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LibWeb/CSS: Implement "legacy value aliases" in generated code
This uses a `foo>bar` notation in the `valid-identifiers` field of Properties.json, to say "replace `foo` with `bar`". The motivation here is to avoid calling `parse_css_value_for_property()` inside the per-property switch in `parse_css_value()`. Eventually we'll need to be able to call that switch from `parse_css_value_for_properties()` so that shorthands can make use of any bespoke parsing code to parse their longhands.
This commit is contained in:
Sam Atkins
parent
062862f315
commit
943cc0e32a
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@ -19,22 +19,22 @@ Each property will have some set of these fields on it:
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(Note that required fields are not required on properties with `legacy-alias-for` or `logical-alias-for` set.)
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| Field | Required | Default | Description | Generated functions |
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|-----------------------------------|----------|---------|-------------------------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| `affects-layout` | No | `true` | Boolean. Whether changing this property will invalidate the element's layout. | `bool property_affects_layout(PropertyID)` |
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| `affects-stacking-context` | No | `false` | Boolean. Whether this property can cause a new stacking context for the element. | `bool property_affects_stacking_context(PropertyID)` |
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| `animation-type` | Yes | | String. How the property should be animated. Defined by the spec. See below. | `AnimationType animation_type_from_longhand_property(PropertyID)` |
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| `inherited` | Yes | | Boolean. Whether the property is inherited by its child elements. | `bool is_inherited_property(PropertyID)` |
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| `initial` | Yes | | String. The property's initial value if it is not specified. | `NonnullRefPtr<CSSStyleValue const> property_initial_value(PropertyID)` |
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| `legacy-alias-for` | No | Nothing | String. The name of a property this is an alias for. See below. | |
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| `logical-alias-for` | No | Nothing | An object. See below. | `bool property_is_logical_alias(PropertyID);`<br/>`PropertyID map_logical_alias_to_physical_property(PropertyID, LogicalAliasMappingContext const&)` |
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| `longhands` | No | `[]` | Array of strings. If this is a shorthand, these are the property names that it expands out into. | `Vector<PropertyID> longhands_for_shorthand(PropertyID)`<br/>`Vector<PropertyID> expanded_longhands_for_shorthand(PropertyID)`<br/>`Vector<PropertyID> shorthands_for_longhand(PropertyID)` |
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| `max-values` | No | `1` | Integer. How many values can be parsed for this property. eg, `margin` can have up to 4 values. | `size_t property_maximum_value_count(PropertyID)` |
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| `percentages-resolve-to` | No | Nothing | String. What type percentages get resolved to. eg, for `width` percentages are resolved to `length` values. | `Optional<ValueType> property_resolves_percentages_relative_to(PropertyID)` |
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| `positional-value-list-shorthand` | No | `false` | Boolean. Whether this property is a "positional value list shorthand". See below. | `bool property_is_positional_value_list_shorthand(PropertyID)` |
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| `quirks` | No | `[]` | Array of strings. Some properties have special behavior in "quirks mode", which are listed here. See below. | `bool property_has_quirk(PropertyID, Quirk)` |
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| `valid-identifiers` | No | `[]` | Array of strings. Which keywords the property accepts. Consider defining an enum instead and putting its name in the `valid-types` array. | `bool property_accepts_keyword(PropertyID, Keyword)` |
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| `valid-types` | No | `[]` | Array of strings. Which value types the property accepts. See below. | `bool property_accepts_type(PropertyID, ValueType)` |
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| Field | Required | Default | Description | Generated functions |
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|-----------------------------------|----------|---------|-------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| `affects-layout` | No | `true` | Boolean. Whether changing this property will invalidate the element's layout. | `bool property_affects_layout(PropertyID)` |
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| `affects-stacking-context` | No | `false` | Boolean. Whether this property can cause a new stacking context for the element. | `bool property_affects_stacking_context(PropertyID)` |
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| `animation-type` | Yes | | String. How the property should be animated. Defined by the spec. See below. | `AnimationType animation_type_from_longhand_property(PropertyID)` |
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| `inherited` | Yes | | Boolean. Whether the property is inherited by its child elements. | `bool is_inherited_property(PropertyID)` |
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| `initial` | Yes | | String. The property's initial value if it is not specified. | `NonnullRefPtr<CSSStyleValue const> property_initial_value(PropertyID)` |
