private void newToolStripMenuItem_Click(object sender, EventArgs e)
        {
            int   previousThickness = LinesDoc.Thickness;
            Color previousColor     = LinesDoc.Color;

            LinesDoc           = new LinesDoc(this.Width, this.Height);
            LinesDoc.Thickness = previousThickness;
            LinesDoc.Color     = previousColor;

            lblColor.Text = $"{LinesDoc.Color}";
            lblLines.Text = $"Lines: {LinesDoc.GetLinesNumber()}";
            Invalidate();
        }
 private void Form1_Load(object sender, EventArgs e)
 {
     LinesDoc      = new LinesDoc(this.Width, this.Height);
     lblColor.Text = $"{LinesDoc.Color}";
     lblLines.Text = $"Lines: {LinesDoc.GetLinesNumber()}";
 }