Tri-Inspector/Editor/Elements/TriBoxGroupElement.cs

using TriInspector.Utilities;
using UnityEditor;
using UnityEngine;

namespace TriInspector.Elements
{
    public class TriBoxGroupElement : TriPropertyCollectionBaseElement
    {
        private const float HeaderWidth = 22;
        private const float InsetTop = 4;
        private const float InsetBottom = 4;
        private const float InsetLeft = 4;
        private const float InsetRight = 4;

        private readonly GUIContent _headerLabel;

        public TriBoxGroupElement(DeclareBoxGroupAttribute attribute)
        {
            _headerLabel = attribute.Title == null
                ? GUIContent.none
                : new GUIContent(attribute.Title);
        }

        public override float GetHeight(float width)
        {
            var height = base.GetHeight(width) + InsetTop + InsetBottom;

            if (_headerLabel != GUIContent.none)
            {
                height += HeaderWidth;
            }

            return height;
        }

        public override void OnGUI(Rect position)
        {
            var headerBgRect = new Rect(position)
            {
                height = _headerLabel != GUIContent.none ? HeaderWidth : 0,
            };
            var headerLabelRect = new Rect(headerBgRect)
            {
                xMin = headerBgRect.xMin + 6,
                xMax = headerBgRect.xMax - 6,
                yMin = headerBgRect.yMin + 2,
                yMax = headerBgRect.yMax - 2,
            };
            var contentBgRect = new Rect(position)
            {
                yMin = headerBgRect.yMax,
            };
            var contentRect = new Rect(contentBgRect)
            {
                xMin = contentBgRect.xMin + InsetLeft,
                xMax = contentBgRect.xMax - InsetRight,
                yMin = contentBgRect.yMin + InsetTop,
                yMax = contentBgRect.yMax - InsetBottom,
            };

            if (_headerLabel != GUIContent.none)
            {
                TriEditorGUI.DrawBox(headerBgRect, TriEditorStyles.HeaderBox);
                EditorGUI.LabelField(headerLabelRect, _headerLabel);
                TriEditorGUI.DrawBox(contentBgRect, TriEditorStyles.ContentBox);
            }
            else
            {
                TriEditorGUI.DrawBox(contentBgRect, TriEditorStyles.Box);
            }

            using (TriGuiHelper.PushLabelWidth(EditorGUIUtility.labelWidth - InsetLeft))
            {
                base.OnGUI(contentRect);
            }
        }
    }
}