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LibWeb/CSS: Bring CSSNumericType algorithms up to date with spec

Browse source 
Took the opportunity to pull out a helper function for
entry_with_value_1_while_all_others_are_0(), too.

A couple of these require us to have extra contextual information about
what type percentages should resolve to. Until we have that available,
these are left as FIXMEs with a rough approximation.
This commit is contained in:
Sam Atkins 2024-12-17 15:31:38 +00:00 • committed by Andreas Kling
commit 8d40550478
Notes: github-actions[bot] 2024-12-21 17:15:27 +00:00
2 changed files with 73 additions and 71 deletions
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141
Libraries/LibWeb/CSS/CSSNumericType.cpp
View file

@ -131,7 +131,7 @@ Optional<CSSNumericType> CSSNumericType::added_to(CSSNumericType const& other) c
return {}; return {};
} }
// If type1 has a non-null percent hint hint and type2 doesn’t // If type1 has a non-null percent hint hint and type2 doesn’t
else if (type1.percent_hint().has_value() && !type2.percent_hint().has_value()) { if (type1.percent_hint().has_value() && !type2.percent_hint().has_value()) {
// Apply the percent hint hint to type2. // Apply the percent hint hint to type2.
type2.apply_percent_hint(type1.percent_hint().value()); type2.apply_percent_hint(type1.percent_hint().value());
} }
@ -154,7 +154,7 @@ Optional<CSSNumericType> CSSNumericType::added_to(CSSNumericType const& other) c
} }
// If type1 and/or type2 contain "percent" with a non-zero value, // If type1 and/or type2 contain "percent" with a non-zero value,
// and type1 and/or type2 contain a key other than "percent" with a non-zero value // and type1 and/or type2 contain a key other than "percent" with a non-zero value
else if ((type1.exponent(BaseType::Percent) != 0 || type2.exponent(BaseType::Percent) != 0) if ((type1.exponent(BaseType::Percent) != 0 || type2.exponent(BaseType::Percent) != 0)
&& (type1.contains_a_key_other_than_percent_with_a_non_zero_value() || type2.contains_a_key_other_than_percent_with_a_non_zero_value())) { && (type1.contains_a_key_other_than_percent_with_a_non_zero_value() || type2.contains_a_key_other_than_percent_with_a_non_zero_value())) {
// For each base type other than "percent" hint: // For each base type other than "percent" hint:
for (auto hint_int = 0; hint_int < to_underlying(BaseType::__Count); ++hint_int) { for (auto hint_int = 0; hint_int < to_underlying(BaseType::__Count); ++hint_int) {
@ -247,8 +247,9 @@ CSSNumericType CSSNumericType::inverted() const
{ {
// To invert a type type, perform the following steps: // To invert a type type, perform the following steps:
// 1. Let result be a new type with an initially empty ordered map and an initially null percent hint // 1. Let result be a new type with an initially empty ordered map and a percent hint matching that of type.
CSSNumericType result; CSSNumericType result;
result.set_percent_hint(percent_hint());
// 2. For each unit → exponent of type, set result[unit] to (-1 * exponent). // 2. For each unit → exponent of type, set result[unit] to (-1 * exponent).
for (auto i = 0; i < to_underlying(BaseType::__Count); ++i) { for (auto i = 0; i < to_underlying(BaseType::__Count); ++i) {
@ -299,20 +300,25 @@ Optional<CSSNumericType> CSSNumericType::made_consistent_with(CSSNumericType con
// https://drafts.css-houdini.org/css-typed-om-1/#apply-the-percent-hint // https://drafts.css-houdini.org/css-typed-om-1/#apply-the-percent-hint
void CSSNumericType::apply_percent_hint(BaseType hint) void CSSNumericType::apply_percent_hint(BaseType hint)
{ {
// To apply the percent hint hint to a type, perform the following steps: // To apply the percent hint hint to a type without a percent hint, perform the following steps:
VERIFY(!percent_hint().has_value());
// 1. If type doesn’t contain hint, set type[hint] to 0. // 1. Set type’s percent hint to hint.
set_percent_hint(hint);
// 2. If type doesn’t contain hint, set type[hint] to 0.
if (!exponent(hint).has_value()) if (!exponent(hint).has_value())
set_exponent(hint, 0); set_exponent(hint, 0);
