Line index in Richedit

[Gutelo]

Meine Loesung Zum Zentrieren der Selection-Line im Richedit:

Delphi-Quellcode:

procedure TForm.Button1Click(Sender: TObject);
const
  EM_EXLINEFROMCHAR = WM_USER + 54;
var FirstLine, LastLine, SelLine : Integer;
    LinesToScroll : Integer;
    r: TRect;
    i: Integer;
begin
 // Get selection line
  SelLine := Richedit1.caretpos.y;
 // Get first visible line
  FirstLine := RichEdit1.Perform(EM_GETFIRSTVISIBLELINE, 0, 0);
 // Get last visible line
  RichEdit1.Perform(EM_GETRECT, 0, Longint(@r));
  r.Left := r.Left + 1;
  r.Top := r.Bottom - 2;
  i := RichEdit1.Perform(EM_CHARFROMPOS, 0, Integer(@r.topleft));
  LastLine := RichEdit1.Perform(EM_EXLINEFROMCHAR, 0, i);
 // Center selection in Richedit by scrolling
  LinesToScroll := -Round(0.5*(LastLine+FirstLine) - SelLine);
  RichEdit1.Perform(EM_LINESCROLL, 0, LinesToScroll);
end;