ml-agents/unity-environment/Assets/ML-Agents/Editor/ResetParameterDrawer.cs

using UnityEngine;
using UnityEditor;
using System;
using System.Linq;
using UnityEditor.SceneManagement;

[CustomPropertyDrawer(typeof(ResetParameters))]
public class ResetParameterDrawer : PropertyDrawer
{
    private ResetParameters _Dictionary;
    private const float lineHeight = 17f;

    public override float GetPropertyHeight(SerializedProperty property, GUIContent label)
    {
        CheckInitialize(property, label);
        return (_Dictionary.Count + 2) * lineHeight;
    }

    public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
    {

        CheckInitialize(property, label);
        position.height = lineHeight;
        EditorGUI.LabelField(position, label);

        EditorGUI.BeginProperty(position, label, property);
        foreach (var item in _Dictionary)
        {
            var key = item.Key;
            var value = item.Value;
            position.y += lineHeight;

            // This is the rectangle for the key
            var keyRect = position;
            keyRect.x += 20;
            keyRect.width /= 2;
            keyRect.width -= 24;
            EditorGUI.BeginChangeCheck();
            var newKey = EditorGUI.TextField(keyRect, key);
            if (EditorGUI.EndChangeCheck())
            {
                EditorSceneManager.MarkSceneDirty(EditorSceneManager.GetActiveScene());
                try
                {
                    _Dictionary.Remove(key);
                    _Dictionary.Add(newKey, value);
                }
                catch (Exception e)
                {
                    Debug.Log(e.Message);
                }
                break;
            }

            // This is the Rectangle for the value
            var valueRect = position;
            valueRect.x = position.width / 2 + 15;
            valueRect.width = keyRect.width - 18;
            EditorGUI.BeginChangeCheck();
            value = EditorGUI.FloatField(valueRect, value);
            if (EditorGUI.EndChangeCheck())
            {
                EditorSceneManager.MarkSceneDirty(EditorSceneManager.GetActiveScene());
                _Dictionary[key] = value;
                break;
            }
        }

        // This is the rectangle for the Add button
        position.y += lineHeight;
        var AddButtonRect = position;
        AddButtonRect.x += 20;
        AddButtonRect.width /= 2;
        AddButtonRect.width -= 24;
        if (GUI.Button(AddButtonRect, new GUIContent("Add New",
                  "Add a new item to the default reset paramters"), EditorStyles.miniButton))
        {
            EditorSceneManager.MarkSceneDirty(EditorSceneManager.GetActiveScene());
            AddNewItem();
        }

        // This is the rectangle for the Remove button
        var RemoveButtonRect = position;
        RemoveButtonRect.x = position.width / 2 + 15;
        RemoveButtonRect.width = AddButtonRect.width - 18;
        if (GUI.Button(RemoveButtonRect, new GUIContent("Remove Last",
                 "Remove the last item to the default reset paramters"), EditorStyles.miniButton))
        {
            EditorSceneManager.MarkSceneDirty(EditorSceneManager.GetActiveScene());
            RemoveLastItem();
        }


        EditorGUI.EndProperty();

    }

    private void CheckInitialize(SerializedProperty property, GUIContent label)
    {
        if (_Dictionary == null)
        {
            var target = property.serializedObject.targetObject;
            _Dictionary = fieldInfo.GetValue(target) as ResetParameters;
            if (_Dictionary == null)
            {
                _Dictionary = new ResetParameters();
                fieldInfo.SetValue(target, _Dictionary);
            }
        }
    }

    private void ClearResetParamters()
    {
        _Dictionary.Clear();
    }

    private void RemoveLastItem()
    {
        if (_Dictionary.Count > 0)
        {
            string key = _Dictionary.Keys.ToList()[_Dictionary.Count - 1];
            _Dictionary.Remove(key);
        }
    }

    private void AddNewItem()
    {
        string key = "Param-" + _Dictionary.Count.ToString();
        var value = default(float);
        try
        {
            _Dictionary.Add(key, value);
        }
        catch (Exception e)
        {
            Debug.Log(e.Message);
        }
    }
}