ExpandableAttributeDrawer Unity

ExpandableAttributeDrawer.cs

using UnityEngine;

#if UNITY_EDITOR
using System;
using System.Collections.Generic;
using UnityEditor;
#endif

#if UNITY_EDITOR
/// <summary>
/// Draws the property field for any field marked with ExpandableAttribute.
/// </summary>
[CustomPropertyDrawer(typeof(ExpandableAttribute), true)]
public class ExpandableAttributeDrawer : PropertyDrawer
{
    // Use the following area to change the style of the expandable ScriptableObject drawers;
    #region Style Setup
    private enum BackgroundStyles
    {
        None,
        HelpBox,
        Darken,
        Lighten
    }

    /// <summary>
    /// Whether the default editor Script field should be shown.
    /// </summary>
    private static bool SHOW_SCRIPT_FIELD = false;

    /// <summary>
    /// The spacing on the inside of the background rect.
    /// </summary>
    private static float INNER_SPACING = 6.0f;

    /// <summary>
    /// The spacing on the outside of the background rect.
    /// </summary>
    private static float OUTER_SPACING = 4.0f;

    /// <summary>
    /// The style the background uses.
    /// </summary>
    private static BackgroundStyles BACKGROUND_STYLE = BackgroundStyles.HelpBox;

    /// <summary>
    /// The colour that is used to darken the background.
    /// </summary>
    private static Color DARKEN_COLOUR = new Color(0.0f, 0.0f, 0.0f, 0.2f);

    /// <summary>
    /// The colour that is used to lighten the background.
    /// </summary>
    private static Color LIGHTEN_COLOUR = new Color(1.0f, 1.0f, 1.0f, 0.2f);
    #endregion

    public override float GetPropertyHeight(SerializedProperty property, GUIContent label)
    {
        float totalHeight = 0.0f;

        totalHeight += EditorGUIUtility.singleLineHeight;

        if (property.objectReferenceValue == null)
            return totalHeight;

        if (!property.isExpanded)
            return totalHeight;

        SerializedObject targetObject = new SerializedObject(property.objectReferenceValue);

        if (targetObject == null)
            return totalHeight;

        SerializedProperty field = targetObject.GetIterator();

        field.NextVisible(true);

        if (SHOW_SCRIPT_FIELD)
        {
            totalHeight += EditorGUIUtility.singleLineHeight + EditorGUIUtility.standardVerticalSpacing;
        }

        while (field.NextVisible(false))
        {
            totalHeight += EditorGUI.GetPropertyHeight(field, true) + EditorGUIUtility.standardVerticalSpacing;
        }

        totalHeight += INNER_SPACING * 2;
        totalHeight += OUTER_SPACING * 2;

        return totalHeight;
    }

    public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
    {
        Rect fieldRect = new Rect(position);
        fieldRect.height = EditorGUIUtility.singleLineHeight;

        EditorGUI.PropertyField(fieldRect, property, label, true);

        if (property.objectReferenceValue == null)
            return;

        property.isExpanded = EditorGUI.Foldout(fieldRect, property.isExpanded, GUIContent.none, true);

        if (!property.isExpanded)
            return;

        SerializedObject targetObject = new SerializedObject(property.objectReferenceValue);

        if (targetObject == null)
            return;


        #region Format Field Rects
        List<Rect> propertyRects = new List<Rect>();
        Rect marchingRect = new Rect(fieldRect);

        Rect bodyRect = new Rect(fieldRect);
        bodyRect.xMin += EditorGUI.indentLevel * 14;
        bodyRect.yMin += EditorGUIUtility.singleLineHeight + EditorGUIUtility.standardVerticalSpacing
            + OUTER_SPACING;

        SerializedProperty field = targetObject.GetIterator();
        field.NextVisible(true);

        marchingRect.y += INNER_SPACING + OUTER_SPACING;

        if (SHOW_SCRIPT_FIELD)
        {
            propertyRects.Add(marchingRect);
            marchingRect.y += EditorGUIUtility.singleLineHeight + EditorGUIUtility.standardVerticalSpacing;
        }

        while (field.NextVisible(false))
        {
            marchingRect.y += marchingRect.height + EditorGUIUtility.standardVerticalSpacing;
            marchingRect.height = EditorGUI.GetPropertyHeight(field, true);
            propertyRects.Add(marchingRect);
        }

        marchingRect.y += INNER_SPACING;

        bodyRect.yMax = marchingRect.yMax;
        #endregion

        DrawBackground(bodyRect);

        #region Draw Fields
        EditorGUI.indentLevel++;

        int index = 0;
        field = targetObject.GetIterator();
        field.NextVisible(true);

        if (SHOW_SCRIPT_FIELD)
        {
            //Show the disabled script field
            EditorGUI.BeginDisabledGroup(true);
            EditorGUI.PropertyField(propertyRects[index], field, true);
            EditorGUI.EndDisabledGroup();
            index++;
        }

        //Replacement for "editor.OnInspectorGUI ();" so we have more control on how we draw the editor
        while (field.NextVisible(false))
        {
            try
            {
                EditorGUI.PropertyField(propertyRects[index], field, true);
            }
            catch (StackOverflowException)
            {
                field.objectReferenceValue = null;
                Debug.LogError("Detected self-nesting cauisng a StackOverflowException, avoid using the same " +
                    "object iside a nested structure.");
            }

            index++;
        }

        targetObject.ApplyModifiedProperties();

        EditorGUI.indentLevel--;
        #endregion
    }

    /// <summary>
    /// Draws the Background
    /// </summary>
    /// <param name="rect">The Rect where the background is drawn.</param>
    private void DrawBackground(Rect rect)
    {
        switch (BACKGROUND_STYLE)
        {

            case BackgroundStyles.HelpBox:
                EditorGUI.HelpBox(rect, "", MessageType.None);
                break;

            case BackgroundStyles.Darken:
                EditorGUI.DrawRect(rect, DARKEN_COLOUR);
                break;

            case BackgroundStyles.Lighten:
                EditorGUI.DrawRect(rect, LIGHTEN_COLOUR);
                break;
        }
    }
}
#endif