Vendor things

third-party/vendor/ttf-parser/src/ggg/chained_context.rs

@@ -0,0 +1,135 @@
+use super::{ClassDefinition, Coverage, SequenceLookupRecord};
+use crate::parser::{FromSlice, LazyArray16, LazyOffsetArray16, Stream};
+
+/// A [Chained Contextual Lookup Subtable](
+/// https://docs.microsoft.com/en-us/typography/opentype/spec/chapter2#chseqctxt1).
+#[allow(missing_docs)]
+#[derive(Clone, Copy, Debug)]
+pub enum ChainedContextLookup<'a> {
+    /// Simple glyph contexts.
+    Format1 {
+        coverage: Coverage<'a>,
+        sets: ChainedSequenceRuleSets<'a>,
+    },
+    /// Class-based glyph contexts.
+    Format2 {
+        coverage: Coverage<'a>,
+        backtrack_classes: ClassDefinition<'a>,
+        input_classes: ClassDefinition<'a>,
+        lookahead_classes: ClassDefinition<'a>,
+        sets: ChainedSequenceRuleSets<'a>,
+    },
+    /// Coverage-based glyph contexts.
+    Format3 {
+        coverage: Coverage<'a>,
+        backtrack_coverages: LazyOffsetArray16<'a, Coverage<'a>>,
+        input_coverages: LazyOffsetArray16<'a, Coverage<'a>>,
+        lookahead_coverages: LazyOffsetArray16<'a, Coverage<'a>>,
+        lookups: LazyArray16<'a, SequenceLookupRecord>,
+    },
+}
+
+impl<'a> ChainedContextLookup<'a> {
+    pub(crate) fn parse(data: &'a [u8]) -> Option<Self> {
+        let mut s = Stream::new(data);
+        match s.read::<u16>()? {
+            1 => {
+                let coverage = Coverage::parse(s.read_at_offset16(data)?)?;
+                let count = s.read::<u16>()?;
+                let offsets = s.read_array16(count)?;
+                Some(Self::Format1 {
+                    coverage,
+                    sets: ChainedSequenceRuleSets::new(data, offsets),
+                })
+            }
+            2 => {
+                let coverage = Coverage::parse(s.read_at_offset16(data)?)?;
+                let backtrack_classes = ClassDefinition::parse(s.read_at_offset16(data)?)?;
+                let input_classes = ClassDefinition::parse(s.read_at_offset16(data)?)?;
+                let lookahead_classes = ClassDefinition::parse(s.read_at_offset16(data)?)?;
+                let count = s.read::<u16>()?;
+                let offsets = s.read_array16(count)?;
+                Some(Self::Format2 {
+                    coverage,
+                    backtrack_classes,
+                    input_classes,
+                    lookahead_classes,
+                    sets: LazyOffsetArray16::new(data, offsets),
+                })
+            }
+            3 => {
+                let backtrack_count = s.read::<u16>()?;
+                let backtrack_coverages = s.read_array16(backtrack_count)?;
+                let input_count = s.read::<u16>()?;
+                let coverage = Coverage::parse(s.read_at_offset16(data)?)?;
