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[css-sizing] Production for values common to max/min/preferred widths and heights #13478
Description
Could css-sizing-3 please introduce something like <box-length> or <box-dimension> = <length-percentage [0,∞]> | min-content | max-content | fit-content(<length-percentage [0,∞]>) | <calc-size()>?
With that production, <'width'>, <'height'>, <'min-width'>, <'min-height'> could be simplified to auto | <box-dimension>, whereas <'max-width'>, <'max-height'> could become none | <box-dimension>. This would make the difference more noticeable.
css-sizing-4 can then add stretch | fit-content | contain to it.
css-logical refers to <'width'> and <'min-width'> and <'max-width'>. Although this is the future-safe way, it feels a bit weird that the height properties also use a width value.
css-flexbox could either keep its content | <'width'> value syntax for the flex-basis property, or switch to auto | content | <box-dimension>.
There may be other places affected.
Activity
[css-sizing-3][css-sizing-4] Introduce <box-size> production to conso…
fantasai commentedon Sep 3, 2026
Done! Thanks for the suggestion, @Crissov, this is much better. We named it
<box-size>. Leaving the issue open to track edits for css-flexbox and css-multicol.Crissov commentedon Sep 3, 2026
Fair – I think I did not suggest
<box-size>because I believe the newsizeproperty shouldbehave been calledbox-sizeand it would then be confusing to also have<'box-size'>.fantasai commentedon Sep 3, 2026
Oh, that got named to
sizealready, see #820.cdoublev commentedon Sep 4, 2026
The ec88f45 rewrite appears to have many problems. Below are the property value definitions (ignoring those from CSS Logical) before/after, with expanded
<box-size>and concatenatedNew values.block-size,inline-size,min-block-size,min-inline-sizeheight,width,min-height,min-widthcolumn-widthmax-block-size,max-inline-sizemax-height,max-wifthNote that
calc-size()in the RHS of a production represents a function taking no argument.cdoublev commentedon Sep 30, 2026
Re-opening because a few problems remain (1-4).
The logical sizing properties were imported from CSS Logical 1 to CSS Sizing 3 by f2234ba, (1) but the initial value of
min-block-sizeandmax-block-sizemin-inline-sizechanged from0toautoalong the way.Originally,
column-widthwas defined in CSS Multi-Column Layout withauto | <length [0,∞]>, and CSS Sizing extended it with some sizing keywords.Then ec88f45 extended it with
<box-size>, which produces these sizing keywords and other values like<length-percentage [0,∞]>(2) but how to interpret<percentage>forcolumn-widthis not defined. (3) I suspect thatcontainand<calc-size()>may also not be expected as new values forcolumn-width.Since
<length-percentage [0,∞]>overlapped with<length [0,∞]>, 20e4b18 was intended to replace theseNew valueswith a completeValuedefinition:auto | <box-size>. However, (4) it did not imported the other property table definition fields from CSS Logical. This forcesw3c/webrefusers to manually merge definitions from the two specifications.For (4), I was going to propose these changes until I ran into (2):
Perhaps the best solution would be to revert using
<box-size>to definecolumn-width?cc @tidoust
fantasai commentedon Oct 8, 2026
This is correct. The initial value is supposed to match between properties that map to each other. (CSS Logical was written before we changed the initial value, so it matched when it was written.)
fantasai commentedon Oct 8, 2026
Opened #14574 for the
column-widthissue.@cdoublev Is there anything else that needs addressing here?
cdoublev commentedon Oct 8, 2026
Nope, thank you.
Loirooriol commentedon Oct 8, 2026
Presumably that's a typo for
min-inline-size, because max sizing properties don't even acceptauto. So if something says it's the initial value, it's wrong.