~~
TForm1 *Form1;    int Get_Trace=false;
int x_coor=50;
int y_coor=200;    //---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
        : TForm(Owner)
{    }
//---------------------------------------------------------------------------
void __fastcall TForm1::Button2Click(TObject *Sender)
{
 this->Canvas->MoveTo(50,200);
 this->Canvas->LineTo(600,200);
}
//---------------------------------------------------------------------------
void __fastcall TForm1::FormMouseMove(TObject *Sender, TShiftState Shift,
      int X, int Y)
{
 if (!Get_Trace)
     return;     if (Y<200)
     return;     this->Canvas->MoveTo(x_coor,y_coor);
 this->Canvas->LineTo(X,Y);     x_coor=X;
 y_coor=Y;     Memo1->Lines->Add(IntToStr(X)+"  "+IntToStr(Y));
}
//---------------------------------------------------------------------------
void __fastcall TForm1::FormClick(TObject *Sender)
{
 Get_Trace=!Get_Trace;
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button3Click(TObject *Sender)
{
 TStringList* coor1=new TStringList;
 TStringList* coor2=new TStringList;
 double area=0.;     for (int i=1;iLines->Count;i++) {
      coor1->CommaText=Memo2->Lines->Strings[i-1];
      coor2->CommaText=Memo2->Lines->Strings[i];          double dx=StrToFloat(coor2->Strings[0])-StrToFloat(coor1->Strings[0]);
      area+=dx*(StrToFloat(coor2->Strings[1])+StrToFloat(coor1->Strings[1]));
 }     area/=2;
 delete coor1;
 delete coor2;
 ShowMessage(area);
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button4Click(TObject *Sender)
{
 TStringList* sl=new TStringList;     for (int i=0;iLines->Count;i++) {
      sl->CommaText=Memo1->Lines->Strings[i];
      int x=StrToInt(sl->Strings[0]);
      int y=StrToInt(sl->Strings[1]);          Memo2->Lines->Add(IntToStr(x-50)+" "+IntToStr(y-200));
 }
}
//---------------------------------------------------------------------------