フィレットTextBoxテキストボックスの描画

public class TextBoxCu : Control {
    public TextBoxCu() {
        this.SetStyle(ControlStyles.UserPaint, true);
        this.SetStyle(ControlStyles.ResizeRedraw, true);
        this.SetStyle(ControlStyles.AllPaintingInWmPaint, true);
        this.SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
        this.SetStyle(ControlStyles.SupportsTransparentBackColor, true);
 
        m_tbx = new TextBox();
        m_tbx.Multiline = true;
        m_tbx.BorderStyle = BorderStyle.None;
        this.BackColor = Color.Transparent;
        m_tbx.GotFocus += (s, e) => { m_bFocus = true; this.Invalidate(); };
        m_tbx.LostFocus += (s, e) => { m_bFocus = false; this.Invalidate(); };
        m_tbx.KeyDown += (s, e) => this.OnKeyDown(e);
        m_tbx.KeyPress += (s, e) => this.OnKeyPress(e);
        m_tbx.KeyUp += (s, e) => this.OnKeyUp(e);
        m_tbx.TextChanged += (s, e) => this.OnTextChanged(e);
        m_tbx.BackColorChanged += (s, e) => m_tbx.BackColor = Color.White;
        this.Controls.Add(m_tbx);
    }
 
    public override string Text {
        get { return m_tbx.Text; }
        set {
            if (m_tbx.Text == value) return;
            m_tbx.Text = value;
        }
    }
 
    public TextBox TextBox {
        get { return m_tbx; }
    }
 
    public override Color BackColor {
        get { return Color.Transparent; }
        set { }
    }
 
    public override Color ForeColor {
        get { return base.ForeColor; }
        set {
            if (base.ForeColor == value) return;
            base.ForeColor = value;
            m_tbx.ForeColor = value;
        }
    }
 
    private bool _ReadOnly;
 
    public bool ReadOnly {
        get { return m_tbx.ReadOnly; }
        set { m_tbx.ReadOnly = value; m_tbx.BackColor = Color.White; }
    }
 
    private TextBox m_tbx;
    private bool m_bFocus;
 
    public event EventHandler TextChanged;
 
    protected virtual void OnTextChanged(EventArgs e) {
        if (this.TextChanged != null) this.TextChanged(this, e);
    }
 
    protected override void OnResize(EventArgs e) {
        m_tbx.Left = m_tbx.Top = 3;
        m_tbx.Width = this.Width - 6;
        m_tbx.Height = this.Height - 6;
        base.OnResize(e);
    }
 
    protected override void OnPaint(PaintEventArgs e) {
        Graphics g = e.Graphics;
        g.SmoothingMode = SmoothingMode.HighQuality;
        using (SolidBrush sb = new SolidBrush(Color.White)) {
            g.FillPath(
                sb,
                RenderHelper.CreateRoundedRectanglePath(new Rectangle(0, 0, this.Width - 1, this.Height - 1), 5)
                );
        }
        using (LinearGradientBrush lgb = new LinearGradientBrush(
           new Point(0, 1), new Point(0, this.Height),
           Color.LightGray, Color.White)) {
            g.DrawPath(
                new Pen(lgb),
                RenderHelper.CreateRoundedRectanglePath(new Rectangle(0, 1, this.Width - 1, this.Height - 2), 5)
                );
        }
        using (LinearGradientBrush lgb = new LinearGradientBrush(
           new Point(0, 0), new Point(0, this.Height - 1),
           m_bFocus ? Color.DodgerBlue : Color.Gray, Color.FromArgb(20, 0, 0, 0))) {
            g.DrawPath(
                new Pen(lgb),
                RenderHelper.CreateRoundedRectanglePath(new Rectangle(0, 0, this.Width - 1, this.Height - 2), 5)
                );
        }
        base.OnPaint(e);
    }
}