Set font size in cap height

The current ways of specifying font size are quite problematic in UI assuming an exact text height: different fonts can have different height at one pixel size. Would be very nice if Qt had API to specify cap height instead and Qt would automatically find the right font sizes for all the fonts (including fallback fonts) used by the text rendered with such QFont set.

Here's an interesting article which looks related to the problem: https://tonsky.me/blog/font-size/. The line height part is interesting as well as different fonts seem to be rendered having the center higher or lower which is apparently related to that and would be nice to get rid of, too.