Support the extended `supports <font-technology>` syntax of the @font-face src: descriptor. The intention of this syntax is to enable UA's to choose supported entries from the src: line of the @font-face. Unsupported entries with "support..." lines which are not supported are to be dropped from the src: line.
Supporting this syntax enables an inexpensive CSS or JS based check for support of CORLv1 or other font technologies. CSS based selection of the right font and technology is done by the UA traversing the src: line and choosing the first successfully parsed and supported entry and trying to load it. If the load fails, the next supported entry is choosen. JS feature testing can be achieved by declaring a CSS @font-face in a stylesheet with a src: line that contains for example a line src: format(woff2) supports COLRv1; - then accessing this rule using CSSOM and retrieving the value of cssText for this rule. By analysing the values of cssText, specifically the serialized src: line, it can be determined whether entries were dropped from the src: line. Support for this feature across browsers allows precise selection of the best, supported font technology from the @font-face definition.
Specification being incubated in a Community Group
Status in Chromium
Consensus & Standardization
Search tagscss, @font-face, src, descriptor, src descriptor,
Last updated on 2021-10-05