This is a fairly far-reaching commit. The idea is:
* Introduce a unicode_version config that specifies the default level
of unicode conformance for each newly created Terminal (each Pane)
* The unicode_version is passed down to the `grapheme_column_width`
function which interprets the width based on the version
* `Cell` records the width so that later calculations don't need to
know the unicode version
In a subsequent diff, I will introduce an escape sequence that allows
setting/pushing/popping the unicode version so that it can be overridden
via eg: a shell alias prior to launching an application that uses a
different version of unicode from the default.
This approach allows output from multiple applications with differing
understanding of unicode to coexist on the same screen a little more
sanely.
Note that the default `unicode_version` is set to 9, which means that
emoji presentation selectors are now by-default ignored. This was
selected to better match the level of support in widely deployed
applications.
I expect to raise that default version in the future.
Also worth noting: there are a number of callers of
`unicode_column_width` in things like overlays and lua helper functions
that pass `None` for the unicode version: these will assume the latest
known-to-wezterm/termwiz version of unicode to be desired. If those
overlays do things with emoji presentation selectors, then there may be
some alignment artifacts. That can be tackled in a follow up commit.
refs: #1231
refs: #997
@chipsenkbeil: I spotted a latent bug in here that got fixed as
a side effect of this change. For `write_file` and possibly others,
reply.try_send was only called in the case where file_id was valid.
For an invalid id, I think the caller could hang.
Not sure if this was a problem in practice, but I wonder if it might
have contributed to some of the weird state issues you mentioned.
This works, but on macOS, there is a segfault in openssl when the
session is closed... I'm going to try this on Linux to see if it
is consistent behavior and ponder next steps.
The port number is guaranteed to be set in the config parser,
just like for the host and user, so the unwrap is "OK", but it's
less brittle to handle the error consistent with the others here.
