Now that StyleResolver is going to deal with StyleComponentValueRules,
it will need to be able to parse those into StyleValues, using
`parse_css_value()`.
Also added StyleValue::is_builtin_or_dynamic(), which returns true for
values that are valid anywhere - things like `initial` and `inherit`,
along with `var()`, `attr()` and `calc()` - which we want to test for
easily.
As the new CSS parser tokenizes its input, we can no longer easily
rely on a StringStyleValue for multi-value properties. (eg, border)
ValueListStyleValue lets us wrap all of the ComponentValues that
the Parser produced for one declaration, as a single StyleValue, to
then be parsed into StyleValues by the StyleResolver.
Originally, I wanted it to be a list of StyleValues, but several
properties use syntax that makes use of non-StyleValue tokens, eg:
```css
/* Syntax using a / */
font: 12px/14px sans-serif;
/* Multiple values separated by commas */
background: url(catdog.png), url(another-image.jpg), blue;
```
Passing the ComponentValue tokens themselves means that all that
information is carried over. The alternative might be to create a
StyleValue subclass for each property and parse them fully inside
the Parser. (eg, `FontStyleValue`)
I decided against `ListStyleValue` as a name, to avoid confusion
with list styles. It's not ideal, but names are hard.
This doesn't exactly do what you would think from its name: It surely
adds an extra leading zero to the front of a number, but only if the
number is less than 10. CSS is weird sometimes.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
The background-repeat value may be specified as either one- or two-value
identifiers (to be interpreted as horizontal and vertical repeat). This
adds two pseudo-properties, background-repeat-x and background-repeat-y,
to handle this. One-value identifiers are mapped to two-value in
accordance with the spec.
