DevExpress.XtraEditors.HtmlContentControl as a text editor

ShittyTextEdit.cs

using DevExpress.XtraEditors;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace DXApplication39 {
    public partial class Form1 : DevExpress.XtraEditors.XtraForm {
        public Form1() {
            InitializeComponent();

            var timer = new Timer();
            timer.Interval = 500;
            timer.Tick += (sender, e) => {
                var style = htmlContentControl1.HtmlTemplate.Styles;
                if (style.Contains("Transparent")) {
                    htmlContentControl1.HtmlTemplate.Styles = style.Replace("Transparent", "Black");
                } else {
                    htmlContentControl1.HtmlTemplate.Styles = style.Replace("Black", "Transparent");
                }
            };
            timer.Start();

            var text = new TextWithCaret() { Text = "SampleText", CaretPosition = 6 };
            htmlContentControl1.DataContext = text;
            htmlContentControl1.KeyDown += (sender, e) => {
                switch (e.KeyCode) {
                    case Keys.Back:
                        text.Backspace();
                        return;
                    case Keys.Delete:
                        text.Delete();
                        return;
                    case Keys.Left:
                        text.CaretPosition--;
                        return;
                    case Keys.Right:
                        text.CaretPosition++;
                        return;
                    case Keys.Enter:
                        text.Insert(Environment.NewLine);
                        return;
                    default:
                        var c = (char)e.KeyValue;
                        if (true || char.IsLetterOrDigit(c))
                            text.Insert(c.ToString());
                        return;
                }
            };
        }
    }

    public class MyHtmlContentControl : HtmlContentControl {
        protected override bool IsInputKey(Keys keyData) {
            if ((keyData & (Keys.Left | Keys.Right)) != 0) return true;
            return base.IsInputKey(keyData);
        }
    }

    public class TextWithCaret : INotifyPropertyChanged {
        private string text;
        private int caretPosition;
        
        public string Text {
            get => text;
            set {
                text = value;
                CaretPosition = caretPosition;
                Update();
            }
        }
        public int CaretPosition {
            get => caretPosition;
            set {
                caretPosition = Math.Max(0, Math.Min(text.Length, value));
                Update();
            }
        }

        public string Left => text.Substring(0, caretPosition);
        public string Right => text.Substring(caretPosition);

        public void Backspace() {
            if (Left.Length == 0) return;
            text = text.Remove(caretPosition - 1, 1);
            caretPosition--;
            Update();
        }

        public void Delete() {
            if (Right.Length == 0) return;
            text = text.Remove(caretPosition, 1);
            Update();
        }

        public void Insert(string s) {
            text = text.Insert(caretPosition, s);
            caretPosition++;
            Update();
        }

        private void Update() {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("Left"));
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("Right"));
        }
        public event PropertyChangedEventHandler PropertyChanged;
    }
}

/*
this.htmlContentControl1.HtmlTemplate.Styles = ".leftsegment{\r\n\tborder-right: 1px solid Black;\r\n\tmin-width: 1px;\r\n}";
this.htmlContentControl1.HtmlTemplate.Template = "<span class=\"leftsegment\">${Left}</span><span class=\"rightsegment\">${Right}</span>";
*/