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LibWeb: Understand the format() part of a @font-face's src

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This is used to skip downloading fonts in formats that we don't support.
Currently we only support TTF as far as I am aware.

The parts of a `src` are in a fixed order, unusually, which makes the
parsing more nesty instead of loopy.
This commit is contained in:
Sam Atkins 2022-03-31 21:18:54 +01:00 • committed by Andreas Kling
parent dbb0b68175
commit 12b8570ce3
4 changed files with 91 additions and 28 deletions
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113
Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp
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@ -4438,34 +4438,10 @@ RefPtr<CSSRule> Parser::parse_font_face_rule(TokenStream<ComponentValue>& tokens
continue;
}
if (declaration.name().equals_ignoring_case("src"sv)) {
Vector<FontFace::Source> supported_sources;
// FIXME: Implement `local()`.
// FIXME: Implement `format()`.
TokenStream token_stream { declaration.values() };
auto list_of_source_token_lists = parse_a_comma_separated_list_of_component_values(token_stream);
for (auto const& source_token_list : list_of_source_token_lists) {
Optional<AK::URL> url;
bool had_syntax_error = false;
for (auto const& source_token : source_token_list) {
// FIXME: Allow data urls for fonts.
if (auto maybe_url = parse_url_function(source_token); maybe_url.has_value()) {
if (url.has_value()) {
dbgln_if(CSS_PARSER_DEBUG, "CSSParser: @font-face src format invalid; discarding.");
had_syntax_error = true;
break;
}
url = maybe_url.release_value();
}
}
if (had_syntax_error)
continue;
if (!url.has_value())
continue;
supported_sources.empend(url.release_value());
}
if (supported_sources.is_empty())
continue;
src = move(supported_sources);
Vector<FontFace::Source> supported_sources = parse_font_face_src(token_stream);
if (!supported_sources.is_empty())
src = move(supported_sources);
continue;
}
if (declaration.name().equals_ignoring_case("unicode-range"sv)) {
@ -4506,6 +4482,89 @@ RefPtr<CSSRule> Parser::parse_font_face_rule(TokenStream<ComponentValue>& tokens
return CSSFontFaceRule::create(FontFace { font_family.release_value(), move(src), move(unicode_range) });
}
Vector<FontFace::Source> Parser::parse_font_face_src(TokenStream<ComponentValue>& component_values)
{
// FIXME: Get this information from the system somehow?
// Format-name table: https://www.w3.org/TR/css-fonts-4/#font-format-definitions
auto font_format_is_supported = [](StringView name) {
// The spec requires us to treat opentype and truetype as synonymous.
if (name.is_one_of_ignoring_case("opentype"sv, "truetype"sv))
return true;
return false;
};
Vector<FontFace::Source> supported_sources;
auto list_of_source_token_lists = parse_a_comma_separated_list_of_component_values(component_values);
for (auto const& source_token_list : list_of_source_token_lists) {
TokenStream source_tokens { source_token_list };
source_tokens.skip_whitespace();
auto& first = source_tokens.next_token();
// <url> [ format(<font-format>)]?
// FIXME: Allow data urls for fonts.
// FIXME: Implement optional tech() function from CSS-Fonts-4.
if (auto maybe_url = parse_url_function(first); maybe_url.has_value()) {
auto url = maybe_url.release_value();
Optional<FlyString> format;
source_tokens.skip_whitespace();
if (!source_tokens.has_next_token()) {
supported_sources.empend(move(url), format);
continue;
}
auto maybe_function = source_tokens.next_token();
if (!maybe_function.is_function()) {
dbgln_if(CSS_PARSER_DEBUG, "CSSParser: @font-face src invalid (token after `url()` that isn't a function: {}); discarding.", maybe_function.to_debug_string());
return {};
}
auto& function = maybe_function.function();
if (function.name().equals_ignoring_case("format"sv)) {
TokenStream format_tokens { function.values() };
format_tokens.skip_whitespace();
auto& format_name_token = format_tokens.next_token();
StringView format_name;
if (format_name_token.is(Token::Type::Ident)) {
format_name = format_name_token.token().ident();
} else if (format_name_token.is(Token::Type::String)) {
format_name = format_name_token.token().string();
} else {
dbgln_if(CSS_PARSER_DEBUG, "CSSParser: @font-face src invalid (`format()` parameter not an ident or string; is: {}); discarding.", format_name_token.to_debug_string());
return {};
}
if (!font_format_is_supported(format_name)) {
dbgln_if(CSS_PARSER_DEBUG, "CSSParser: @font-face src format({}) not supported; skipping.", format_name);
continue;
}
format = format_name;
} else {
dbgln_if(CSS_PARSER_DEBUG, "CSSParser: @font-face src invalid (unrecognized function token `{}`); discarding.", function.name());
return {};
}
source_tokens.skip_whitespace();
if (source_tokens.has_next_token()) {
dbgln_if(CSS_PARSER_DEBUG, "CSSParser: @font-face src invalid (extra token `{}`); discarding.", source_tokens.peek_token().to_debug_string());
return {};
}
supported_sources.empend(move(url), format);
continue;
} else {
// FIXME: Implement `local()`.
dbgln_if(CSS_PARSER_DEBUG, "CSSParser: @font-face src invalid (failed to parse url from: {}); discarding.", first.to_debug_string());
return {};
}
}
return supported_sources;
}
RefPtr<StyleValue> Parser::parse_list_style_value(Vector<ComponentValue> const& component_values)
{
if (component_values.size() > 3)