The spec says:
> <delim-token> has a value composed of a single code point.
So using StringView is a bit overkill.
This also allows us to use switch statements in the future.
This doesn't have parsing support for multiple languages in the same
selector. Support for language subcodes is not great either. But it
does do the basics.
In Selectors level 4, `:nth-child()` and `:nth-last-child()` can both
optionally take a selector-list argument. This selector-list acts as a
filter, so that only elements matching the list are counted. For
example, this means that the following are equivalent:
```css
:nth-child(2n+1 of p) {}
p:nth-of-type(2n+1) {}
```
`<forgiving-selector-list>` and `<forgiving-relative-selector-list>` are
the same as regular selector-lists, except that an invalid selector
does not make the whole list invalid. The former is used by the `:is()`
pseudo-class.
For example:
```css
/* This entire selector-list is invalid */
.foo, .bar, !?invalid { }
/* This is valid, but the "!?invalid" selector is removed */
:is(.foo, .bar, !?invalid) { }
```
Also as part of this, I've removed the `parse_a_selector(TokenStream)`
and `parse_a_relative_selector(TokenStream)` methods as they don't add
anything useful.
This resolves the ambiguity between whether a single number is a number
or a ratio. :^)
Also removed the "no more tokens" checks from
deea129b8c - that logic was completely
wrong, since there are always tokens after a value in the `(123 < foo <
456)` syntax.
As noted, the Parser can't handle the `<number>` syntax for this - it
gets parsed instead by the `<number>` branch. We can't actually resolve
the ambiguity without making the Parser aware of what type each
media-feature is, but I will get to that soon. :^)
For now, we only understand `none`, `normal`, `<image>` and `<string>`.
The various other functions and identifiers can be added later.
We can *almost* use a StyleValueList for this, except it's divided into
two parts - the content, and the optional "alt text". So, I've added a
new StyleValue for it.
This is the only dimension type besides `<length>` that is used in any
media queries in levels 4 or 5 right now. Others can be included
if/when they're needed.
This means the units are defined in a single place instead of two.
Also removed the verify that we didn't produce a bogus % dimension token
in the Tokenizer, since this has never happened and the parser is not a
tokenizer test suite. :^)
When converting this code to use Optional, I accidentally left in the
initialization, so it *always* had a value, and always created a Length
from it. Oops.
The pattern we've adopted for other multi-value properties is to run in
a loop like this, since that makes it easier to cater for values
appearing in different orders.
During the LengthPercentage split, I converted the individual-corner
`border-foo-bar-radius` properties to LengthPercentage but forgot
`border-radius` itself! Oops. Discord's CSS was doing `border-radius:
50%` a lot, so this cuts down on CSS parser spam.
Browser has a handy debug menu option to dump all stylesheets, so we
don't need to spam the console with this. (All the spam massively slows
down page loads.)
See https://www.w3.org/TR/css-values-3/#calc-type-checking
If the sub-expressions' types are incompatible, we discard the calc() as
invalid.
Had to do some minor rearranging/renaming of the Calc structs to make
the `resolve_foo_type()` templates work too.
This lets us produce valid CSS in its to_string() method, instead of
always adding commas as before. :^)
Also, finally added a Formatter for StyleValues.
This is in a slightly weird state, where Percentages are sometimes
Lengths and sometimes not, which I will be cleaning up in subsequent
commits, in an attempt not to change all of LibWeb in one go. :^)
This means you can now do queries like:
```css
@media (400px <= width < 800px) { }
```
Chromium and Firefox which I tested with both don't support this yet, so
that's cool. :^)
Past me decided that the grammar was overly verbose and I could do it
better myself. Which seemed fine until the spec changed and I didn't
know how to integrate the changes. Lesson learned! :^)
Rather than have a function for every single part of the grammar, I have
written some as lambdas, and combned `<media-condition>` and
`<media-condition-without-or>` into one function. But otherwise it's
close to the spec, with comments listing the part of the grammar being
parsed, so hopefully it will be easier to make future adjustments!
This does not add any new functionality.
Web::CSS::MediaQuery::MediaFeature::Type was getting a bit ridiculous!
Also, this moves the detection of "min-" and "max-" media-features into
the MediaFeature itself, since this is an implementation detail, not
part of the spec.
Previously, we were using StyleValues for this, which was a bit of a
hack and was brittle, breaking when I modified how custom properties
were parsed. This is better and also lets us limit the kinds of value
that can be used here, to match the spec.
