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ladybird/Libraries/LibWeb/CSS/FontComputer.cpp
Tim Ledbetter 77b9fcf7f9 LibWeb+LibWebView: Select generic font families based on requested style 
Pass the requested font weight and slope to generic_font_name() and use
them to select the most suitable font family. Families that have the
exact requested weight are strongly preferred, followed by families with
more style variety.

This ensures that when CSS requests bold text with a generic font family
like `serif`, we select a family that actually supports bold weights
rather than one that only has regular weight.

Co-authored-by: Jelle Raaijmakers <jelle@ladybird.org>
2026-03-24 15:08:24 +01:00

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/*
* Copyright (c) 2018-2025, Andreas Kling <andreas@ladybird.org>
* Copyright (c) 2021, the SerenityOS developers.
* Copyright (c) 2021-2025, Sam Atkins <sam@ladybird.org>
* Copyright (c) 2024, Matthew Olsson <mattco@serenityos.org>
* Copyright (c) 2025, Callum Law <callumlaw1709@outlook.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include "FontComputer.h"
#include <AK/NonnullRawPtr.h>
#include <LibGfx/Font/FontDatabase.h>
#include <LibGfx/Font/WOFF/Loader.h>
#include <LibGfx/Font/WOFF2/Loader.h>
#include <LibWeb/CSS/CSSFontFaceRule.h>
#include <LibWeb/CSS/CSSFontFeatureValuesRule.h>
#include <LibWeb/CSS/CSSStyleSheet.h>
#include <LibWeb/CSS/ComputedProperties.h>
#include <LibWeb/CSS/Fetch.h>
#include <LibWeb/CSS/FontFace.h>
#include <LibWeb/CSS/FontFaceSet.h>
#include <LibWeb/CSS/StyleValues/CustomIdentStyleValue.h>
#include <LibWeb/CSS/StyleValues/KeywordStyleValue.h>
#include <LibWeb/CSS/StyleValues/StringStyleValue.h>
#include <LibWeb/CSS/StyleValues/StyleValueList.h>
#include <LibWeb/DOM/Document.h>
#include <LibWeb/DOM/Element.h>
#include <LibWeb/DOM/ShadowRoot.h>
#include <LibWeb/Fetch/Infrastructure/HTTP/MIME.h>
#include <LibWeb/Fetch/Response.h>
#include <LibWeb/MimeSniff/Resource.h>
#include <LibWeb/Platform/FontPlugin.h>
namespace Web::CSS {
GC_DEFINE_ALLOCATOR(FontComputer);
GC_DEFINE_ALLOCATOR(FontLoader);
struct FontFaceKey {
NonnullRawPtr<FlyString const> family_name;
FontWeightRange weight;
int slope { 0 };
};
}
namespace AK {
namespace Detail {
template<>
inline constexpr bool IsHashCompatible<Web::CSS::FontFaceKey, Web::CSS::OwnFontFaceKey> = true;
template<>
inline constexpr bool IsHashCompatible<Web::CSS::OwnFontFaceKey, Web::CSS::FontFaceKey> = true;
}
template<>
struct Traits<Web::CSS::FontFaceKey> : public DefaultTraits<Web::CSS::FontFaceKey> {
static unsigned hash(Web::CSS::FontFaceKey const& key) { return pair_int_hash(key.family_name->hash(), pair_int_hash(key.weight.hash(), key.slope)); }
};
template<>
struct Traits<Web::CSS::OwnFontFaceKey> : public DefaultTraits<Web::CSS::OwnFontFaceKey> {
static unsigned hash(Web::CSS::OwnFontFaceKey const& key) { return key.hash(); }
};
template<>
struct Traits<Web::CSS::ComputedFontCacheKey> : public DefaultTraits<Web::CSS::ComputedFontCacheKey> {
static unsigned hash(Web::CSS::ComputedFontCacheKey const& key)
{
unsigned hash = 0;
for (auto const& family_value : key.font_family->as_value_list().values()) {
if (family_value->is_keyword())
hash = pair_int_hash(hash, to_underlying(family_value->as_keyword().keyword()));