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| `legacy-alias-for` | No | Nothing | String. The name of a property this is an alias for. See below. | |
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| `logical-alias-for` | No | Nothing | An object. See below. | `bool property_is_logical_alias(PropertyID);`<br/>`PropertyID map_logical_alias_to_physical_property(PropertyID, LogicalAliasMappingContext const&)` |
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| `longhands` | No | `[]` | Array of strings. If this is a shorthand, these are the property names that it expands out into. | `Vector<PropertyID> longhands_for_shorthand(PropertyID)`<br/>`Vector<PropertyID> expanded_longhands_for_shorthand(PropertyID)`<br/>`Vector<PropertyID> shorthands_for_longhand(PropertyID)` |
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| `max-values` | No | `1` | Integer. How many values can be parsed for this property. eg, `margin` can have up to 4 values. | `size_t property_maximum_value_count(PropertyID)` |
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| `percentages-resolve-to` | No | Nothing | String. What type percentages get resolved to. eg, for `width` percentages are resolved to `length` values. | `Optional<ValueType> property_resolves_percentages_relative_to(PropertyID)` |
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| `positional-value-list-shorthand` | No | `false` | Boolean. Whether this property is a "positional value list shorthand". See below. | `bool property_is_positional_value_list_shorthand(PropertyID)` |
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| `quirks` | No | `[]` | Array of strings. Some properties have special behavior in "quirks mode", which are listed here. See below. | `bool property_has_quirk(PropertyID, Quirk)` |
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| `valid-identifiers` | No | `[]` | Array of strings. Which keywords the property accepts. See below. | `bool property_accepts_keyword(PropertyID, Keyword)`<br/>`Optional<Keyword> resolve_legacy_value_alias(PropertyID, Keyword)` |
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| `valid-types` | No | `[]` | Array of strings. Which value types the property accepts. See below. | `bool property_accepts_type(PropertyID, ValueType)` |
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### `animation-type`
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@ -84,6 +84,14 @@ The [Quirks spec](https://quirks.spec.whatwg.org/#css) defines these.
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| The hashless hex color quirk | `hashless-hex-color` |
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| The unitless length quirk | `unitless-length` |
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### `valid-identifiers`
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A list of CSS keyword names, that the property accepts. Consider defining an enum instead and putting its name in the
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`valid-types` array, especially if the spec provides a name to a set of such keywords.
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Some properties have [legacy value aliases](https://drafts.csswg.org/css-cascade-5/#css-legacy-value-alias), where one
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keyword is parsed as another. These are supported as `"foo>bar"`, to make `foo` an alias for `bar`.
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### `valid-types`
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The `valid-types` array lists the names of CSS value types, as defined in the latest
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@ -140,6 +140,8 @@ Optional<Parser::PropertyAndValue> Parser::parse_css_value_for_properties(Readon
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if (keyword.has_value()) {
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if (auto property = any_property_accepts_keyword(property_ids, keyword.value()); property.has_value()) {
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tokens.discard_a_token();
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if (auto resolved_keyword = resolve_legacy_value_alias(property.value(), keyword.value()); resolved_keyword.has_value())
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return PropertyAndValue { *property, CSSKeywordValue::create(resolved_keyword.value()) };
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return PropertyAndValue { *property, CSSKeywordValue::create(keyword.value()) };
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}
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}
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@ -673,17 +675,6 @@ Parser::ParseErrorOr<NonnullRefPtr<CSSStyleValue const>> Parser::parse_css_value
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if (auto parsed_value = parse_overflow_value(tokens); parsed_value && !tokens.has_next_token())
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return parsed_value.release_nonnull();
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return ParseError::SyntaxError;
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case PropertyID::OverflowX:
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case PropertyID::OverflowY:
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if (auto parsed_value = parse_css_value_for_property(property_id, tokens); parsed_value && !tokens.has_next_token()) {
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// https://drafts.csswg.org/css-overflow-3/#valdef-overflow-overlay
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// User agents must also support the overlay keyword as a legacy value alias of auto.
