> The advance-override descriptor scales all character advances of the font face
> by the given percentage. It can be used to match text width between two fonts,
> and hence reduce layout shift caused by web font loading.
> TAG review: > This feature is very similar to ascent-override, descent-override and
> line-gap-override that we shipped earlier. A new TAG review is
> probably not needed.
> Interoperability and Compatibility:
> This is a new feature that CSSWG just resolved to add. We do not expect
> interoperability/compatibility risks if other browsers also implement it.
The CSSWG resolved to add something like this feature, but it did not resolve
on a particular definition of how it behaves. Looking at it for the first time
today, I can say that the spec is both missing details and imho has an
incorrect default for the second parameter.
As for things like TAG review, while the technical implementation of
advance-override is quite similar to ascent-override etc., the impact on text
rendering and readability is *very* different because it changes the
relationship of glyphs within a line, not just the spacing between them. It
needs i18n and a11y review.
As for other details, the current spec -- which is explicitly marked as "not
ready for implementation" by its editors btw -- defines the effect as adding
"tracking", but does not define the ways in which this differs from the
"tracking" added by letter-spacing.