else
hash = string_from_style_value(family_value).hash();
}
hash = pair_int_hash(hash, to_underlying(key.font_optical_sizing));
hash = pair_int_hash(hash, Traits<Web::CSSPixels>::hash(key.font_size));
hash = pair_int_hash(hash, key.font_slope);
hash = pair_int_hash(hash, Traits<double>::hash(key.font_weight));
hash = pair_int_hash(hash, Traits<double>::hash(key.font_width.value()));
for (auto const& [variation_name, variation_value] : key.font_variation_settings)
hash = pair_int_hash(hash, pair_int_hash(variation_name.hash(), Traits<double>::hash(variation_value)));
hash = pair_int_hash(hash, Traits<Web::CSS::FontFeatureData>::hash(key.font_feature_data));
return hash;
}
};
}
namespace Web::CSS {
OwnFontFaceKey::OwnFontFaceKey(FontFaceKey const& other)
: family_name(other.family_name)
, weight(other.weight)
, slope(other.slope)
{
}
OwnFontFaceKey::operator FontFaceKey() const
{
return FontFaceKey {
family_name,
weight,
slope
};
}
[[nodiscard]] bool OwnFontFaceKey::operator==(FontFaceKey const& other) const
{
return family_name == other.family_name
&& weight == other.weight
&& slope == other.slope;
}
FontLoader::FontLoader(FontComputer& font_computer, RuleOrDeclaration rule_or_declaration, FlyString family_name, Vector<Gfx::UnicodeRange> unicode_ranges, Vector<URL> urls, GC::Ptr<GC::Function<void(RefPtr<Gfx::Typeface const>)>> on_load)
: m_font_computer(font_computer)
, m_rule_or_declaration(rule_or_declaration)
, m_family_name(move(family_name))
, m_unicode_ranges(move(unicode_ranges))
, m_urls(move(urls))
, m_on_load(move(on_load))
{
}
FontLoader::~FontLoader() = default;
void FontLoader::visit_edges(Visitor& visitor)
{
Base::visit_edges(visitor);
visitor.visit(m_font_computer);
if (auto* rule = m_rule_or_declaration.value.get_pointer<RuleOrDeclaration::Rule>())
visitor.visit(rule->parent_style_sheet);
else if (auto* block = m_rule_or_declaration.value.get_pointer<RuleOrDeclaration::StyleDeclaration>())
visitor.visit(block->parent_rule);
visitor.visit(m_fetch_controller);
visitor.visit(m_on_load);
}
bool FontLoader::is_loading() const
{
return m_fetch_controller && !m_typeface;
}
RefPtr<Gfx::Font const> FontLoader::font_with_point_size(float point_size, Gfx::FontVariationSettings const& variations, Gfx::ShapeFeatures const& shape_features)
{
if (!m_typeface) {
if (!m_fetch_controller)
start_loading_next_url();
return nullptr;
}
return m_typeface->font(point_size, variations, shape_features);
}
void FontLoader::start_loading_next_url()
{
// FIXME: Load local() fonts somehow.
if (m_fetch_controller && m_fetch_controller->state() == Fetch::Infrastructure::FetchController::State::Ongoing)
return;
if (m_urls.is_empty())
return;
// https://drafts.csswg.org/css-fonts-4/#fetch-a-font
// To fetch a font given a selected <url> url for @font-face rule, fetch url, with ruleOrDeclaration being rule,
// destination "font", CORS mode "cors", and processResponse being the following steps given response res and null,
// failure or a byte stream stream:
m_fetch_controller = fetch_a_style_resource(m_urls.take_first(), m_rule_or_declaration, Fetch::Infrastructure::Request::Destination::Font, CorsMode::Cors,
[loader = this](auto response, auto stream) {
// 1. If stream is null, return.
