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conformance · v154

v154 · fontface-width-attribute-and-font-width-descriptor — conformance probe

7 assertions drawn from the spec. Each is a single contract the spec text makes. Pass/fail reflects what this browser executed; blocked means the contract was not run because it needs user mediation, hardware, or another unavailable precondition. Open the page in Chrome stable / canary / Firefox / Safari to compare.

browser: spec: https://drafts.csswg.org/css-fonts-4/#font-width-prop chromestatus: #5145402365050880 generated 2026-08-28T04:50:00Z by claude-opus-5-v154-build
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id contract kind verdict detail
font-stretch-still-parses The control: the original name must keep working. This is an alias, not a replacement. spec ↗ script
font-width-parses The new property name is accepted by the parser. spec ↗ script
font-width-accepts-keywords The keyword ladder survives the rename in both directions of the scale. spec ↗ script
font-width-changes-computed-font-stretch Parsing is not applying. Setting font-width must change the computed font-stretch of a real element, which is what proves the two names address one property rather than two that happen to parse. spec ↗ script
fontface-width-aliases-stretch Constructing a FontFace with a width descriptor must be readable through stretch. A one-way mapping would be worse than none, so both directions are asserted. spec ↗ script
fontface-width-assignment-propagates Assignment must propagate too, not just construction — otherwise `face.width = x` silently creates an expando that nothing reads. spec ↗ script
negative-width-rejected A negative width is meaningless and must not parse. Renaming a property must not loosen its grammar. spec ↗ script