We need to use Result<> to manage error flow,
at least on the methods API. This way it will
finally feel idiomatic Rust and more concise.
Also, we can't return a non Result from main.
- rename NcResult to NcIntResult.
- new NcError & NcResult types.
- new error![] macro to reduce boilerplate.
- change return type of NcDirect methods to NcResult.
- refactor several examples to return NcResult:
direct-cursor, poc-direct & poc-kittyzapper.
- BONUS: fix test not stopping notcurses context.
- update lib doc-comment.
- fix typo in readme.
- move tests to their own submodules
- move functions reimplementations to reimplemented submodule.
- remove types submodules and move them to their parent.
- add more NcPlane & Notcurses methods
- rename NcChar back to NcEgc, and NcCharBackstop tp NcEgcBackstop
- add ncpile_top & ncpile_bottom functions.
- fix Notcurses stdplane(_mut) methods
- make cell_load_char not return anything since it was always 1.
