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RobinMalfait merged 2 commits into from
May 11, 2026
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Document --default(…) in --value(…) and --modifier(…) #2488

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document `--default(…)`
RobinMalfait May 11, 2026
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highlight certain parts
RobinMalfait May 11, 2026
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39 changes: 39 additions & 0 deletions src/docs/adding-custom-styles.mdx
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Expand Up @@ -580,6 +580,45 @@ The `--value()` function can also take multiple arguments and resolve them left
}
```

#### Default values

Use `--default()` inside `--value()` to support a default value when the utility is used without an explicit value:

```css
/* [!code filename:CSS] */
/* [!code word:--default(4)] */
@utility tab-* {
tab-size: --value(integer, --default(4));
}
```

This matches both `tab-2` and `tab-4`, as well as just `tab` which uses the default value of `4`:

```css
/* [!code filename:Compiled CSS] */
/* [!code highlight:4] */
.tab {
tab-size: 4;
}

.tab-2 {
tab-size: 2;
}
```

The `--default()` function can also be used inside `--modifier()` to provide a default value when no modifier is present:

```css
/* [!code filename:CSS] */
/* [!code word:--default(1)] */
@utility tab-* {
tab-size: --value(integer);
line-height: --modifier(integer, --default(1));
}
```

This matches `tab-2/3` with a line-height of `3`, and `tab-2` with a line-height of `1`.

#### Negative values

To support negative values, register separate positive and negative utilities into separate declarations:
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