This PR replaces the default spacing scale (`--spacing-*`) with a
generative system based on a default spacing _unit_.
Instead of the default theme containing values like `--spacing-4`,
`--spacing-6`, `--spacing-8`, etc., instead we just define a single
`--spacing` value:
```css
@theme {
--spacing: 0.25rem;
}
```
Utilities like `px-4` are derived from this unit by multiplying it by
the value in the utility (4 in this case):
```css
.px-4 {
padding-inline: calc(var(--spacing) * 4);
}
```
The biggest consequence of this change is that every value is available
now, rather than just the explicitly configured values.
This means utilities like `px-42` will work now, whereas prior to this
PR only `px-40` and `px-44` were valid utilities. I personally found it
very difficult to know which values actually existed at the higher end
of the scale without IntelliSense, and in practice even when working
with a skilled designer like [Steve](https://x.com/steveschoger) who
helped design Tailwind's default spacing scale, I'd very often need to
break out of it to implement a design, and trying to round to a value
that was in the scale made the design worse, not better.
This PR allows you to use any whole number, as well as decimal numbers
that are multiples of `0.25` to ensure classes like `px-1.5` continue to
work. While this means you can now technically do things like
`pt-97.25`, I think the presence of the fractional value will be enough
of a signal to developers that they are doing something a little
unusual, and they can use their judgment as to whether they are making
the right decision or not.
I'll update this PR with a lot more detail when I have a chance, as
there are a few other things to explain like:
- Unifying all of the values for
width/min-width/max-width/height/min-height/max-height utilities
- Deriving numeric line-height values from the spacing multiplier
instead of a separate line-height scale
- Using `--spacing: initial` to disable the multiplier
- How you can still use an explicit spacing scale and ignore this change
- How we plan to use IntelliSense to surface a more curated set of
spacing values even if smaller increments work when you type them
explicitly
---------
Co-authored-by: Adam Wathan <4323180+adamwathan@users.noreply.github.com>
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