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// FIXME: Figure out a generic way of supporting legacy value aliases.
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if (parsed_value->to_keyword() == Keyword::Overlay)
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return CSSKeywordValue::create(Keyword::Auto);
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return parsed_value.release_nonnull();
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}
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return ParseError::SyntaxError;
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case PropertyID::PlaceContent:
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if (auto parsed_value = parse_place_content_value(tokens); parsed_value && !tokens.has_next_token())
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return parsed_value.release_nonnull();
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@ -724,17 +715,6 @@ Parser::ParseErrorOr<NonnullRefPtr<CSSStyleValue const>> Parser::parse_css_value
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if (auto parsed_value = parse_text_decoration_line_value(tokens); parsed_value && !tokens.has_next_token())
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return parsed_value.release_nonnull();
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return ParseError::SyntaxError;
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case PropertyID::TextJustify:
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if (auto parsed_value = parse_css_value_for_property(property_id, tokens); parsed_value && !tokens.has_next_token()) {
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// https://drafts.csswg.org/css-text-3/#valdef-text-justify-distribute
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// For legacy reasons, UAs must also support the alternate keyword distribute which must compute to
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// inter-character, thus having the exact same meaning and behavior. UAs may treat this as a legacy value alias.
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// FIXME: Figure out a generic way of supporting legacy value aliases.
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if (parsed_value->to_keyword() == Keyword::Distribute)
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return CSSKeywordValue::create(Keyword::InterCharacter);
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return parsed_value.release_nonnull();
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}
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return ParseError::SyntaxError;
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case PropertyID::TextShadow:
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if (auto parsed_value = parse_shadow_value(tokens, AllowInsetKeyword::No); parsed_value && !tokens.has_next_token())
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return parsed_value.release_nonnull();
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@ -3622,24 +3602,11 @@ RefPtr<CSSStyleValue const> Parser::parse_opacity_value(PropertyID property_id,
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RefPtr<CSSStyleValue const> Parser::parse_overflow_value(TokenStream<ComponentValue>& tokens)
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{
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// https://drafts.csswg.org/css-overflow-3/#valdef-overflow-overlay
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// User agents must also support the overlay keyword as a legacy value alias of auto.
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// FIXME: Figure out a generic way of supporting legacy value aliases.
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// FIXME: Even better, make parsing the longhands go through their proper parsing routine.
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auto parse_an_overflow_longhand_value = [this](PropertyID property, auto& tokens) -> RefPtr<CSSStyleValue const> {
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auto maybe_value = parse_css_value_for_property(property, tokens);
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if (!maybe_value)
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return nullptr;
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if (maybe_value->to_keyword() == Keyword::Overlay)
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return CSSKeywordValue::create(Keyword::Auto);
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return maybe_value.release_nonnull();
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};
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auto transaction = tokens.begin_transaction();
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auto maybe_x_value = parse_an_overflow_longhand_value(PropertyID::OverflowX, tokens);
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auto maybe_x_value = parse_css_value_for_property(PropertyID::OverflowX, tokens);
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if (!maybe_x_value)
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return nullptr;
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auto maybe_y_value = parse_an_overflow_longhand_value(PropertyID::OverflowY, tokens);
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auto maybe_y_value = parse_css_value_for_property(PropertyID::OverflowY, tokens);
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transaction.commit();
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if (maybe_y_value) {
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return ShorthandStyleValue::create(PropertyID::Overflow,
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@ -2649,7 +2649,7 @@
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"overflow"
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],
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"valid-identifiers": [
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"overlay"
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"overlay>auto"
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]
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},
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"overflow-y": {
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@ -2660,7 +2660,7 @@
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"overflow"
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],
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"valid-identifiers": [
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"overlay"
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"overlay>auto"
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]
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},
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"padding": {
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@ -3163,7 +3163,7 @@
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"text-justify"
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],
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"valid-identifiers": [
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"distribute"
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"distribute>inter-character"
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]
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},
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"text-overflow": {
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@ -258,6 +258,7 @@ NonnullRefPtr<CSSStyleValue const> property_initial_value(PropertyID);
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bool property_accepts_type(PropertyID, ValueType);
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bool property_accepts_keyword(PropertyID, Keyword);
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Optional<Keyword> resolve_legacy_value_alias(PropertyID, Keyword);