+                let input_coverages = s.read_array16(input_count.checked_sub(1)?)?;
+                let lookahead_count = s.read::<u16>()?;
+                let lookahead_coverages = s.read_array16(lookahead_count)?;
+                let lookup_count = s.read::<u16>()?;
+                let lookups = s.read_array16(lookup_count)?;
+                Some(Self::Format3 {
+                    coverage,
+                    backtrack_coverages: LazyOffsetArray16::new(data, backtrack_coverages),
+                    input_coverages: LazyOffsetArray16::new(data, input_coverages),
+                    lookahead_coverages: LazyOffsetArray16::new(data, lookahead_coverages),
+                    lookups,
+                })
+            }
+            _ => None,
+        }
+    }
+
+    /// Returns the subtable coverage.
+    #[inline]
+    pub fn coverage(&self) -> Coverage<'a> {
+        match self {
+            Self::Format1 { coverage, .. } => *coverage,
+            Self::Format2 { coverage, .. } => *coverage,
+            Self::Format3 { coverage, .. } => *coverage,
+        }
+    }
+}
+
+/// A list of [`ChainedSequenceRule`] sets.
+pub type ChainedSequenceRuleSets<'a> = LazyOffsetArray16<'a, ChainedSequenceRuleSet<'a>>;
+
+/// A set of [`ChainedSequenceRule`].
+pub type ChainedSequenceRuleSet<'a> = LazyOffsetArray16<'a, ChainedSequenceRule<'a>>;
+
+impl<'a> FromSlice<'a> for ChainedSequenceRuleSet<'a> {
+    fn parse(data: &'a [u8]) -> Option<Self> {
+        Self::parse(data)
+    }
+}
+
+/// A [Chained Sequence Rule](https://docs.microsoft.com/en-us/typography/opentype/spec/chapter2#chained-sequence-context-format-1-simple-glyph-contexts).
+#[allow(missing_docs)]
+#[derive(Clone, Copy, Debug)]
+pub struct ChainedSequenceRule<'a> {
+    /// Contains either glyph IDs or glyph Classes.
+    pub backtrack: LazyArray16<'a, u16>,
+    pub input: LazyArray16<'a, u16>,
+    /// Contains either glyph IDs or glyph Classes.
+    pub lookahead: LazyArray16<'a, u16>,
+    pub lookups: LazyArray16<'a, SequenceLookupRecord>,
+}
+
+impl<'a> FromSlice<'a> for ChainedSequenceRule<'a> {
+    fn parse(data: &'a [u8]) -> Option<Self> {
+        let mut s = Stream::new(data);
+        let backtrack_count = s.read::<u16>()?;
+        let backtrack = s.read_array16(backtrack_count)?;
+        let input_count = s.read::<u16>()?;
+        let input = s.read_array16(input_count.checked_sub(1)?)?;
+        let lookahead_count = s.read::<u16>()?;
+        let lookahead = s.read_array16(lookahead_count)?;
+        let lookup_count = s.read::<u16>()?;
+        let lookups = s.read_array16(lookup_count)?;
+        Some(Self {
+            backtrack,
+            input,
+            lookahead,
+            lookups,
+        })
+    }
+}

