Автор: http://www.swissdelphicenter.ch

uses
  QT;

procedure TForm1.RotatedText(Cnv: TCanvas; Wkl: Integer;
  Pxy: TPoint; Txt: string);
var
  PrPoint: TPoint;
begin
  // Rotate Canvas
  QPainter_rotate(Cnv.Handle, Wkl);
  // Convert Device Coord. to Modell- Coord.
  QPainter_xFormDev(Cnv.Handle, PPoint(@PrPoint),
    PPoint(@Pxy));
  // Write text.
  Canvas.TextOut(PrPoint.X, PrPoint.Y, 'Txt');
end;