This implements the `is_valid_in_the_current_context()` methods by
maintaining a stack of contexts, such as whether we're inside a style
rule, or an `@media` block, or the condition of a `@supports` rule.
This class was being copied all over the place, however, most of these
cases can be easily prevented with `auto const&` or `NonnullRawPtr<>`.
It also didn't have a move constructor, causing `Vector` to copy on
every resize as well.
Removing all these copies results in an almost 15% increase in
performance for CSS parsing, as measured with callgrind.
This updates the CSS parser to support the keyword 'none' in the CSS4
color functions. The underlying CSSColorValue already supports this
keyword, meaning the parser can instantiate the color directly.
This is an attempt to bring the size of Parser.cpp down. No code
changes, just moves and some explicit template instantiations now that
we're using them from a different file.
Better support for CSS shorthands when setting the style attribute. This
improves some tests in WPT /css/css-align/default-alignment/*shorthand.
When setting the style attribute in JS via element.style = '..' or the
setAttribute method, shorthand properties were not expanded to longhand
properties.
This is really bare bone as we only support the `xyz-d50` color space
for the moment.
It makes us pass the following WPT tests:
- css/css-color/predefined-016.html
- css/css-color/xyz-d50-001.html
- css/css-color/xyz-d50-002.html
The support in LibWeb is quite easy as the previous commits introduced
helpers to support lab-like colors.
Now for the methods in Color:
- The formulas in `from_lab()` are derived from the CIEXYZ to CIELAB
formulas the "Colorimetry" paper published by the CIE.
- The conversion in `from_xyz50()` can be decomposed in multiple steps
XYZ D50 -> XYZ D65 -> Linear sRGB -> sRGB. The two first conversion
are done with a singular matrix operation. This matrix was generated
with a Python script [1].
This commit makes us pass all the `css/css-color/lab-00*.html` WPT
tests (0 to 7 at the time of writing).
[1] Python script used to generate the XYZ D50 -> Linear sRGB
conversion:
```python
import numpy as np
# http://www.brucelindbloom.com/index.html?Eqn_ChromAdapt.html
# First let's convert from D50 to D65 using the Bradford method.
m_a = np.array([
[0.8951000, 0.2664000, -0.1614000],
[-0.7502000, 1.7135000, 0.0367000],
[0.0389000, -0.0685000, 1.0296000]
])
# D50
chromaticities_source = np.array([0.96422, 1, 0.82521])
# D65
chromaticities_destination = np.array([0.9505, 1, 1.0890])
cone_response_source = m_a @ chromaticities_source
cone_response_destination = m_a @ chromaticities_destination
cone_response_ratio = cone_response_destination / cone_response_source
m = np.linalg.inv(m_a) @ np.diagflat(cone_response_ratio) @ m_a
D50_to_D65 = m
# https://en.wikipedia.org/wiki/SRGB#From_CIE_XYZ_to_sRGB
# Then, the matrix to convert to linear sRGB.
xyz_65_to_srgb = np.array([
[3.2406, - 1.5372, - 0.4986],
[-0.9689, + 1.8758, 0.0415],
[0.0557, - 0.2040, 1.0570]
])
# Finally, let's retrieve the final transformation.
xyz_50_to_srgb = xyz_65_to_srgb @ D50_to_D65
print(xyz_50_to_srgb)
```
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.
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().
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.
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.
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 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.
Multiple font properties are either the `normal` keyword or some
non-keyword value, so this lets us avoid some boilerplate for those, at
the cost of the existing `none` users having marginally more verbose
code.
This is a special form of `<string>` so doesn't need its own style value
type. It's used in a couple of font-related properties. For completeness
it's included in ValueType.
