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LibWeb: Store font-weight in ComputedProperties in computed form

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We now also more closely follow the spec when computing values for
font-weight and we now:
 - Support relative lengths in `calc()`s
 - Properly clamp `calc()`s
 - Support relative keywords (e.g. lighter, bolder)
 - Respect that font-weight can be a non-integer number.

This does expose a few false positives in the font-weight-computed.html
WPT test. This is because we don't recompute non-inherited font-weight
within `recompute_inherited_style` which means that relative keyword
values can fall out of sync with their parent's value. These previously
passed as we treated `bolder` and `lighter` as aliases for `bold` and
`normal` respectively.
This commit is contained in:
Callum Law 2025-09-02 01:14:06 +12:00 • committed by Sam Atkins
commit 39484e2027
Notes: github-actions[bot] 2025-09-19 09:08:40 +00:00
15 changed files with 214 additions and 117 deletions
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105
Libraries/LibWeb/CSS/StyleComputer.cpp
View file

@ -1043,8 +1043,6 @@ void StyleComputer::collect_animation_into(DOM::AbstractElement abstract_element
});
}
DOM::AbstractElement abstract_element { element, pseudo_element };
auto const& inheritance_parent = abstract_element.element_to_inherit_style_from();
auto inheritance_parent_has_computed_properties = inheritance_parent.has_value() && inheritance_parent->computed_properties();
auto parent_length_resolution_context = inheritance_parent_has_computed_properties ? Length::ResolutionContext::for_element(inheritance_parent.value()) : Length::ResolutionContext::for_window(*m_document->window());
@ -1065,6 +1063,17 @@ void StyleComputer::collect_animation_into(DOM::AbstractElement abstract_element
result.set(PropertyID::FontSize, font_size_in_computed_form);
}
if (auto const& font_weight_specified_value = specified_values.get(PropertyID::FontWeight); font_weight_specified_value.has_value()) {
auto inherited_font_weight = inheritance_parent_has_computed_properties ? inheritance_parent->computed_properties()->font_weight() : InitialValues::font_weight();
auto const& font_weight_in_computed_form = compute_font_weight(
*font_weight_specified_value.value(),
inherited_font_weight,
parent_length_resolution_context);
result.set(PropertyID::FontWeight, font_weight_in_computed_form);
}
PropertyValueComputationContext property_value_computation_context {
.length_resolution_context = {
.viewport_rect = viewport_rect(),
@ -1086,7 +1095,7 @@ void StyleComputer::collect_animation_into(DOM::AbstractElement abstract_element
if (!style_value)
continue;
if (first_is_one_of(property_id, PropertyID::FontSize))
if (first_is_one_of(property_id, PropertyID::FontSize, PropertyID::FontWeight))
continue;
auto const& computed_value = compute_value_of_property(property_id, *style_value, get_property_specified_value, property_value_computation_context);
@ -1836,10 +1845,12 @@ CSSPixels StyleComputer::relative_size_mapping(RelativeSize relative_size, CSSPi
VERIFY_NOT_REACHED();
}
RefPtr<Gfx::FontCascadeList const> StyleComputer::compute_font_for_style_values(StyleValue const& font_family, CSSPixels const& font_size, StyleValue const& font_style, StyleValue const& font_weight, StyleValue const& font_stretch) const
RefPtr<Gfx::FontCascadeList const> StyleComputer::compute_font_for_style_values(StyleValue const& font_family, CSSPixels const& font_size, StyleValue const& font_style, double font_weight, StyleValue const& font_stretch) const
{
auto width = font_stretch.to_font_width();
auto weight = font_weight.to_font_weight();
// FIXME: We round to int here as that is what is expected by our font infrastructure below
auto weight = round_to<int>(font_weight);
auto slope = font_style.to_font_slope();
@ -1970,22 +1981,25 @@ void StyleComputer::compute_font(ComputedProperties& style, Optional<DOM::Abstra
compute_font_size(font_size_specified_value, style.math_depth(), inherited_font_size, inherited_math_depth, length_resolution_context),
