Automatic centering and positioning

Hi all

I have spent a bit of time on Stack Overflow lately, answering questions on
SVG.  It seems a very common use case that people want to centre elements
inside other elements.  For example, text in a circle, image in a box.

I have been wondering if this use case has been discussed before and
whether there were any previous proposals or interest in adding some sort
of feature that can automatically position elements with respect to a box
or other element.

Obviously you can achieve some control with child <svg>s and the text
baseline properties, but these can be hard to use and can require manual
tweaking.  Something automatic would be nice.

I had an idea or two about how you could do this, but wanted to check
whether other people agree it would be desirable (or not).

Paul