If a property is custom or contains a `var()` reference, it cannot be
parsed into a proper StyleValue immediately, so we store it as an
UnresolvedStyleValue until the property is compute. Then, at compute
time, we resolve them by expanding out any `var()` references, and
parsing the result.
The implementation here is very naive, and involves copying the
UnresolvedStyleValue's tree of StyleComponentValueRules while copying
the contents of any `var()`s it finds along the way. This is quite an
expensive operation to do every time that the style is computed.
Now that we can serialize CSS tokens, we can just hold a string and then
re-parse it when the Supports is evaluated. This feels a little weird,
but it only happens once so it's not going to slow it down much, and it
keep the API cleaner.
The changes in commit d462a6720a meant
that `CSSLoader::load_next_import_if_needed()` was no longer being
called, so no `@import` rules were loading.
The spec does not seem to mention when that loading should take place,
but WebKit does this at parse time, as each rule is added to the style
sheet. If it works for them, it's probably not that bad. :^)
So, that's what we now do here. The `CSSImportRule` creates a fetch
request when it is constructed, so each one is responsible for its own
contents.
Like the `background-foo` longhand properties (except
`background-color`), `background` allows multiple layers to be defined,
separated by commas. A layer does not necessarily contain something to
actually draw!
This parses as a `BackgroundStyleValue`, holding a `StyleValueList` for
each property. This is mostly to make expansion into longhands simpler -
if we had a list of `BackgroundStyleValue`s instead, one per layer, then
we would have to break it up per-property anyway when computing styles.
We now can parse lists of values for these properties:
- `background-attachment`
- `background-clip`
- `background-image`
- `background-origin`
- `background-position`
- `background-repeat`
- `background-size`
This uses two new Parser methods:
`parse_simple_comma_separated_value_list()` for the simple case when
each value is parsed from a single token; and
`parse_comma_separated_value_list()` which takes a lambda for when
parsing each value is more involved.
This also means that any unconsumed tokens at the end will make the
parsing fail as it should, where previously we just ignored them.
...as opposed to storing StyleValues, which we have to later check are
IdentifierStyleValues, which store identifiers that we can convert to
Repeat values later. It's fewer allocations, and we can't end up with
invalid values by mistake. :^)
This is step 1 in removing the two `background-repeat-x/y`
pseudo-properties. Since adding the concept of compound StyleValues, we
don't need `background-repeat` to be split in two any more.
This is done a bit differently from other properties: using a
TokenStream instead of just a Vector of ComponentValues. The reason for
this is, we can then use call the same function when parsing the
`background` shorthand. Otherwise, we would have to know in advance how
many values to pass down, which basically would involve duplicating the
`background-position` parsing code inside `background`.
The StyleValue is PositionStyleValue, since it represents a
`<position>`: https://www.w3.org/TR/css-values-4/#typedef-position
Unfortunately, background-position's parsing is a bit different from
`<position>`'s, (background-position allows 3-value syntax and
`<position>` doesn't) so we'll need to come back and write a different
parsing function for that later.
This accounts for cases like:
```css
.foo {
color: blue ! important ;
}
```
That's rare now that minifying is so popular, but does appear on some
websites.
I've added spec comments to `consume_a_declaration()` while I was at it.
Noticed this while checking some MediaWiki-based sites. It's not
obvious, but the spec does allow this, by not mentioning it in this list
of places whitespace is forbidden:
https://www.w3.org/TR/selectors-4/#white-space
The only reason it wasn't const before (and why we had a const_cast
hack) was to support ImageStyleValue's constructor taking it, which no
longer applies. `hack_count--;` :^)
This always felt awkward to me, and required a few other hacks to make
it work. Now, the request is only started when `load_bitmap()` is
called, which we do inside `NodeWithStyle::apply_style()`.
Previously, `box-shadow: none` would fail to parse, meaning that in this
example:
```css
p {
box-shadow: 20px 10px 5px magenta;
}
p.foo {
box-shadow: none;
}
```
... a `<p class="foo">` would still have a box-shadow, when it should
not have one. Now, we handle the `none` value. :^)
We can reduce the amount of padding the compiler adds in order to
ensure data alignment of member variables by ordering the types in
a struct by size in decending order.
Found By PVS-Studio: https://pvs-studio.com/en/docs/warnings/v802/
The main thing missing is that we don't serialize the supports clause,
but for actually using a `@supports (something: cool) {}` rule in CSS,
it works!
