- don't allow partial overwrite of a full-width rune.
- don't allow placement of a full-width rune if it doesn't fit.
- allow callers to also read from the canvas (read-only).
Done here:
- adding helper library which determines area from size and vice versa.
- fixing an off-by-one bug related to area sizes.
- allowing overwrite of cell options by passing an existing cell.Options
instance.
- implementing canvas and its tests.
Jakub Sobon