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LibWeb: Add basic variable font support

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Integrates the new `FontVariationSettings` from LibGfx into LibWeb to
enable initial variable font functionality. Currently, only the `wght`
(weight) axis is fully supported and tested. This update also introduces
support for the CSS `font-variation-settings` property.
This commit is contained in:
norbiros 2025-10-14 16:21:00 +02:00 • committed by Alexander Kalenik
parent 489381698f
commit 3829a85fde
Notes: github-actions[bot] 2025-11-04 20:46:29 +00:00
7 changed files with 94 additions and 24 deletions
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64
Libraries/LibWeb/CSS/StyleComputer.cpp
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@ -229,14 +229,14 @@ bool FontLoader::is_loading() const
return m_fetch_controller && !m_vector_font;
}
RefPtr<Gfx::Font const> FontLoader::font_with_point_size(float point_size)
RefPtr<Gfx::Font const> FontLoader::font_with_point_size(float point_size, Gfx::FontVariationSettings const& variations)
{
if (!m_vector_font) {
if (!m_fetch_controller)
start_loading_next_url();
return nullptr;
}
return m_vector_font->font(point_size);
return m_vector_font->font(point_size, variations);
}
void FontLoader::start_loading_next_url()
@ -330,18 +330,18 @@ struct StyleComputer::MatchingFontCandidate {
FontFaceKey key;
Variant<FontLoaderList*, Gfx::Typeface const*> loader_or_typeface;
[[nodiscard]] RefPtr<Gfx::FontCascadeList const> font_with_point_size(float point_size) const
[[nodiscard]] RefPtr<Gfx::FontCascadeList const> font_with_point_size(float point_size, Gfx::FontVariationSettings const& variations) const
{
auto font_list = Gfx::FontCascadeList::create();
if (auto* loader_list = loader_or_typeface.get_pointer<FontLoaderList*>(); loader_list) {
for (auto const& loader : **loader_list) {
if (auto font = loader->font_with_point_size(point_size); font)
if (auto font = loader->font_with_point_size(point_size, variations); font)
font_list->add(*font, loader->unicode_ranges());
}
return font_list;
}
font_list->add(loader_or_typeface.get<Gfx::Typeface const*>()->font(point_size));
font_list->add(loader_or_typeface.get<Gfx::Typeface const*>()->font(point_size, variations));
return font_list;
}
};
@ -1668,27 +1668,27 @@ Length::FontMetrics StyleComputer::calculate_root_element_font_metrics(ComputedP
return font_metrics;
}
RefPtr<Gfx::FontCascadeList const> StyleComputer::find_matching_font_weight_ascending(Vector<MatchingFontCandidate> const& candidates, int target_weight, float font_size_in_pt, bool inclusive)
RefPtr<Gfx::FontCascadeList const> StyleComputer::find_matching_font_weight_ascending(Vector<MatchingFontCandidate> const& candidates, int target_weight, float font_size_in_pt, Gfx::FontVariationSettings const& variations, bool inclusive)
{
using Fn = AK::Function<bool(MatchingFontCandidate const&)>;
auto pred = inclusive ? Fn([&](auto const& matching_font_candidate) { return matching_font_candidate.key.weight >= target_weight; })
: Fn([&](auto const& matching_font_candidate) { return matching_font_candidate.key.weight > target_weight; });
auto it = find_if(candidates.begin(), candidates.end(), pred);
for (; it != candidates.end(); ++it) {
if (auto found_font = it->font_with_point_size(font_size_in_pt))
if (auto found_font = it->font_with_point_size(font_size_in_pt, variations))
return found_font;
}
return {};
}
RefPtr<Gfx::FontCascadeList const> StyleComputer::find_matching_font_weight_descending(Vector<MatchingFontCandidate> const& candidates, int target_weight, float font_size_in_pt, bool inclusive)
RefPtr<Gfx::FontCascadeList const> StyleComputer::find_matching_font_weight_descending(Vector<MatchingFontCandidate> const& candidates, int target_weight, float font_size_in_pt, Gfx::FontVariationSettings const& variations, bool inclusive)
{
using Fn = AK::Function<bool(MatchingFontCandidate const&)>;
auto pred = inclusive ? Fn([&](auto const& matching_font_candidate) { return matching_font_candidate.key.weight <= target_weight; })
: Fn([&](auto const& matching_font_candidate) { return matching_font_candidate.key.weight < target_weight; });
auto it = find_if(candidates.rbegin(), candidates.rend(), pred);
for (; it != candidates.rend(); ++it) {
if (auto found_font = it->font_with_point_size(font_size_in_pt))
if (auto found_font = it->font_with_point_size(font_size_in_pt, variations))
return found_font;
}
return {};
@ -1732,34 +1732,38 @@ RefPtr<Gfx::FontCascadeList const> StyleComputer::font_matching_algorithm(FlyStr
// If the desired weight is inclusively between 400 and 500, weights greater than or equal to the target weight
// are checked in ascending order until 500 is hit and checked, followed by weights less than the target weight
// in descending order, followed by weights greater than 500, until a match is found.
