smart-mobile-studio - How to get the height and width of the visible browser area

Question

How can I retrieve the height and width of the browser area?

I want to show one form always in landscape mode, regardless whether the mobile phone has rotated the browser view.

if the browser is in portrait postion I want to rotate the form (TForm.Angel := 90). In order to force landscape mode.

Update:
Here is a picture, how the result should look like:

I found a solution, but I am not so really happy with it. It's easy to rotate the view, but the origin is not in the center, so I have to manually correct it, and I don't understand why this transformation is neccessary.
Here is the code:

procedure TForm1.ForceLandscape(aEnabled: Boolean);
var
  browserWidth, browserHeight: Integer;
  isLandscapeMode: Boolean;
begin
  browserHeight := Application.Display.ClientHeight;  //BrowserAPI.Window.innerHeight;
  browserWidth := Application.Display.ClientWidth;    //BrowserAPI.Window.innerWidth;

  isLandscapeMode := browserHeight > browserWidth;

  if aEnabled and isLandscapeMode then
  begin
    Angle := 90;

    Height := browserWidth;
    Width := browserHeight;
  end
  else
  begin
    Angle := 0;

    Height := browserHeight;
    Width := browserWidth;
  end;
end;

procedure TForm1.InitializeForm;
begin
  inherited;
  // this is a good place to initialize components

  //Need to put a transform.orign for form rotation (Angle)
  var x := trunc(Application.Display.ClientWidth / 2);
  var myStyle := TInteger.ToPxStr(x) + ' ' + TInteger.ToPxStr(x);
  w3_setStyle(Handle, w3_CSSPrefix('TransformOrigin'), myStyle);

end;