Dependency Cycles via Relative Units with unit algebra
Loirooriol opened this issue · 3 comments
#315 was fixed without considering "unit algebra". CSS Values 4 allows dividing by dimensions, so we may have
@property --my-font-size {
syntax: "<number>";
inherits: false;
initial-value: 0;
}
div {
--my-font-size: calc(10em / 1px);
font-size: calc(var(--my-font-size) * 1px);
}
That's a dependency cycle! It's not addressed by https://drafts.css-houdini.org/css-properties-values-api/#dependency-cycles, since that only handles registered properties with a syntax of <length>
or <length-percentage>
.
The example above uses <number>
, but other dimensions like <angle>
are also affected:
--my-font-size: calc(10em / 1px * 1deg);
font-size: calc(var(--my-font-size) / 1deg * 1px);
CC @tabatkins
Hm, indeed. I think the solution is just to remove the "length or length-percentage" condition (replace it with a "not *" condition, probably), so we add those edges any time the relevant values are used.
Actually we need more than that, because https://drafts.css-houdini.org/css-properties-values-api/#dependency-cycles isn't really addressing the problem with lengths:
@property --foo {
syntax: "<length>";
inherits: false;
initial-value: 0px;
}
div {
--foo: 10ex;
font-weight: calc(var(--foo) / 1px);
}
The ex
unit depends on font-weight
, but the directed dependency graph is not aware of it, since there is only an edge to font-size
, not font-weight
.
Following w3c/csswg-drafts#8169 (comment), I guess we should add an edge to every "font-* property (and anything else that affects font selection)".