I've been giving bounding boxes more thought, and it seems like there are actually three different kinds of bounding boxes required in Inkscape:
- GEOMETRIC: the bounding box of the path data, without stroking -- this is what the SVG standard means by "bounding box"; it is not reduced by clipping
- INTERACTION: the bounding box with stroke, plus (maybe) visual things like the filter effects region; it _may_ be reduced by clipping
- VISUAL: the bounding box with stroke, _including miter joins_, and things like the filter effects region, it has to be be reduced by clipping
The idea is that GEOMETRIC will be used to satisfy the SVG specification, while INTERACTION defines the region that a user can "grab on to", and VISUAL defines the region within which e.g. all affected pixels fall.
-mental