Comment 15 for bug 855839

This has been fixed as of rev. 10672. The cause was slightly different from what I explained above, because it was not simply the bounding box calculation being wrong. In fact the snapping code explicitly try to snap to the clip or mask paths, when available. Now this might be handy in some use cases, but it certainly wasn't very useful here ;-).

So the easy fix was to make snapping to such clipping or mask paths optional, and turn it off by default (I'm guessing not many people will use this feature on a daily basis, but it can cause serious troubles as reported above). You can find a checkbox in the document properties dialog, on the snapping tab. I decided to put it there instead of in the snap toolbar, because IMHO it doesn't deserve such a prominent place in the UI (and screen real estate is too expensive already).

Please test and let me know if it isn't working as expected for some reason.

Thanks for reporting, triaging, debugging, and being patient ;-)