On Thu, 2014-09-18 at 09:50 -0700, mathog wrote:
After some consideration it seems to me that the viewbox coordinates should come out to 96dpi no matter what the physical length units are.
I am sympathetic to this view and that was my initial thinking before discussing it inside the SVG working group. It certainly has the advantage that the use of absolute units ('in', 'cm',) inside the SVG works as naively expected. But there are two disadvantages:
1. To get exact metric values of length you must include units such as '2mm'. We would need to add this ability to Inkscape.
2. Even if Inkscape did write out units in length values, paths don't support units. (We have discussed allowing units on paths so maybe this will change in the future.)
In any case, Inkscape should support both ways seamlessly. If it doesn't, it is a bug. In the experimental branch, the default files (A4) now define one 'user-unit' to be 1mm but there also exists an A4 template file with one 'user-unit' equal to 1px so you can choose.
Tav