
    EditorGUI.indentLevel = 0;


    GUIContent suffixContent;
    if (! Mathf.Approximately(amount, 1f))
      suffixContent = new GUIContent(freq.isFrequency ? " cycles per second" : " seconds per cycle");
    else
      suffixContent = new GUIContent(freq.isFrequency ? " cycle per second" : " second per cycle");
    Vector2 suffixSize = GUI.skin.label.CalcSize(suffixContent);
    var buttonWidth = GUI.skin.button.CalcSize(new GUIContent("Frequency")).x;
    // Calculate rects
    var padding = 2f;
    var width = (position.width - suffixSize.x - buttonWidth - 2 * padding);
    Rect buttonRect = new Rect (position.x, position.y, buttonWidth, position.height);
    Rect amountRect = new Rect (position.x + buttonWidth + padding, position.y, width, position.height);
    Rect suffixRect = new Rect (position.x + buttonWidth + width + 2 * padding, position.y, suffixSize.x, position.height);
    var floatStyle = new GUIStyle(GUI.skin.textField);
    floatStyle.alignment = TextAnchor.MiddleRight;
    float newAmount = EditorGUI.FloatField(amountRect, amount, floatStyle);
    if (newAmount != amount) {
      switch (kind) {
        case FrequencyOrPeriod.Kind.Frequency:
          property.FindPropertyRelative("_frequency").floatValue = newAmount;
          break;
        case FrequencyOrPeriod.Kind.Period:
          property.FindPropertyRelative("_frequency").floatValue = 1f / newAmount;
          break;
        default:
          throw new System.Exception("Unexpected value for kind " + kind);
      }
    }
    EditorGUI.LabelField(suffixRect, suffixContent);
    var newKind = (FrequencyOrPeriod.Kind) EditorGUI.EnumPopup(buttonRect, kind);
    if (newKind != kind) {
      property.FindPropertyRelative("kind").intValue = (int) newKind;
    }

    // Set indent back to what it was
    EditorGUI.indentLevel = indent;

    EditorGUI.EndProperty ();
  }
}
#endif