// 2. Load a font from stream according to its type.
// NB: We need to fetch the next source if this one fails to fetch OR decode. So, first try to decode it.
RefPtr<Gfx::Typeface const> typeface;
if (auto* bytes = stream.template get_pointer<ByteBuffer>()) {
if (auto maybe_typeface = loader->try_load_font(response, *bytes); !maybe_typeface.is_error())
typeface = maybe_typeface.release_value();
}
if (!typeface) {
// NB: If we have other sources available, try the next one.
if (loader->m_urls.is_empty()) {
loader->font_did_load_or_fail(nullptr);
} else {
loader->m_fetch_controller = nullptr;
loader->start_loading_next_url();
}
} else {
loader->font_did_load_or_fail(move(typeface));
}
});
if (!m_fetch_controller)
font_did_load_or_fail(nullptr);
}
void FontLoader::font_did_load_or_fail(RefPtr<Gfx::Typeface const> typeface)
{
if (typeface) {
m_typeface = typeface.release_nonnull();
m_font_computer->clear_computed_font_cache(m_family_name);
if (m_on_load)
m_on_load->function()(m_typeface);
} else {
if (m_on_load)
m_on_load->function()(nullptr);
}
m_fetch_controller = nullptr;
}
ErrorOr<NonnullRefPtr<Gfx::Typeface const>> FontLoader::try_load_font(Fetch::Infrastructure::Response const& response, ByteBuffer const& bytes)
{
// FIXME: This could maybe use the format() provided in @font-face as well, since often the mime type is just application/octet-stream and we have to try every format
auto mime_type = Fetch::Infrastructure::extract_mime_type(response.header_list());
if (!mime_type.has_value() || !mime_type->is_font()) {
mime_type = MimeSniff::Resource::sniff(bytes, MimeSniff::SniffingConfiguration { .sniffing_context = MimeSniff::SniffingContext::Font });
}
if (mime_type.has_value()) {
if (mime_type->essence() == "font/ttf"sv || mime_type->essence() == "application/x-font-ttf"sv || mime_type->essence() == "font/otf"sv) {
if (auto result = Gfx::Typeface::try_load_from_temporary_memory(bytes); !result.is_error()) {
return result;
}
}
if (mime_type->essence() == "font/woff"sv || mime_type->essence() == "application/font-woff"sv) {
if (auto result = WOFF::try_load_from_bytes(bytes); !result.is_error()) {
return result;
}
}
if (mime_type->essence() == "font/woff2"sv || mime_type->essence() == "application/font-woff2"sv) {
if (auto result = WOFF2::try_load_from_bytes(bytes); !result.is_error()) {
return result;
}
}
}
return Error::from_string_literal("Automatic format detection failed");
}
struct FontComputer::MatchingFontCandidate {
FontFaceKey key;
Variant<FontLoaderList*, Gfx::Typeface const*> loader_or_typeface;
[[nodiscard]] RefPtr<Gfx::FontCascadeList const> font_with_point_size(float point_size, Gfx::FontVariationSettings const& variations, FontFeatureData const& font_feature_data, HashMap<FontFeatureValueKey, Vector<u32>> const& font_feature_values) const
{
auto const& shape_features = font_feature_data.to_shape_features(font_feature_values);
auto font_list = Gfx::FontCascadeList::create();
if (auto const* 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, variations, shape_features); font)
font_list->add(*font, loader->unicode_ranges());
}
return font_list;
}
font_list->add(loader_or_typeface.get<Gfx::Typeface const*>()->font(point_size, variations, shape_features));
return font_list;
}
};
void FontComputer::visit_edges(Visitor& visitor)
{
Base::visit_edges(visitor);
visitor.visit(m_document);
visitor.visit(m_loaded_fonts);
}
RefPtr<Gfx::FontCascadeList const> FontComputer::find_matching_font_weight_ascending(Vector<MatchingFontCandidate> const& candidates, int target_weight, float font_size_in_pt, Gfx::FontVariationSettings const& variations, FontFeatureData const& font_feature_data, HashMap<FontFeatureValueKey, Vector<u32>> const& font_feature_values, bool inclusive)