Gfx::FontVariationSettings variations;
variations.set_weight(weight);
if (weight >= 400 && weight <= 500) {
auto it = find_if(matching_family_fonts.begin(), matching_family_fonts.end(),
[&](auto const& matching_font_candidate) { return matching_font_candidate.key.weight >= weight; });
for (; it != matching_family_fonts.end() && it->key.weight <= 500; ++it) {
if (auto found_font = it->font_with_point_size(font_size_in_pt))
if (auto found_font = it->font_with_point_size(font_size_in_pt, variations))
return found_font;
}
if (auto found_font = find_matching_font_weight_descending(matching_family_fonts, weight, font_size_in_pt, false))
if (auto found_font = find_matching_font_weight_descending(matching_family_fonts, weight, font_size_in_pt, variations, false))
return found_font;
for (; it != matching_family_fonts.end(); ++it) {
if (auto found_font = it->font_with_point_size(font_size_in_pt))
if (auto found_font = it->font_with_point_size(font_size_in_pt, variations))
return found_font;
}
}
// If the desired weight is less than 400, weights less than or equal to the desired weight are checked in descending order
// followed by weights above the desired weight in ascending order until a match is found.
if (weight < 400) {
if (auto found_font = find_matching_font_weight_descending(matching_family_fonts, weight, font_size_in_pt, true))
if (auto found_font = find_matching_font_weight_descending(matching_family_fonts, weight, font_size_in_pt, variations, true))
return found_font;
if (auto found_font = find_matching_font_weight_ascending(matching_family_fonts, weight, font_size_in_pt, false))
if (auto found_font = find_matching_font_weight_ascending(matching_family_fonts, weight, font_size_in_pt, variations, false))
return found_font;
}
// If the desired weight is greater than 500, weights greater than or equal to the desired weight are checked in ascending order
// followed by weights below the desired weight in descending order until a match is found.
if (weight > 500) {
if (auto found_font = find_matching_font_weight_ascending(matching_family_fonts, weight, font_size_in_pt, true))
if (auto found_font = find_matching_font_weight_ascending(matching_family_fonts, weight, font_size_in_pt, variations, true))
return found_font;
if (auto found_font = find_matching_font_weight_descending(matching_family_fonts, weight, font_size_in_pt, false))
if (auto found_font = find_matching_font_weight_descending(matching_family_fonts, weight, font_size_in_pt, variations, false))
return found_font;
}
return {};
@ -1821,7 +1825,7 @@ 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, int slope, double font_weight, Percentage const& font_width) const
RefPtr<Gfx::FontCascadeList const> StyleComputer::compute_font_for_style_values(StyleValue const& font_family, CSSPixels const& font_size, int slope, double font_weight, Percentage const& font_width, HashMap<FlyString, NumberOrCalculated> const& font_variation_settings, Length::ResolutionContext const& length_resolution_context) const
{
// FIXME: We round to int here as that is what is expected by our font infrastructure below
auto width = round_to<int>(font_width.value());
@ -1842,10 +1846,32 @@ RefPtr<Gfx::FontCascadeList const> StyleComputer::compute_font_for_style_values(
auto result = Gfx::FontCascadeList::create();
if (auto it = m_loaded_fonts.find(key); it != m_loaded_fonts.end()) {
auto const& loaders = it->value;
Gfx::FontVariationSettings variation;
variation.set_weight(font_weight);
CalculationResolutionContext context {
.length_resolution_context = length_resolution_context,
};
for (auto const& [tag_string, value] : font_variation_settings) {
auto string_view = tag_string.bytes_as_string_view();
if (string_view.length() != 4)
continue;
auto tag = Gfx::FourCC(string_view.characters_without_null_termination());
auto resolved_value = value.resolved(context);
if (!resolved_value.has_value())
continue;
variation.axes.set(tag, resolved_value.release_value());
}
for (auto const& loader : loaders) {
if (auto found_font = loader->font_with_point_size(font_size_in_pt))
if (auto found_font = loader->font_with_point_size(font_size_in_pt, variation))
result->add(*found_font, loader->unicode_ranges());
}
return result;
}
@ -1984,7 +2010,7 @@ void StyleComputer::compute_font(ComputedProperties& style, Optional<DOM::Abstra
auto const& font_family = style.property(CSS::PropertyID::FontFamily);
auto font_list = compute_font_for_style_values(font_family, style.font_size(), style.font_slope(), style.font_weight(), style.font_width());
auto font_list = compute_font_for_style_values(font_family, style.font_size(), style.font_slope(), style.font_weight(), style.font_width(), style.font_variation_settings().value_or({}), font_computation_context.length_resolution_context);
VERIFY(font_list);
VERIFY(!font_list->is_empty());