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Optional<ValueType> property_resolves_percentages_relative_to(PropertyID);
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Vector<StringView> property_custom_ident_blacklist(PropertyID);
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@ -904,7 +905,7 @@ bool property_accepts_keyword(PropertyID property_id, Keyword keyword)
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{
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switch (property_id) {
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)~~~");
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properties.for_each_member([&](auto& name, auto& value) {
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properties.for_each_member([&](auto& name, JsonValue const& value) {
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VERIFY(value.is_object());
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auto& object = value.as_object();
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if (is_legacy_alias(object))
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@ -917,9 +918,15 @@ bool property_accepts_keyword(PropertyID property_id, Keyword keyword)
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if (auto maybe_valid_identifiers = object.get_array("valid-identifiers"sv); maybe_valid_identifiers.has_value() && !maybe_valid_identifiers->is_empty()) {
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property_generator.appendln(" switch (keyword) {");
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auto& valid_identifiers = maybe_valid_identifiers.value();
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for (auto& keyword : valid_identifiers.values()) {
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for (auto& keyword_value : valid_identifiers.values()) {
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auto keyword_generator = generator.fork();
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keyword_generator.set("keyword:titlecase", title_casify(keyword.as_string()));
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auto const& keyword_string = keyword_value.as_string();
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if (keyword_string.contains('>')) {
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auto parts = MUST(keyword_string.split_limit('>', 2));
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keyword_generator.set("keyword:titlecase", title_casify(parts[0]));
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} else {
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keyword_generator.set("keyword:titlecase", title_casify(keyword_string));
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}
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keyword_generator.appendln(" case Keyword::@keyword:titlecase@:");
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}
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property_generator.append(R"~~~(
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@ -956,6 +963,62 @@ bool property_accepts_keyword(PropertyID property_id, Keyword keyword)
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}
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}
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Optional<Keyword> resolve_legacy_value_alias(PropertyID property_id, Keyword keyword)
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{
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switch (property_id) {
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)~~~");
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properties.for_each_member([&](auto& name, JsonValue const& value) {
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VERIFY(value.is_object());
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auto& object = value.as_object();
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if (is_legacy_alias(object))
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return;
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if (auto maybe_valid_identifiers = object.get_array("valid-identifiers"sv); maybe_valid_identifiers.has_value() && !maybe_valid_identifiers->is_empty()) {
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auto& valid_identifiers = maybe_valid_identifiers.value();
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bool has_any_legacy_value_aliases = false;
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for (auto& keyword_value : valid_identifiers.values()) {
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if (keyword_value.as_string().contains('>')) {
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has_any_legacy_value_aliases = true;
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break;
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}
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}
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if (!has_any_legacy_value_aliases)
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return;
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auto property_generator = generator.fork();
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property_generator.set("name:titlecase", title_casify(name));
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property_generator.append(R"~~~(
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case PropertyID::@name:titlecase@:
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switch (keyword) {)~~~");
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for (auto& keyword_value : valid_identifiers.values()) {
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auto const& keyword_string = keyword_value.as_string();
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if (!keyword_string.contains('>'))
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continue;
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auto keyword_generator = generator.fork();
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auto parts = MUST(keyword_string.split_limit('>', 2));
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keyword_generator.set("from_keyword:titlecase", title_casify(parts[0]));
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keyword_generator.set("to_keyword:titlecase", title_casify(parts[1]));
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keyword_generator.append(R"~~~(
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case Keyword::@from_keyword:titlecase@:
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return Keyword::@to_keyword:titlecase@;)~~~");
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}
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property_generator.append(R"~~~(
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default:
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break;
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}
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break;
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)~~~");
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}
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});
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generator.append(R"~~~(
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default:
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break;
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}
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return {};
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}
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Optional<ValueType> property_resolves_percentages_relative_to(PropertyID property_id)
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{
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switch (property_id) {
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