{
using Fn = AK::Function<bool(MatchingFontCandidate const&)>;
auto pred = inclusive ? Fn([&](auto const& matching_font_candidate) { return matching_font_candidate.key.weight.min >= target_weight; })
: Fn([&](auto const& matching_font_candidate) { return matching_font_candidate.key.weight.min > 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, variations, font_feature_data, font_feature_values))
return found_font;
}
return {};
}
RefPtr<Gfx::FontCascadeList const> FontComputer::find_matching_font_weight_descending(Vector<MatchingFontCandidate> const& candidates, int target_weight, float font_size_in_pt, Gfx::FontVariationSettings const& variations, FontFeatureData const& font_feature_data, HashMap<FontFeatureValueKey, Vector<u32>> const& font_feature_values, bool inclusive)
{
using Fn = AK::Function<bool(MatchingFontCandidate const&)>;
auto pred = inclusive ? Fn([&](auto const& matching_font_candidate) { return matching_font_candidate.key.weight.max <= target_weight; })
: Fn([&](auto const& matching_font_candidate) { return matching_font_candidate.key.weight.max < 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, variations, font_feature_data, font_feature_values))
return found_font;
}
return {};
}
// Partial implementation of the font-matching algorithm: https://www.w3.org/TR/css-fonts-4/#font-matching-algorithm
// FIXME: This should be replaced by the full CSS font selection algorithm.
RefPtr<Gfx::FontCascadeList const> FontComputer::font_matching_algorithm(FlyString const& family_name, int weight, int slope, float font_size_in_pt, Gfx::FontVariationSettings const& variations, FontFeatureData const& font_feature_data, HashMap<FontFeatureValueKey, Vector<u32>> const& font_feature_values) const
{
// If a font family match occurs, the user agent assembles the set of font faces in that family and then
// narrows the set to a single face using other font properties in the order given below.
Vector<MatchingFontCandidate> matching_family_fonts;
for (auto const& font_key_and_loader : m_loaded_fonts) {
if (font_key_and_loader.key.family_name.equals_ignoring_ascii_case(family_name))
matching_family_fonts.empend(font_key_and_loader.key, const_cast<FontLoaderList*>(&font_key_and_loader.value));
}
Gfx::FontDatabase::the().for_each_typeface_with_family_name(family_name, [&](Gfx::Typeface const& typeface) {
matching_family_fonts.empend(
FontFaceKey {
.family_name = typeface.family(),
// FIXME: Support system fonts that have a range of weights, etc.
.weight = { static_cast<int>(typeface.weight()), static_cast<int>(typeface.weight()) },
.slope = typeface.slope(),
},
&typeface);
});
if (matching_family_fonts.is_empty())
return {};
quick_sort(matching_family_fonts, [](auto const& a, auto const& b) {
return a.key.weight.min < b.key.weight.min;
});
// FIXME: 1. font-width is tried first.
// FIXME: 2. font-style is tried next.
// We don't have complete support of italic and oblique fonts, so matching on font-style can be simplified to:
// If a matching slope is found, all faces which don't have that matching slope are excluded from the matching set.
auto style_it = find_if(matching_family_fonts.begin(), matching_family_fonts.end(),
[&](auto const& matching_font_candidate) { return matching_font_candidate.key.slope == slope; });
if (style_it != matching_family_fonts.end()) {
matching_family_fonts.remove_all_matching([&](auto const& matching_font_candidate) {
return matching_font_candidate.key.slope != slope;
});
}
// 3. font-weight is matched next.
