Comment 34 for bug 1384915

yes, you're right. Sorry about that, I was focusing so much on the size of the viewbox that I forgot about the possible added transform.
This can be fixed by implementing rev 13776, which effectively avoids a recalculation that is unnecessary.
However, rev 13776 requires that rev 13632 must first be implemented, at least the change involving document.cpp, not the change in units.xml.
And there was an intermediate change, rev 13753, which would also need to be included, since it was a bug introduced by rev 13632.

I can do this, over the next two or three days. I don't have a working copy of the 91x repository, so I'll need to download it for testing purposes. And I don't have the ability to produce diff files that involve more than one file, so I would just submit the original files in their entirety as a zip file after they have been tested.