For pseudo elements that represent a browser-generated shadow tree
element, such as ::placeholder, we were reparsing their style attribute
in StyleComputer for some reason.
Instead of doing this, just access the already-parsed version via
Element::inline_style().
These are created when a style rule has properties listed after another
rule. For example:
```css
.test {
--a: 1;
--b: 1;
--c: 1;
.thing {
/* ... */
}
/* These are after a rule (.thing) so they're wrapped in a
CSSNestedDeclarations: */
--d: 1;
--e: 1;
--f: 1;
}
```
They're treated like a nested style rule with the exact same selectors
as their containing style rule.
For example, this:
```css
.foo {
color: red;
&:hover {
color: green;
}
}
```
now has the same effect as this:
```css
.foo {
color: red;
}
.foo:hover {
color: green;
}
```
CSSStyleRule now has "absolutized selectors", which are its selectors
with any `&`s resolved. We use these instead of the "real" selectors
when matching them, meaning the style computer doesn't have to know or
care about where the selector appears in the CSS document.
Through the CSSOM, rules can be moved around, and so anything cached
(for now just the qualified layer name) needs to be recalculated when
that happens. This method is virtual so that other rules will be able
to clear their cached data too.
A couple of parts of this:
- Store the source text for Declarations of custom properties.
- Then save that in the UnresolvedStyleValue.
- Serialize UnresolvedStyleValue using the saved source when available -
that is, for custom properties but not for regular properties that
include var() or attr().
This is in a weird position where the spec tells us to discard the
comments, but then we have to preserve the original source text which
may include comments. As a compromise, I'm treating each comment as a
whitespace token - comments are functionally equivalent to whitespace
so this should not have any behaviour changes beyond preserving the
original text.
Previously we would serialize these as the empty string. eg, this:
```
<div style="grid-auto-columns: auto"></div>
```
would have a computed `grid-auto-columns` value of ``.
In order to know whether `calc(2.5)` is a number or an integer, we have
to see what the property will accept. So, add that knowledge to
`Parser::expand_unresolved_values()`.
This makes `counter-increment: foo calc(2 * var(--n));` work correctly,
in a test I'm working on.
This will be the first step is making better use of system libraries
like fontconfig and CoreText to load system fonts for use by the UI
process and the CSS style computer.
These don't have to worry about the input not being valid UTF-8 and
so can be infallible (and can even return self if no changes needed.)
We use this instead of Infra::to_ascii_{upper,lower}_case in LibWeb.
CSS Syntax 3 (https://drafts.csswg.org/css-syntax) has changed
significantly since we implemented it a couple of years ago. Just about
every parsing algorithm has been rewritten in terms of the new token
stream concept, and to support nested styles. As all of those
algorithms call into each other, this is an unfortunately chonky diff.
As part of this, the transitory types (Declaration, Function, AtRule...)
have been rewritten. That's both because we have new requirements of
what they should be and contain, and also because the spec asks us to
create and then gradually modify them in place, which is easier if they
are plain structs.
There was no need to use FlyString for error messages, and it just
caused a bunch of churn since these strings typically only existed
during the lifetime of the error.
When the TokenStream code was originally written, there was no such
concept in the CSS Syntax spec. But since then, it's been officially
added, (https://drafts.csswg.org/css-syntax/#css-token-stream) and the
parsing algorithms are described in terms of it. This patch brings our
implementation in line with the spec. A few deprecated TokenStream
methods are left around until their users are also updated to match the
newer spec.
There are a few differences:
- They name things differently. The main confusing one is we had
`next_token()` which consumed a token and returned it, but the spec
has a `next_token()` which peeks the next token. The spec names are
honestly better than what I'd come up with. (`discard_a_token()` is a
nice addition too!)
- We used to store the index of the token that was just consumed, and
they instead store the index of the token that will be consumed next.
This is a perfect breeding ground for off-by-one errors, so I've
finally added a test suite for TokenStream itself.
- We use a transaction system for rewinding, and the spec uses a stack
of "marks", which can be manually rewound to. These should be able to
coexist as long as we stick with marks in the parser spec algorithms,
and stick with transactions elsewhere.
Before this change, we transferred the input element's line-height to
both the editable text *and* the placeholder. This caused some strange
doubling of the effective line-height when the editable text was empty,
pushing down the placeholder.
Transitions are currently not implemented for pseudo elements which
causes the transition to be applied to the "real"/"parent" element. When
a transition adjusts width/height on a pseudo element this causes the
real elements layout to break.
As a quick fix we just skip doing transitions when they are against
pseudo elements.
Before this change we were serializing them in a bogus 8-digit hex color
format that isn't actually recognized by HTML.
This code will need more work when we start supporting color spaces
other than sRGB.
