bug#48734: 28.0.50; Performance regression in `string-width`?

[Lars Ingebrigtsen]

Eli Zaretskii <eliz@gnu.org> writes:

> If deft-mode wants to allocate space on display, then they really do
> need to use string-width, but then the changes which make them "hang"
> are really important, because before that string-width would compute
> the result incorrectly when characters are composed on display.

string-width has always been approximate (but fast), hasn't it?  And to
determine the actual display width you've had to use
window-text-pixel-size or the like.

Perhaps string-width should get an extra parameter to get the new, more
accurate computation, and get the old, fast computation without this
parameter.

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