trigger MapMode ScaleX change in writer

[Caolán McNamara]

On Fri, 2022-05-27 at 09:02 +0800, Mark Hung wrote:
> Now I can make both bPrt and bStretch true, if I ... insert some code
> in  PrintOrPDFExport to set ScaleX and ScaleY ... Interestingly, I
> didn't find any place it is set for the printer. 
> I wonder if it is something that is no longer useful. In that case,
> we may remove the code completely.

I don't really know. I'd check the case of inserting a comment into the
document, then printing with the print dialog "comment: Place in
margins" option enabled. That does some sort of scaling to squeeze the
comments into the print output, but I don't know if it has anything to
do with this particular ScaleX/Y. Likewise the "Pages per sheet" I
don't immediately know if that scaling is done by anything related to
this case, or a separate post processing step.