PEG ???: New coordinate system definitions

Author: Tuomas J. Lukka
Revision: 1.3
Status: Incomplete

The previous PEGs on coordinate systems were a tad unclear on the overall goals - hopefully these new methods will clarify the picture.

For example, a box coordinate system and an aspect ratio coordinate system (a mapping from (0,w)x(0,1) to (0,1),(0,1)) we can define a padded text coordinate system (i.e. one which has isotropic coordinates relative to the parent coordinate system) based only on these two coordinate systems:

def paddedText(box, aspectratio):