[css-fonts] Font matching algorithm; issue with weight selection #1701
Description
This issue is related to the font-weight section of the font-matching algorithm (https://github.com/w3c/csswg-drafts/blob/master/css-fonts/Fonts.html#L3383).
When an exact match is not available for the specified weight, I believe the browser should instead choose the nearest available weight (with rules for tie-breaks obviously). This is very useful when you need to have multiple fallback fonts for different platforms, and one font has weights 400,500,700 (say), and another 400,600,700. For semi-bold text I want 500 from the first font, or 600 if the second font. The logical way to do this is to specify font-weight: 550, however with the current algorithm this would map to 700 rather than 500 in the first font. There is no way to specify this choice with the current algorithm.