// 2. If type contains "percent", add type["percent"] to type[hint], then set type["percent"] to 0. // 3. If hint is anything other than "percent", and type contains "percent",
if (exponent(BaseType::Percent).has_value()) { // add type["percent"] to type[hint], then set type["percent"] to 0.
if (hint != BaseType::Percent && exponent(BaseType::Percent).has_value()) {
set_exponent(hint, exponent(BaseType::Percent).value() + exponent(hint).value()); set_exponent(hint, exponent(BaseType::Percent).value() + exponent(hint).value());
set_exponent(BaseType::Percent, 0); set_exponent(BaseType::Percent, 0);
} }
// 3. Set type’s percent hint to hint. // 4. Return type.
set_percent_hint(hint); // FIXME: Is this needed? Nothing uses the value. https://github.com/w3c/css-houdini-drafts/issues/1135
} }
bool CSSNumericType::contains_all_the_non_zero_entries_of_other_with_the_same_value(CSSNumericType const& other) const bool CSSNumericType::contains_all_the_non_zero_entries_of_other_with_the_same_value(CSSNumericType const& other) const
@ -351,76 +357,82 @@ void CSSNumericType::copy_all_entries_from(CSSNumericType const& other, SkipIfAl
} }
} }
// https://drafts.css-houdini.org/css-typed-om-1/#cssnumericvalue-match Optional<CSSNumericType::BaseType> CSSNumericType::entry_with_value_1_while_all_others_are_0() const
bool CSSNumericType::matches_dimension(BaseType type) const
{ {
// A type matches <length> if its only non-zero entry is «[ "length" → 1 ]» and its percent hint is null. Optional<BaseType> result;
// Similarly for <angle>, <time>, <frequency>, <resolution>, and <flex>.
if (percent_hint().has_value())
return false;
for (auto i = 0; i < to_underlying(BaseType::__Count); ++i) { for (auto i = 0; i < to_underlying(BaseType::__Count); ++i) {
auto base_type = static_cast<BaseType>(i); auto base_type = static_cast<BaseType>(i);
auto type_exponent = exponent(base_type); auto type_exponent = exponent(base_type);
if (base_type == type) { if (type_exponent == 1) {
if (type_exponent != 1) if (result.has_value())
return false; return {};
} else { result = base_type;
if (type_exponent.has_value() && type_exponent != 0) } else if (type_exponent.has_value() && type_exponent != 0) {
return false; return {};
} }
} }
return result;
}
return true; // https://drafts.css-houdini.org/css-typed-om-1/#cssnumericvalue-match
bool CSSNumericType::matches_dimension(BaseType type) const
{
// A type matches <length> if its only non-zero entry is «[ "length" → 1 ]».
// Similarly for <angle>, <time>, <frequency>, <resolution>, and <flex>.
//
// If the context in which the value is used allows <percentage> values, and those percentages are resolved
// against another type, then for the type to be considered matching it must either have a null percent hint,
// or the percent hint must match the other type.
//
// If the context does not allow <percentage> values to be mixed with <length>/etc values (or doesn’t allow
// <percentage> values at all, such as border-width), then for the type to be considered matching the percent
// hint must be null.
// FIXME: Somehow we need to know what type percentages would be resolved against.
// I'm not at all sure if this check is correct.
if (percent_hint().has_value() && percent_hint() != type)
return false;
return entry_with_value_1_while_all_others_are_0() == type;
} }
// https://drafts.css-houdini.org/css-typed-om-1/#cssnumericvalue-match // https://drafts.css-houdini.org/css-typed-om-1/#cssnumericvalue-match
bool CSSNumericType::matches_percentage() const bool CSSNumericType::matches_percentage() const
{ {
// A type matches <percentage> if its only non-zero entry is «[ "percent" → 1 ]». // A type matches <percentage> if its only non-zero entry is «[ "percent" → 1 ]», and its percent hint is either
for (auto i = 0; i < to_underlying(BaseType::__Count); ++i) { // null or "percent".
auto base_type = static_cast<BaseType>(i); if (percent_hint().has_value() && percent_hint() != BaseType::Percent)
auto type_exponent = exponent(base_type);
if (base_type == BaseType::Percent) {
if (type_exponent != 1)
return false; return false;
} else {
