unit main;

{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, FileUtil, TAGraph, TAFuncSeries, TASeries, TATools, Forms,
  Controls, Graphics, Dialogs, Types, TAChartUtils;

type

  { TForm1 }

  TForm1 = class(TForm)
    Chart1: TChart;
    Chart1ConstantLine1: TConstantLine;
    Chart1ConstantLine2: TConstantLine;
    Chart1FuncSeries1: TFuncSeries;
    Chart1FuncSeries2: TFuncSeries;
    procedure Chart1ExtentValidate(ASender: TChart;
      var ALogicalExtent: TDoubleRect; var AllowChange: Boolean);
    procedure Chart1FuncSeries1Calculate(const AX: Double; out AY: Double);
    procedure Chart1FuncSeries2Calculate(const AX: Double; out AY: Double);
    procedure FormCreate(Sender: TObject);
  private
    procedure UpdateDomainExclusions;
  end;

var
  Form1: TForm1;

implementation

{$R *.lfm}

uses
  Math;

{ TForm1 }

{ In old Lazarus versions you can update the domain exclusions to a new extent
  in the OnAfterDrawBackWall event. In Laz 2.1 or later, you can use the event
  OnExtentValidate instead - its name is a bit more intuitive... }
(*
procedure TForm1.Chart1AfterDrawBackWall(ASender: TChart; ACanvas: TCanvas;
  const ARect: TRect);
begin
  Unused(ASender, ACanvas, ARect);
  UpdateDomainExclusions;
end;
*)

procedure TForm1.Chart1ExtentValidate(ASender: TChart;
  var ALogicalExtent: TDoubleRect; var AllowChange: Boolean);
begin
  Unused(ASender, ALogicalExtent, AllowChange);
  UpdateDomainExclusions;
end;

procedure TForm1.Chart1FuncSeries1Calculate(const AX: Double; out AY: Double);
begin
  AY := tan(AX);
end;

procedure TForm1.Chart1FuncSeries2Calculate(const AX: Double; out AY: Double);
begin
  AY := ln(AX);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  with Chart1FuncSeries2.DomainExclusions do begin
    AddRange(NegInfinity, 0.0);
  end;
end;

procedure TForm1.UpdateDomainExclusions;
var
  ex: TDoubleRect;
  x: Integer;
begin
  ex := Chart1.CurrentExtent;
  Chart1.DisableRedrawing;
  try
    with Chart1FuncSeries1.DomainExclusions do begin
      Clear;
      for x := Floor(ex.a.x / Pi - 0.5) to Ceil(ex.b.x / Pi + 0.5) do
        AddPoint((x + 0.5) * Pi);
    end;
  finally
    Chart1.EnableRedrawing;
  end;
end;

end.