[css-fonts-4] [varfont] Consider not clamping single values in @font-face descriptors

[litherum]

Currently, @font-face blocks are used like:

@font-face {
    font-family: "MyCoolFont";
    font-weight: 700;
    src: url("MyCoolFont.ttf") format("truetype");
}

<div style="font-family: 'MyCoolFont'; font-weight: 800;">

Let's pretend this web author then replaces their font file with a variable font which support weight ranges 600 - 900. In this situation, the page wouldn't look different, because the font-weight descriptor will clamp the request to the range [700, 700], so the value applied would be 700, which is the same as what the original file would have rendered.

However, the request was for weight 800, and the font supports weight 800. Perhaps we should consider font-weight: 700 distinctly from font-weight: 700 700 in the @font-face block. This would mean that web authors would have to opt-in to the clamping behavior by setting an explicit range.

[svgeesus]

IIRC the original intention was that descriptors supported ranges. It certainly makes sense for descriptors on variable fonts to describe the range of values available on any axis. So in this example, the descriptor should say 600 to 900 and thus, 800 should match.

[litherum]

Do you mean that, whenever someone updates a font file to point to a variable font, they should also update any @font-face rules which refer to it?

[litherum]

I suppose they should be updating the @font-face block anyway to update the format() function (or whatever we come up with in #633)

[svgeesus]

Do you mean that, whenever someone updates a font file to point to a variable font, they should also update any @font-face rules which refer to it?

Yes, exactly.