// If a font does not have any concept of varying strengths of weights, its weight is mapped according list in the
// property definition. If bolder/lighter relative weights are used, the effective weight is calculated based on
// the inherited weight value, as described in the definition of the font-weight property.
// FIXME: "varying strengths of weights"
// If the matching set after performing the steps above includes faces with weight values containing the
// font-weight desired value, faces with weight values which do not include the desired font-weight value are
// removed from the matching set.
// FIXME: This whole function currently just returns the first match instead of progressing further, so we'll do that here too.
auto matching_weight_it = matching_family_fonts.find_if([weight](auto const& candidate) {
return candidate.key.weight.contains_inclusive(weight);
});
for (; matching_weight_it != matching_family_fonts.end(); ++matching_weight_it) {
if (auto found_font = matching_weight_it->font_with_point_size(font_size_in_pt, variations, font_feature_data, font_feature_values))
return found_font;
}
// If there is no face which contains the desired value, a weight value is chosen using the rules below:
// - 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.
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.min >= weight; });
for (; it != matching_family_fonts.end() && it->key.weight.min <= 500; ++it) {
if (auto found_font = it->font_with_point_size(font_size_in_pt, variations, font_feature_data, font_feature_values))
return found_font;
}
if (auto found_font = find_matching_font_weight_descending(matching_family_fonts, weight, font_size_in_pt, variations, font_feature_data, font_feature_values, false))
return found_font;
for (; it != matching_family_fonts.end(); ++it) {
if (auto found_font = it->font_with_point_size(font_size_in_pt, variations, font_feature_data, font_feature_values))
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, variations, font_feature_data, font_feature_values, true))
return found_font;
if (auto found_font = find_matching_font_weight_ascending(matching_family_fonts, weight, font_size_in_pt, variations, font_feature_data, font_feature_values, 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, variations, font_feature_data, font_feature_values, true))
return found_font;
if (auto found_font = find_matching_font_weight_descending(matching_family_fonts, weight, font_size_in_pt, variations, font_feature_data, font_feature_values, false))
return found_font;
}
VERIFY_NOT_REACHED();
}
HashMap<FontFeatureValueKey, Vector<u32>> const& FontComputer::font_feature_values_for_family(FlyString const& family_name) const
{
return m_font_feature_values_cache.ensure(family_name, [&]() {
HashMap<FontFeatureValueKey, Vector<u32>> font_feature_values;
// https://drafts.csswg.org/css-fonts/#font-feature-values-syntax
// For each <family-name> in the @font-feature-values prelude, each font feature value declaration defines a
// mapping between a (family name, feature block name, declaration name) tuple and the list of one or more
// integers from the declaration’s value. If the same tuple appears more than once in a document (such as if a
// single block), the last-defined one is used.
// FIXME: We only account for Author stylesheets here, we should also account for UserAgent and User
m_document->style_scope().for_each_active_css_style_sheet([&](CSS::CSSStyleSheet const& sheet) {
// FIXME: Account for @font-feature-values within grouping (i.e. @media, @supports) rules as well.
