Change font with javascript on mobile version

I have tried several ways to change font with javascript but it is not working immediate on mobile version.

On desktop it is perfectly fine.

I call the following method on document, page and form level:
this.getField(<fieldname>).textFont=<font>;

Did I get soemthing wrong or is it a bug in mobile version. 

I have attached a simple test form with font selection and a load button for the three XML levels.

As well I have attached a saved file. If I open the file on desktiop and save. The Fields formatted on document and form level work, but the live changes with the selection won't.

To get the font selection working would be my goal.