The coordinate systems in PP
A sketch of the overall PP view
The Focus+Context zooming in left panel.
There are several coordinate systems...
Each viewport consists of two main coordinate systems: the frame to root coordinate system and the paper to screen coordinate system, which is constructed from the paper to viewport coordinate system.
The box of the frame coordinate system decides the location of the frame.
The system of coordinate systems inside a single irregularframe of the final view. There is one of each coordsys, except for contentToScreen.