for (auto const& rule : sheet.rules()) {
if (auto const* font_feature_values_rule = as_if<CSSFontFeatureValuesRule>(*rule)) {
if (!font_feature_values_rule->font_families().contains_slow(family_name))
continue;
font_feature_values.update(font_feature_values_rule->to_hash_map());
}
}
});
return font_feature_values;
});
return m_font_feature_values_cache.get(family_name).value();
}
NonnullRefPtr<Gfx::FontCascadeList const> FontComputer::compute_font_for_style_values(StyleValue const& font_family, CSSPixels const& font_size, int font_slope, double font_weight, Percentage const& font_width, FontOpticalSizing font_optical_sizing, HashMap<FlyString, double> const& font_variation_settings, FontFeatureData const& font_feature_data) const
{
ComputedFontCacheKey cache_key {
.font_family = font_family,
.font_optical_sizing = font_optical_sizing,
.font_size = font_size,
.font_slope = font_slope,
.font_weight = font_weight,
.font_width = font_width,
.font_variation_settings = font_variation_settings,
.font_feature_data = font_feature_data,
};
return m_computed_font_cache.ensure(cache_key, [&]() {
return compute_font_for_style_values_impl(font_family, font_size, font_slope, font_weight, font_width, font_optical_sizing, font_variation_settings, font_feature_data);
});
}
NonnullRefPtr<Gfx::FontCascadeList const> FontComputer::compute_font_for_style_values_impl(StyleValue const& font_family, CSSPixels const& font_size, int slope, double font_weight, Percentage const& font_width, FontOpticalSizing font_optical_sizing, HashMap<FlyString, double> const& font_variation_settings, FontFeatureData const& font_feature_data) const
{
// FIXME: We round to int here as that is what is expected by our font infrastructure below
auto weight = round_to<int>(font_weight);
// FIXME: We need to respect `font-size-adjust` once that is implemented.
auto font_size_used_value = font_size.to_float();
Gfx::FontVariationSettings variation;
variation.set_weight(font_weight);
variation.set_width(font_width.value());
// NB: The spec recommends that we use the 'used value' of font-size for 'opsz' when font-optical-sizing is 'auto'.
// FIXME: User agents must not select a value for the "opsz" axis which is not supported by the font used for
// rendering the text. This can be accomplished by clamping a chosen value to the range supported by the
// font. https://drafts.csswg.org/css-fonts/#font-optical-sizing-def
if (font_optical_sizing == FontOpticalSizing::Auto)
variation.set_optical_sizing(font_size_used_value);
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());
variation.axes.set(tag, value);
}
// FIXME: Implement the full font-matching algorithm: https://www.w3.org/TR/css-fonts-4/#font-matching-algorithm
float const font_size_in_pt = font_size_used_value * 0.75f;
auto find_font = [&](FlyString const& family) -> RefPtr<Gfx::FontCascadeList const> {
auto const& font_feature_values = font_feature_values_for_family(family);
// OPTIMIZATION: Look for an exact match in loaded fonts first.
// FIXME: Respect the other font-* descriptors
FontFaceKey key {
.family_name = family,
.weight = { weight, weight },
.slope = slope,
};
if (auto it = m_loaded_fonts.find(key); it != m_loaded_fonts.end()) {
auto result = Gfx::FontCascadeList::create();
auto const& loaders = it->value;
for (auto const& loader : loaders) {
auto shape_features = font_feature_data.to_shape_features(font_feature_values);
if (auto found_font = loader->font_with_point_size(font_size_in_pt, variation, shape_features))
result->add(*found_font, loader->unicode_ranges());
}
return result;
}
if (auto found_font = font_matching_algorithm(family, weight, slope, font_size_in_pt, variation, font_feature_data, font_feature_values); found_font && !found_font->is_empty())
return found_font;
return {};
};
auto find_generic_font = [&](Keyword font_id) -> RefPtr<Gfx::FontCascadeList const> {
Platform::GenericFont generic_font {};
switch (font_id) {
case Keyword::Monospace:
case Keyword::UiMonospace:
generic_font = Platform::GenericFont::Monospace;
break;
case Keyword::Serif:
generic_font = Platform::GenericFont::Serif;
break;
case Keyword::Fantasy:
generic_font = Platform::GenericFont::Fantasy;
break;
case Keyword::SansSerif:
generic_font = Platform::GenericFont::SansSerif;
break;
case Keyword::Cursive:
generic_font = Platform::GenericFont::Cursive;
break;
case Keyword::UiSerif:
generic_font = Platform::GenericFont::UiSerif;
break;
case Keyword::UiSansSerif:
generic_font = Platform::GenericFont::UiSansSerif;
break;
case Keyword::UiRounded:
generic_font = Platform::GenericFont::UiRounded;
break;
default:
return {};
}
return find_font(Platform::FontPlugin::the().generic_font_name(generic_font, weight, slope));
};
auto font_list = Gfx::FontCascadeList::create();
for (auto const& family : font_family.as_value_list().values()) {
RefPtr<Gfx::FontCascadeList const> other_font_list;
if (family->is_keyword()) {
other_font_list = find_generic_font(family->to_keyword());
} else {
other_font_list = find_font(string_from_style_value(family));
}
if (other_font_list)
font_list->extend(*other_font_list);
}
// NB: @font-feature-values can't apply to the default font since it's not loaded from CSS
auto default_font = Platform::FontPlugin::the().default_font(font_size_in_pt, variation, font_feature_data.to_shape_features({}));
if (font_list->is_empty()) {
// This is needed to make sure we check default font before reaching to emojis.
