widecharwidth

>For example, iTerm2 considers the "rosette" emoji to have width 1 It's not the case here, but for some emoji there's another issue: Unicode 9 changed the width for some codepoints (mostly emoji) from 1 to 2, and iTerm until very recently (don't know if it's released yet) defaulted to the Unicode 8 widths, with an opt-in escape sequence to change to Unicode 9. >This approach comes from the wcwidth utility, and the comment at the top of the C source file provides further insight into the difficulties faced here. That's link goes to Markus Kuhn's implementation from 2007. It supports Unicode 5, and is by now woefully out of date. You don't want to use it anymore. Most terminals have their own definition, and the annoying part is that the client application and the terminal need to have theirs in sync or they get weird glitches when moving

If you're measuring text for terminal display, you might like my "widecharwidth" library. It tries to be what wcwidth should have been. http://github.com/ridiculousfish/widecharwidth

With fish we've made the experience that relying on libc isn't good enough. Specifically in the case of connecting to a server that typically has an old libc with old unicode information, from a desktop that has a much newer system, or in case of ambiguous characters, where libc will just give you one width that might not match what the terminal actually renders (and they frequently have configuration options to change it!). So we've made something we call widecharwidth (https://github.com/ridiculousfish/widecharwidth), which is a python script that parses the unicode datafiles (UnicodeData.txt, emoji-data.txt and friends) and generates a header you can #include. And someone's opened a PR to mosh to integrate it: https://github.com/mobile-shell/mosh/pull/1143