if (type_exponent.has_value() && type_exponent != 0) return entry_with_value_1_while_all_others_are_0() == BaseType::Percent;
return false;
}
}
return true;
} }
// https://drafts.css-houdini.org/css-typed-om-1/#cssnumericvalue-match // https://drafts.css-houdini.org/css-typed-om-1/#cssnumericvalue-match
bool CSSNumericType::matches_dimension_percentage(BaseType type) const bool CSSNumericType::matches_dimension_percentage(BaseType type) const
{ {
// A type matches <length-percentage> if its only non-zero entry is either «[ "length" → 1 ]» // A type matches <length-percentage> if it matches <length> or matches <percentage>.
// or «[ "percent" → 1 ]» Same for <angle-percentage>, <time-percentage>, etc. // Same for <angle-percentage>, <time-percentage>, etc.
return matches_percentage() || matches_dimension(type);
// Check for percent -> 1 or type -> 1, but not both
if ((exponent(type) == 1) == (exponent(BaseType::Percent) == 1))
return false;
// Ensure all other types are absent or 0
for (auto i = 0; i < to_underlying(BaseType::__Count); ++i) {
auto base_type = static_cast<BaseType>(i);
auto type_exponent = exponent(base_type);
if (base_type == type || base_type == BaseType::Percent)
continue;
if (type_exponent.has_value() && type_exponent != 0)
return false;
}
return true;
} }
// https://drafts.css-houdini.org/css-typed-om-1/#cssnumericvalue-match // https://drafts.css-houdini.org/css-typed-om-1/#cssnumericvalue-match
bool CSSNumericType::matches_number() const bool CSSNumericType::matches_number() const
{ {
// A type matches <number> if it has no non-zero entries and its percent hint is null. // A type matches <number> if it has no non-zero entries.
//
// If the context in which the value is used allows <percentage> values, and those percentages are resolved
// against a type other than <number>, then for the type to be considered matching the percent hint must
// either be null or match the other type.
//
// If the context allows <percentage> values, but either doesn’t resolve them against another type or resolves
// them against a <number>, then for the type to be considered matching the percent hint must either be null
// or "percent".
//
// If the context does not allow <percentage> values, then for the type to be considered matching the percent
// hint must be null.
// FIXME: Somehow we need to know what type percentages would be resolved against.
// For now, just require no percent hint.
if (percent_hint().has_value()) if (percent_hint().has_value())
return false; return false;
@ -437,20 +449,9 @@ bool CSSNumericType::matches_number() const
// https://drafts.css-houdini.org/css-typed-om-1/#cssnumericvalue-match // https://drafts.css-houdini.org/css-typed-om-1/#cssnumericvalue-match
bool CSSNumericType::matches_number_percentage() const bool CSSNumericType::matches_number_percentage() const
{ {
// A type matches <number-percentage> if it has no non-zero entries, or its only non-zero entry is «[ "percent" → 1 ]». // FIXME: This is incorrect. <number-percentage> is not a legal type. Instead we should check separately if this
for (auto i = 0; i < to_underlying(BaseType::__Count); ++i) { // matches a number, or if it matches a percentage.
auto base_type = static_cast<BaseType>(i); return matches_number() || matches_percentage();
auto type_exponent = exponent(base_type);
if (base_type == BaseType::Percent) {
if (type_exponent.has_value() && type_exponent != 0 && type_exponent != 1)
return false;
} else if (type_exponent.has_value() && type_exponent != 0) {
return false;
}
}
return true;
} }
bool CSSNumericType::matches_dimension() const bool CSSNumericType::matches_dimension() const

1
Libraries/LibWeb/CSS/CSSNumericType.h
View file

@ -105,6 +105,7 @@ private:
}; };
void copy_all_entries_from(CSSNumericType const& other, SkipIfAlreadyPresent); void copy_all_entries_from(CSSNumericType const& other, SkipIfAlreadyPresent);
Optional<BaseType> entry_with_value_1_while_all_others_are_0() const;
bool matches_dimension(BaseType) const; bool matches_dimension(BaseType) const;
bool matches_dimension_percentage(BaseType) const; bool matches_dimension_percentage(BaseType) const;