font_list->add(*default_font);
}
// Add emoji and symbol fonts
for (auto font_name : Platform::FontPlugin::the().symbol_font_names()) {
if (auto other_font_list = find_font(font_name)) {
font_list->extend(*other_font_list);
}
}
// The default font is already included in the font list, but we explicitly set it
// as the last-resort font. This ensures that if none of the specified fonts contain
// the requested code point, there is still a font available to provide a fallback glyph.
font_list->set_last_resort_font(*default_font);
if (!Platform::FontPlugin::the().is_layout_test_mode()) {
font_list->set_system_font_fallback_callback([](u32 code_point, Gfx::Font const& reference_font) -> RefPtr<Gfx::Font const> {
return Gfx::FontDatabase::the().get_font_for_code_point(
code_point,
reference_font.point_size(),
reference_font.weight(),
reference_font.typeface().width(),
reference_font.slope());
});
}
return font_list;
}
Gfx::Font const& FontComputer::initial_font() const
{
// FIXME: This is not correct.
static auto font = ComputedProperties::font_fallback(false, false, 12);
return font;
}
static bool style_value_references_font_family(StyleValue const& font_family_value, FlyString const& family_name)
{
if (!font_family_value.is_value_list())
return false;
for (auto const& item : font_family_value.as_value_list().values()) {
if (item->is_keyword())
continue; // Skip generic keywords (monospace, serif, etc.)
FlyString item_family_name = string_from_style_value(*item);
if (item_family_name.equals_ignoring_ascii_case(family_name))
return true;
}
return false;
}
void FontComputer::clear_computed_font_cache(FlyString const& family_name)
{
// Only clear cache entries that reference the loaded font family.
m_computed_font_cache.remove_all_matching([&](auto const& key, auto const&) {
return style_value_references_font_family(key.font_family, family_name);
});
auto element_uses_font_family = [&](DOM::Element const& element) {
// Check the element's own font-family.
if (auto style = element.computed_properties()) {
if (style_value_references_font_family(style->property(PropertyID::FontFamily), family_name))
return true;
}
// Check pseudo-elements, which may use a different font-family than the element itself.
for (size_t i = 0; i < to_underlying(PseudoElement::KnownPseudoElementCount); ++i) {
if (auto style = element.computed_properties(static_cast<PseudoElement>(i))) {
if (style_value_references_font_family(style->property(PropertyID::FontFamily), family_name))
return true;
}
}
return false;
};
if (document().needs_full_style_update())
return;
// Walk the DOM tree (including shadow trees) and invalidate elements that use this font family.
document().for_each_shadow_including_inclusive_descendant([&](DOM::Node& node) {
auto* element = as_if<DOM::Element>(node);
if (!element)
return TraversalDecision::Continue;
// If this element's subtree is already marked for style update, skip the entire subtree.
if (element->entire_subtree_needs_style_update())
return TraversalDecision::SkipChildrenAndContinue;
// If this element already needs a style update, check descendants but don't re-check this element.
