- Want to first draw lines before doing anything that requires measuring

- Need to know scroll position to know what to draw

- Or, in some other way, estimate which parts to draw

  - From cursor: if it looks like cursor will be outside, find side to
    align cursor with, plus screenheight above/below it

  - From absolute number -- don't need to measure before redraw

  - Offset is like abs number

- So instead of pixel viewport, allow either pixels or lines.

  - Or always convert to lines?