[Delphi] Graph Calculator (Linux)

unit Unit1; 
 {
 Copyright by Telefonzelle, 2007
 }
{$mode objfpc}{$H+}

interface

uses
 Classes, SysUtils, LResources, Forms, Controls, Graphics, Dialogs, ExtCtrls,
 Buttons, StdCtrls, ComCtrls, Menus;

type

 { TForm1 }

 TForm1 = class(TForm)
 Button1: TButton;
 Button2: TButton;
 Button3: TButton;
 ComboBox1: TComboBox;
 Edit1: TEdit;
 Edit2: TEdit;
 Edit3: TEdit;
 Edit4: TEdit;
 Label1: TLabel;
 Label2: TLabel;
 Label3: TLabel;
 Label4: TLabel;
 Label5: TLabel;
 Label6: TLabel;
 Shape1: TShape;
 procedure Button1Click(Sender: TObject);
 procedure Button2Click(Sender: TObject);
 procedure Button3Click(Sender: TObject);
 procedure Calculate(Sender: TObject);
 private
 { private declarations }
 public
 { public declarations }
 end; 

var
 Form1: TForm1;
 drawn:boolean;
 a,b,c,d:real;
 y:double;
 funct,x: integer;


implementation

{ TForm1 }


procedure TForm1.Button1Click(Sender: TObject);
begin

 // Ursprung:
 // 180 | 130
 Shape1.Canvas.MoveTo(180,10);
 Shape1.Canvas.LineTo(180,235);
 Shape1.Canvas.MoveTo(10,130);
 Shape1.Canvas.LineTo(350,130);
 drawn:=true;
 Button1.Enabled:=false;
 Button2.Enabled:=true;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
 try
 funct := ComboBox1.ItemIndex;
 a:= StrToFloat(Edit1.Text);
 b:= StrToFloat(Edit2.Text);
 if(funct > 1) then begin
 c:= StrToFloat(Edit4.Text);
 d:= StrToFloat(Edit3.Text);
 end;
 if(funct < 0) then begin
 Showmessage('You have to choose a valid function!');
 end
 else begin
 Calculate(Form1);
 end;
 except
 Showmessage('Invalid data. A, B, C and D are only allowed to be floats. If you dont need some of those variables, just leave them empty.');
 end;
end;

function calcY(i:integer):double;
begin
 if(funct = 0) then begin
 y := 130 - (i*a) - b;
 end;
 if(funct = 1) then begin
 // x² + ax + b
 y := 130 - ((i*i) + (i*a) + (b));
 end;
 if(funct = 2) then begin
 // ax^3 + bx^2 + cx + d
 y := 130 - ((a * (i*i*i)) + (b* (i*i)) + (c*i) + d);
 end;
 result:=y;
end;

procedure TForm1.Calculate(Sender: TObject);
var y2,i:integer;
begin
 Shape1.Canvas.MoveTo(180,Trunc(calcY(0)));
 x := 180;
 y := 130;
 Button1.Enabled:=false;
 Button2.Enabled:=false;
 Button3.Enabled:=false;
 i:=0;

 // Negative i (x) Zahlen, weil ich das irgendwie nicht beides in eine Schleife bringen konnte.. :D
 while(y > 0) and (x < 340) and (x > 0) and ( y < 256) do begin
 Application.ProcessMessages;
 y := calcY(i);
 y2 := strtoint(floattostr(y));
 Shape1.Canvas.LineTo(x,y2);
 sleep(20);
 Label1.Caption := 'X: '+inttostr(i)+' Y: '+floattostr(y2);
 x:=x-10;
 i:=i-1;
 end;

 i:=0;
 Shape1.Canvas.MoveTo(180,Trunc(calcY(0)));
 x := 180;
 y := 130;

// Positive Schleife...
 
 while(y > 0) and (x < 340) and (x > 0) and ( y < 256) do begin
 Application.ProcessMessages;
 y := calcY(i);
 y2 := strtoint(floattostr(y));
 Shape1.Canvas.LineTo(x,y2);
 sleep(20);
 Label1.Caption := 'X: '+inttostr(i)+' Y: '+floattostr(y2);
 x:=x+10;
 i:=i+1;
 end;
 Button3.Enabled:=true;
end;



procedure TForm1.Button3Click(Sender: TObject);
begin
 Shape1.Canvas.Clear;
 drawn:=false;
 Button1.Enabled:=true;
 Shape1.Canvas.MoveTo(0,0);
 Shape1.Canvas.LineTo(0,255);
 Shape1.Canvas.LineTo(367,255);
 Shape1.Canvas.LineTo(367,0);
 Shape1.Canvas.LineTo(0,0);
end;

initialization
 {$I unit1.lrs}
end.