Steema Central

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uses Series, TeeTools, TeCanvas;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Chart1.View3D:=false;
  Chart1.Legend.Visible:=false;

  Chart1.AddSeries(TFastLineSeries).FillSampleValues;

  with Chart1.Tools.Add(TColorBandTool) as TColorBandTool do
  begin
    Axis:=Chart1.Axes.Bottom;
    StartValue:=10;
    EndValue:=15;
    Transparency:=50;
    Color:=clGray;
  end;
end;

procedure TForm1.Chart1AfterDraw(Sender: TObject);
var StartX, EndX, PosY: Integer;
begin
  with Chart1[0].YValues do
    PosY:=Chart1.Axes.Left.CalcPosValue(MinValue + (MaxValue-MinValue)*2/3);

  with Chart1.Axes.Bottom, (Chart1.Tools[0] as TColorBandTool) do
  begin
    StartX:=CalcPosValue(StartValue);
    EndX:=CalcPosValue(EndValue);
  end;

  with Chart1.Canvas do
  begin
    Pen.Color:=clRed;
    Line(StartX, PosY, EndX, PosY);
  end;
end;