Title: Transparent text on desktop
Use GetDesktopWindow and GetWindowDC functions to find attributes of desktop for further using. And set background mode by using GetBKMode function.
procedure TForm1.Button1Click(Sender: TObject);
var
Desktop: THandle;
MyCanvas: TCanvas;
DesktopDC: HDC;
begin
Desktop:=GetDesktopWindow;
DesktopDC:=GetWindowDC(Desktop);
MyCanvas:=TCanvas.Create;
MyCanvas.Handle:=DesktopDC;
SetBkMode(MyCanvas.Handle, TRANSPARENT);
MyCanvas.TextOut(10,10, 'Hello');
end;