zgo.at/termtext

termtext is a Go package to deal with monospace text as interpreted by terminals.

Mostly intended to neatly align/wrap stuff terminal. There are a few tricky bits with this:

• Multiple codepoints can be combined to render one character (or "grapheme cluster" in Unicode speak).
• Some characters are rendered as double-width, such as East-Asian characters, some emojis, and a number of others.
• A single tab can render as multiple spaces, and the number of spaces depends on its position in the string.
• Some characters aren't actually printed to the screen, such as the zero-width space and escape sequences to set the colour.

This package takes care of these issue.

Import as zgo.at/termtext – godoc: https://godocs.io/zgo.at/termtext

The main function is termtext.Width():

Width("\ta")                → 9    Tab expands to 8 spaces, followed by "a".
Width("a\t")                → 8    Tab expands to 7 spaces.
Width("🧑\t🧑")             → 10   🧑 is double-width
Width("\x1b[1mbold\x1b[0m") → 4    Escape sequences are ignored.

You can configure the tab width by setting termtext.TabWidth.

There are a few other functions too:

Expand()            Expand tabs.
Slice()             Slice a string by display width, like str[n:m].

AlignLeft()         Align a string, filling up the remainder with spaces.
AlignRight()
AlignCenter()

Wrap()              Wrap a string. This is a simple wrap which just breaks
                    if a line's width is too long.
WordWrap()          Word-wrap a string: lines are at most w wide, but don't
                    break in the middle of words.