if (element->needs_style_update())
return TraversalDecision::Continue;
if (element_uses_font_family(*element)) {
element->set_needs_style_update(true);
return TraversalDecision::Continue;
}
return TraversalDecision::Continue;
});
}
void FontComputer::clear_font_feature_values_cache(FlyString const& family_name)
{
m_font_feature_values_cache.remove(family_name);
}
GC::Ptr<FontLoader> FontComputer::load_font_face(ParsedFontFace const& font_face, GC::Ptr<GC::Function<void(RefPtr<Gfx::Typeface const>)>> on_load)
{
if (font_face.sources().is_empty()) {
if (on_load)
on_load->function()({});
return {};
}
FontFaceKey key {
.family_name = font_face.font_family(),
.weight = font_face.weight().value_or({ 0, 0 }),
.slope = font_face.slope().value_or(0),
};
// FIXME: Handle local() font sources.
Vector<URL> urls;
for (auto const& source : font_face.sources()) {
if (source.local_or_url.has<URL>())
urls.append(source.local_or_url.get<URL>());
}
if (urls.is_empty()) {
if (on_load)
on_load->function()({});
return {};
}
RuleOrDeclaration rule_or_declaration {
.environment_settings_object = document().relevant_settings_object(),
.value = RuleOrDeclaration::Rule {
.parent_style_sheet = font_face.parent_rule()->parent_style_sheet(),
}
};
auto loader = heap().allocate<FontLoader>(*this, rule_or_declaration, font_face.font_family(), font_face.unicode_ranges(), move(urls), move(on_load));
auto& loader_ref = *loader;
auto maybe_font_loaders_list = m_loaded_fonts.get(key);
if (maybe_font_loaders_list.has_value()) {
maybe_font_loaders_list->append(move(loader));
} else {
FontLoaderList loaders;
loaders.append(loader);
m_loaded_fonts.set(OwnFontFaceKey(key), move(loaders));
}
// Actual object owned by font loader list inside m_loaded_fonts, this isn't use-after-move/free
return loader_ref;
}
void FontComputer::load_fonts_from_sheet(CSSStyleSheet& sheet)
{
// FIXME: Handle @font-face and @font-feature-values within grouping rules (@media, @supports, etc)
for (auto const& rule : sheet.rules()) {
if (auto* font_face_rule = as_if<CSSFontFaceRule>(*rule)) {
if (!font_face_rule->is_valid())
continue;
auto font_face = FontFace::create_css_connected(document().realm(), *font_face_rule);
document().fonts()->add_css_connected_font(font_face);
// NB: Load via FontFace::load(), to satisfy this requirement:
// https://drafts.csswg.org/css-font-loading/#font-face-load
// User agents can initiate font loads on their own, whenever they determine that a given font face is
// necessary to render something on the page. When this happens, they must act as if they had called the
// corresponding FontFace’s load() method described here.
font_face->load();
}
if (auto* font_feature_values_rule = as_if<CSSFontFeatureValuesRule>(*rule))
font_feature_values_rule->clear_caches();
}
}
void FontComputer::unload_fonts_from_sheet(CSSStyleSheet& sheet)
{
// FIXME: Handle @font-face and @font-feature-values within grouping rules (@media, @supports, etc)
for (auto& [_, font_loader_list] : m_loaded_fonts) {
font_loader_list.remove_all_matching([&](auto& font_loader) {
return sheet.has_associated_font_loader(*font_loader);
});
}
// https://drafts.csswg.org/css-font-loading/#font-face-css-connection
// If a @font-face rule is removed from the document, its connected FontFace object is no longer CSS-connected.
for (auto const& rule : sheet.rules()) {
if (auto* font_face_rule = as_if<CSSFontFaceRule>(*rule))
font_face_rule->disconnect_font_face();
if (auto* font_feature_values_rule = as_if<CSSFontFeatureValuesRule>(*rule))
font_feature_values_rule->clear_caches();
}
}
}
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