Render emoji as double width

As of Unicode 9.0, emoji should be treated as East Asian Wide (see http://www.unicode.org/versions/Unicode9.0.0/). From https://github.com/gnachman/iTerm2/blob/6d5e51aa7a797e0a510c1aee5b53b13b02d3d049/sources/NSCharacterSet%2BiTerm.m, it appears that iTerm2 implements its own wcwidth equivalent. Could this be updated for Unicode 9.0? I would submit a PR myself, but I'm not sure if this file was generated automatically somehow from one of the Unicode data files. Here is an example of a similar change to the wcwidth Python library.

I gather this is for homebrew or Linux or some such, since the default wcwidth on macOS will surely be mired in the past for a long time.

I haven't switched over because I'm afraid it'll break more than it fixes, so it needs to be a setting (at least!) and probably an escape sequence as well.

PR 294 is a start on this.

Milestone changed to %Next Beta

My personal use-case is an emoji in my prompt for xonsh, which uses the aforementioned wcwidth Python library, which now things emoji are wide, causing iTerm2 to print an extra space after it from what is intended.

I didn't think to check for PRs yet, sorry about that.

You can now select unicode 9 character widths in the text profiles prefs pane. More docs on unicode version switching here: https://gitlab.com/gnachman/iterm2/wikis/unicodeversionswitching

Status changed to closed