FastColoredTextBoxNS.DocumentMap.OnPaint C# (CSharp) Method

        protected override void OnPaint(PaintEventArgs e)
        {
            if (target == null)
                return;

            var zoom = Scale*100/target.Zoom;

            if (zoom <= float.Epsilon)
                return;

            //calc startPlace
            var r = target.VisibleRange;
            if (startPlace.iLine > r.Start.iLine)
                startPlace.iLine = r.Start.iLine;
            else
            {
                var endP = target.PlaceToPoint(r.End);
                endP.Offset(0, -(int) (ClientSize.Height/zoom) + target.CharHeight);
                var pp = target.PointToPlace(endP);
                if (pp.iLine > startPlace.iLine)
                    startPlace.iLine = pp.iLine;
            }
            startPlace.iChar = 0;
            //calc scroll pos
            var linesCount = target.Lines.Count;
            var sp1 = (float) r.Start.iLine/linesCount;
            var sp2 = (float) r.End.iLine/linesCount;

            //scale graphics
            e.Graphics.ScaleTransform(zoom, zoom);
            //draw text
            var size = new SizeF(ClientSize.Width/zoom, ClientSize.Height/zoom);
            target.DrawText(e.Graphics, startPlace, size.ToSize());

            //draw visible rect
            var p0 = target.PlaceToPoint(startPlace);
            var p1 = target.PlaceToPoint(r.Start);
            var p2 = target.PlaceToPoint(r.End);
            var y1 = p1.Y - p0.Y;
            var y2 = p2.Y + target.CharHeight - p0.Y;

            e.Graphics.SmoothingMode = SmoothingMode.HighQuality;

            using (var brush = new SolidBrush(Color.FromArgb(50, ForeColor)))
            using (var pen = new Pen(brush, 1/zoom))
            {
                var rect = new Rectangle(0, y1, (int) ((ClientSize.Width - 1)/zoom), y2 - y1);
                e.Graphics.FillRectangle(brush, rect);
                e.Graphics.DrawRectangle(pen, rect);
            }

            //draw scrollbar
            if (scrollbarVisible)
            {
                e.Graphics.ResetTransform();
                e.Graphics.SmoothingMode = SmoothingMode.None;

                using (var brush = new SolidBrush(Color.FromArgb(200, ForeColor)))
                {
                    var rect = new RectangleF(ClientSize.Width - 3, ClientSize.Height*sp1, 2,
                        ClientSize.Height*(sp2 - sp1));
                    e.Graphics.FillRectangle(brush, rect);
                }
            }

            needRepaint = false;
        }