Bug 1591

Created attachment 631 [details]
usercontrol screenshot

This appears to be an issue with WinForms GDI+, and is not specific to TeeChart. To see this issue in action independently of TeeChart, please use the code for the usercontrol below:

  public partial class UserControl1 : UserControl
  {
    public UserControl1()
    {
      InitializeComponent();

      XValues = new List<int>();
      YValues = new List<int>();
      MarginBottom = 0;
    }
    public List<int> XValues { get; set; }
    public List<int> YValues { get; set; }
    public int MarginBottom { get; set; }
    private int CalcXPos(int xValue)
    {
      double range = XValues.Max() - XValues.Min();
      double ratio = rect.Width / range;
      return(int)Math.Round(ratio * (xValue - XValues.Min()));
    }
    private int CalcYPos(int yValue)
    {
      double range = YValues.Max() - YValues.Min();
      int height = rect.Height - MarginBottom;
      double ratio = height / range;
      return height - (int)Math.Round(ratio * (yValue - YValues.Min()));
    }

    private Rectangle rect;
    protected override void OnPaint(PaintEventArgs e)
    {
      rect = e.ClipRectangle;
      Graphics g = e.Graphics;
      g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

      g.FillRectangle(Brushes.Yellow, rect);

      for (int i = 0; i < XValues.Count; i++)
      {
        Point p0 = Point.Empty;
        Point p1 = new Point(CalcXPos(XValues[i]), CalcYPos(YValues[i]));
        if(i > 0)
        {
          p0 = new Point(CalcXPos(XValues[i - 1]), CalcYPos(YValues[i - 1]));

          Pen pen = new Pen(Color.Red, 2.0f);
          g.DrawLine(pen, p0, p1);
        }
      }
    }
  }

this usercontrol can be hosted in a WinForm like this:

    public Form2()
    {
      InitializeComponent();

      this.Width = 750;
      this.Height = 550;

      UserControl1 control1 = new UserControl1();
      control1.Dock = DockStyle.Fill;
      this.Controls.Add(control1);

      int[] xValues = new int[11];
      for (int i = 0; i < 11; i++)
        xValues[i] = 36951 + i * 360;
      int[] yValues = new int[] { 873, 871, 869, 867, 865, 863, 861, 859, 857, 853, 851 };

      control1.XValues.AddRange(xValues);
      control1.YValues.AddRange(yValues);
      control1.MarginBottom = this.Height - 75;
    }

the result can be seen in the image attached, "usercontrol screenshot".