Grapheme count is not a useful number. Even in a monospaced font, you’ll find that the grapheme count doesn’t give you a measurement of width since emoji will usually not be the same width as other characters.

Grapheme count (or rather, indexing) is necessary to do text selection or cursor positions.

Fortunately you can usually outsource this to a UI toolkit which can do it.

For certain use-cases, but it's not like any of the other usual notions of text length are any better for what you want.