- Use lenses in core library
- Use With/SetSize to track list element sizes for variable element prim
  heights
- Fix cursor cropping in render function where missing
- Deal with multi-column characters everywhere
- Implement 2-d text editing
- Write benchmarks for render on various primitive types
- Use Vector instead of List where sensible
- Implement region-to-view scrolling instead of point-to-view
- Think about porting some widgets from vty-ui
- Think of better library name
- Support "suggested" vs "forced" attributes in Prim rendering
- List: add listGetSelected :: List a -> Maybe (Int, a)
- Make width and height values newtypes
- Do we need CropLeftBy and CropTopBy if we just Translate negatively?