style: Add support for parsing of the CSS text-underline-position property.

Differential Revision: https://phabricator.services.mozilla.com/D54722

components/style/properties/counted_unknown_properties.py

@@ -10,7 +10,8 @@
 #    "offset-distance",
 #    "offset-path",
 #    "offset-rotate",
-#    "offset"
+#    "offset",
+#    "text-underline-position",
 COUNTED_UNKNOWN_PROPERTIES = [
     "-webkit-font-smoothing",
     "-webkit-tap-highlight-color",
@@ -40,7 +41,6 @@ COUNTED_UNKNOWN_PROPERTIES = [
     "baseline-shift",
     "-webkit-hyphenate-character",
     "page",
-    "text-underline-position",
     "-webkit-highlight",
     "background-repeat-x",
     "-webkit-padding-end",

components/style/properties/data.py

@@ -385,6 +385,7 @@ class Longhand(object):
                 "TextDecorationLine",
                 "TextEmphasisPosition",
                 "TextTransform",
+                "TextUnderlinePosition",
                 "TouchAction",
                 "TransformStyle",
                 "UserSelect",

components/style/properties/longhands/inherited_text.mako.rs

@@ -391,6 +391,18 @@ ${helpers.predefined_type(
     spec="https://drafts.csswg.org/css-text-decor-4/#underline-offset",
 )}
 
+// text underline position
+${helpers.predefined_type(
+    "text-underline-position",
+    "TextUnderlinePosition",
+    "computed::TextUnderlinePosition::AUTO",
+    engines="gecko",
+    animation_value_type="discrete",
+    gecko_pref="layout.css.text-underline-position.enabled",
+    has_effect_on_gecko_scrollbars=False,
+    spec="https://drafts.csswg.org/css-text-decor-3/#text-underline-position-property",
+)}
+
 // text decoration skip ink
 ${helpers.predefined_type(
     "text-decoration-skip-ink",

components/style/values/computed/mod.rs

@@ -79,6 +79,7 @@ pub use self::text::{InitialLetter, LetterSpacing, LineBreak, LineHeight};
 pub use self::text::{OverflowWrap, TextOverflow, WordBreak, WordSpacing};
 pub use self::text::{TextAlign, TextEmphasisPosition, TextEmphasisStyle};
 pub use self::text::{TextDecorationLength, TextDecorationSkipInk};
+pub use self::text::TextUnderlinePosition;
 pub use self::time::Time;
 pub use self::transform::{Rotate, Scale, Transform, TransformOperation};
 pub use self::transform::{TransformOrigin, TransformStyle, Translate};

components/style/values/computed/text.rs

@@ -22,6 +22,7 @@ pub use crate::values::specified::TextAlignKeyword as TextAlign;
 pub use crate::values::specified::{LineBreak, OverflowWrap, WordBreak};
 pub use crate::values::specified::{TextDecorationLine, TextEmphasisPosition};
 pub use crate::values::specified::{TextDecorationSkipInk, TextTransform};
+pub use crate::values::specified::TextUnderlinePosition;
 
 /// A computed value for the `initial-letter` property.
 pub type InitialLetter = GenericInitialLetter<CSSFloat, CSSInteger>;

components/style/values/specified/mod.rs

@@ -84,6 +84,7 @@ pub use self::text::{InitialLetter, LetterSpacing, LineBreak, LineHeight, TextAl
 pub use self::text::{OverflowWrap, TextEmphasisPosition, TextEmphasisStyle, WordBreak};
 pub use self::text::{TextAlignKeyword, TextDecorationLine, TextOverflow, WordSpacing};
 pub use self::text::{TextDecorationLength, TextDecorationSkipInk, TextTransform};
+pub use self::text::TextUnderlinePosition;
 pub use self::time::Time;
 pub use self::transform::{Rotate, Scale, Transform};
 pub use self::transform::{TransformOrigin, TransformStyle, Translate};

components/style/values/specified/text.rs

@@ -1054,3 +1054,98 @@ impl TextDecorationLength {
         matches!(*self, GenericTextDecorationLength::Auto)
     }
 }
+
+bitflags! {
+    #[derive(MallocSizeOf, SpecifiedValueInfo, ToComputedValue, ToResolvedValue, ToShmem)]
+    #[value_info(other_values = "auto,under,left,right")]
+    #[repr(C)]
+    /// Specified keyword values for the text-underline-position property.
+    /// (Non-exclusive, but not all combinations are allowed: only `under` may occur
+    /// together with either `left` or `right`.)
+    /// https://drafts.csswg.org/css-text-decor-3/#text-underline-position-property
+    pub struct TextUnderlinePosition: u8 {
+        /// Use automatic positioning below the alphabetic baseline.
+        const AUTO = 0;
+        /// Below the glyph box.
+        const UNDER = 1 << 0;
+        /// In vertical mode, place to the left of the text.
+        const LEFT = 1 << 1;
+        /// In vertical mode, place to the right of the text.
+        const RIGHT = 1 << 2;
+    }
+}
+
+impl Parse for TextUnderlinePosition {
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<TextUnderlinePosition, ParseError<'i>> {
+        let mut result = TextUnderlinePosition::empty();
+
+        loop {
+            let location = input.current_source_location();
+            let ident = match input.next() {
+                Ok(&Token::Ident(ref ident)) => ident,
+                Ok(other) => return Err(location.new_unexpected_token_error(other.clone())),
+                Err(..) => break,
+            };
+
+            match_ignore_ascii_case! { ident,
+                "auto" if result.is_empty() => {
+                    return Ok(result);
+                },
+                "under" if !result.intersects(TextUnderlinePosition::UNDER) => {
+                    result.insert(TextUnderlinePosition::UNDER);
+                },
+                "left" if !result.intersects(TextUnderlinePosition::LEFT |
+                                             TextUnderlinePosition::RIGHT) => {
+                    result.insert(TextUnderlinePosition::LEFT);
+                },
+                "right" if !result.intersects(TextUnderlinePosition::LEFT |
+                                              TextUnderlinePosition::RIGHT) => {
+                    result.insert(TextUnderlinePosition::RIGHT);
+                },
+                _ => return Err(location.new_custom_error(
+                    SelectorParseErrorKind::UnexpectedIdent(ident.clone())
+                )),
+            }
+        }
+
+        if !result.is_empty() {
+            Ok(result)
+        } else {
+            Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+        }
+    }
+}
+
+impl ToCss for TextUnderlinePosition {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        if self.is_empty() {
+            return dest.write_str("auto");
+        }
+
+        let mut writer = SequenceWriter::new(dest, " ");
+        let mut any = false;
+
+        macro_rules! maybe_write {
+            ($ident:ident => $str:expr) => {
+                if self.contains(TextUnderlinePosition::$ident) {
+                    any = true;
+                    writer.raw_item($str)?;
+                }
+            };
+        }
+
+        maybe_write!(UNDER => "under");
+        maybe_write!(LEFT => "left");
+        maybe_write!(RIGHT => "right");
+
+        debug_assert!(any);
+
+        Ok(())
+    }
+}