title: Why is result of DrawLine invisible on iOS?
body: <p>Have a FM HD form.
  on the form: button and image (TImage).</p>
  
  <pre><code>procedure TfrmImageEditor.Button2Click(Sender: TObject);
  begin
    Image.Canvas.Stroke.Color := $ffff0000 ;  // Red
    Image.Canvas.Stroke.Kind := TBrushKind.bkSolid;
    Image.Canvas.StrokeThickness:= 10;
    Image.Canvas.BeginScene;
    Image.Canvas.DrawLine(PointF(0, 0), PointF(100, 100),1);
    Image.Canvas.EndScene;
  end;
  </code></pre>
  
  <p>After I click the button I see a line, excellent red line... but only in Win32.
  When I run the app in iOS simulator or real android I see nothing after clicking the button.</p>
  
  <p>What should I do to see a line on the Image?</p>
  
  <p>UPDATE: Delphi XE5, Windows 7</p>