style.is_property_inherited(PropertyID::FontSize) ? ComputedProperties::Inherited::Yes : ComputedProperties::Inherited::No);
auto inherited_font_weight = inheritance_parent_has_computed_properties ? inheritance_parent->computed_properties()->font_weight() : InitialValues::font_weight();
auto const& font_weight_specified_value = style.property(PropertyID::FontWeight);
style.set_property(
PropertyID::FontWeight,
compute_font_weight(font_weight_specified_value, inherited_font_weight, length_resolution_context),
style.is_property_inherited(PropertyID::FontWeight) ? ComputedProperties::Inherited::Yes : ComputedProperties::Inherited::No);
auto const& font_family = style.property(CSS::PropertyID::FontFamily);
auto const& font_style = style.property(CSS::PropertyID::FontStyle);
auto const& font_weight = style.property(CSS::PropertyID::FontWeight);
auto const& font_width = style.property(CSS::PropertyID::FontWidth);
auto font_list = compute_font_for_style_values(font_family, style.font_size(), font_style, font_weight, font_width);
auto font_list = compute_font_for_style_values(font_family, style.font_size(), font_style, style.font_weight(), font_width);
VERIFY(font_list);
VERIFY(!font_list->is_empty());
RefPtr<Gfx::Font const> const found_font = font_list->first();
style.set_property(
CSS::PropertyID::FontWeight,
NumberStyleValue::create(font_weight.to_font_weight()),
style.is_property_inherited(CSS::PropertyID::FontWeight) ? ComputedProperties::Inherited::Yes : ComputedProperties::Inherited::No);
style.set_computed_font_list(*font_list);
if (abstract_element.has_value() && is<HTML::HTMLHtmlElement>(abstract_element->element())) {
@ -3236,6 +3250,73 @@ NonnullRefPtr<StyleValue const> StyleComputer::compute_font_size(NonnullRefPtr<S
VERIFY_NOT_REACHED();
}
NonnullRefPtr<StyleValue const> StyleComputer::compute_font_weight(NonnullRefPtr<StyleValue const> const& specified_value, double inherited_font_weight, Length::ResolutionContext const& parent_length_resolution_context)
{
// https://drafts.csswg.org/css-fonts-4/#font-weight-prop
// a number, see below
// <number [1,1000]>
if (specified_value->is_number())
return specified_value;
// AD-HOC: Anywhere we support a numbers we should also support calcs
if (specified_value->is_calculated())
return NumberStyleValue::create(specified_value->as_calculated().resolve_number({ .length_resolution_context = parent_length_resolution_context }).value());
// normal
// Same as 400.
if (specified_value->to_keyword() == Keyword::Normal)
return NumberStyleValue::create(400);
// bold
// Same as 700.
if (specified_value->to_keyword() == Keyword::Bold)
return NumberStyleValue::create(700);
// Specified values of bolder and lighter indicate weights relative to the weight of the parent element. The
// computed weight is calculated based on the inherited font-weight value using the chart below.
//
// Inherited value (w) bolder lighter
// w < 100 400 No change
// 100 ≤ w < 350 400 100
// 350 ≤ w < 550 700 100
// 550 ≤ w < 750 900 400
// 750 ≤ w < 900 900 700
// 900 ≤ w No change 700
// bolder
// Specifies a bolder weight than the inherited value. See § 2.2.1 Relative Weights.
if (specified_value->to_keyword() == Keyword::Bolder) {
if (inherited_font_weight < 350)
return NumberStyleValue::create(400);
if (inherited_font_weight < 550)
return NumberStyleValue::create(700);
if (inherited_font_weight < 900)
return NumberStyleValue::create(900);
return NumberStyleValue::create(inherited_font_weight);
}
// lighter
// Specifies a lighter weight than the inherited value. See § 2.2.1 Relative Weights.
if (specified_value->to_keyword() == Keyword::Lighter) {
if (inherited_font_weight < 100)
return NumberStyleValue::create(inherited_font_weight);
if (inherited_font_weight < 550)
return NumberStyleValue::create(100);
if (inherited_font_weight < 750)
return NumberStyleValue::create(400);
return NumberStyleValue::create(700);
}
VERIFY_NOT_REACHED();
}
NonnullRefPtr<StyleValue const> StyleComputer::compute_opacity(NonnullRefPtr<StyleValue const> const& specified_value, PropertyValueComputationContext const& computation_context)
{
// https://drafts.csswg.org/css-color-4/#transparency