netch/Netch/Forms/SyncGlobalCheckBox.cs

using System;
using System.Drawing;
using System.Windows.Forms;

namespace Netch.Forms
{
    public class SyncGlobalCheckBox : CheckBox
    {
        public SyncGlobalCheckBox()
        {
            AutoCheck = false;
            OnSyncGlobalChanged();
        }

        private bool _syncGlobal;

        private bool _globalValue;

        public bool SyncGlobal
        {
            get => _syncGlobal;
            set
            {
                if (value == _syncGlobal)
                    return;

                _syncGlobal = value;

                OnSyncGlobalChanged();
            }
        }

        public bool GlobalValue
        {
            get => _globalValue;
            set
            {
                if (value == _globalValue)
                    return;

                _globalValue = value;

                if (SyncGlobal)
                    Checked = value;
            }
        }

        protected override void OnClick(EventArgs e)
        {
            if (Checked == GlobalValue)
            {
                SyncGlobal = !SyncGlobal;
                if (SyncGlobal)
                    return;
            }

            Checked = !Checked;
            base.OnClick(e);
        }

        public bool? Value
        {
            get => _syncGlobal ? null : Checked;
            set
            {
                if (value == null)
                {
                    SyncGlobal = true;
                }
                else
                {
                    SyncGlobal = false;
                    Checked = (bool)value;
                }
            }
        }

        private void OnSyncGlobalChanged()
        {
            if (_syncGlobal)
            {
                Font = new Font(Font, FontStyle.Regular);
                BackColor = SystemColors.Control;
            }
            else
            {
                Font = new Font(Font, FontStyle.Bold | FontStyle.Italic);
                BackColor = Color.Yellow;
            }
        }
    }
}