third-party/vendor/ttf-parser/src/ggg/context.rs

@@ -0,0 +1,129 @@
+use super::{ClassDefinition, Coverage, LookupIndex};
+use crate::parser::{FromData, FromSlice, LazyArray16, LazyOffsetArray16, Stream};
+
+/// A [Contextual Lookup Subtable](
+/// https://docs.microsoft.com/en-us/typography/opentype/spec/chapter2#seqctxt1).
+#[allow(missing_docs)]
+#[derive(Clone, Copy, Debug)]
+pub enum ContextLookup<'a> {
+    /// Simple glyph contexts.
+    Format1 {
+        coverage: Coverage<'a>,
+        sets: SequenceRuleSets<'a>,
+    },
+    /// Class-based glyph contexts.
+    Format2 {
+        coverage: Coverage<'a>,
+        classes: ClassDefinition<'a>,
+        sets: SequenceRuleSets<'a>,
+    },
+    /// Coverage-based glyph contexts.
+    Format3 {
+        coverage: Coverage<'a>,
+        coverages: LazyOffsetArray16<'a, Coverage<'a>>,
+        lookups: LazyArray16<'a, SequenceLookupRecord>,
+    },
+}
+
+impl<'a> ContextLookup<'a> {
+    pub(crate) fn parse(data: &'a [u8]) -> Option<Self> {
+        let mut s = Stream::new(data);
+        match s.read::<u16>()? {
+            1 => {
+                let coverage = Coverage::parse(s.read_at_offset16(data)?)?;
+                let count = s.read::<u16>()?;
+                let offsets = s.read_array16(count)?;
+                Some(Self::Format1 {
+                    coverage,
+                    sets: SequenceRuleSets::new(data, offsets),
+                })
+            }
+            2 => {
+                let coverage = Coverage::parse(s.read_at_offset16(data)?)?;
+                let classes = ClassDefinition::parse(s.read_at_offset16(data)?)?;
+                let count = s.read::<u16>()?;
+                let offsets = s.read_array16(count)?;
+                Some(Self::Format2 {
+                    coverage,
+                    classes,
+                    sets: SequenceRuleSets::new(data, offsets),
+                })
+            }
+            3 => {
+                let input_count = s.read::<u16>()?;
+                let lookup_count = s.read::<u16>()?;
+                let coverage = Coverage::parse(s.read_at_offset16(data)?)?;
+                let coverages = s.read_array16(input_count.checked_sub(1)?)?;
+                let lookups = s.read_array16(lookup_count)?;
+                Some(Self::Format3 {
+                    coverage,
+                    coverages: LazyOffsetArray16::new(data, coverages),
+                    lookups,
+                })
+            }
+            _ => None,
+        }
+    }
+
+    /// Returns the subtable coverage.
+    #[inline]
+    pub fn coverage(&self) -> Coverage<'a> {
+        match self {
+            Self::Format1 { coverage, .. } => *coverage,
+            Self::Format2 { coverage, .. } => *coverage,
+            Self::Format3 { coverage, .. } => *coverage,
+        }
+    }
+}
+
+/// A list of [`SequenceRuleSet`]s.
+pub type SequenceRuleSets<'a> = LazyOffsetArray16<'a, SequenceRuleSet<'a>>;
+
+impl<'a> FromSlice<'a> for SequenceRuleSet<'a> {
+    fn parse(data: &'a [u8]) -> Option<Self> {
+        Self::parse(data)
+    }
+}
+
+impl<'a> FromSlice<'a> for SequenceRule<'a> {
+    fn parse(data: &'a [u8]) -> Option<Self> {
+        let mut s = Stream::new(data);
+        let input_count = s.read::<u16>()?;
+        let lookup_count = s.read::<u16>()?;
+        let input = s.read_array16(input_count.checked_sub(1)?)?;
+        let lookups = s.read_array16(lookup_count)?;
+        Some(Self { input, lookups })
+    }
+}
+
+/// A set of [`SequenceRule`]s.
+pub type SequenceRuleSet<'a> = LazyOffsetArray16<'a, SequenceRule<'a>>;
+
+/// A sequence rule.
+#[allow(missing_docs)]
+#[derive(Clone, Copy, Debug)]
+pub struct SequenceRule<'a> {
+    pub input: LazyArray16<'a, u16>,
+    pub lookups: LazyArray16<'a, SequenceLookupRecord>,
+}
+
+/// A sequence rule record.
+#[allow(missing_docs)]
+#[derive(Clone, Copy, Debug)]
+pub struct SequenceLookupRecord {
+    pub sequence_index: u16,
+    pub lookup_list_index: LookupIndex,
+}
+
+impl FromData for SequenceLookupRecord {
+    const SIZE: usize = 4;
+
+    #[inline]
+    fn parse(data: &[u8]) -> Option<Self> {
+        let mut s = Stream::new(data);
+        Some(Self {
+            sequence_index: s.read::<u16>()?,
+            lookup_list_index: s.read::<LookupIndex>()?,
+        })
+    }
+}

third-party/vendor/ttf-parser/src/ggg/feature_variations.rs

@@ -0,0 +1,186 @@
+use super::{Feature, FeatureIndex, RecordListItem, VariationIndex};
+use crate::parser::{FromData, LazyArray16, LazyArray32};
+use crate::parser::{Offset, Offset32, Stream};
+use crate::{NormalizedCoordinate, Tag};
+
+/// A [Feature Variations Table](https://docs.microsoft.com/en-us/typography/opentype/spec/chapter2#featurevariations-table).
+#[derive(Clone, Copy, Debug)]
+pub struct FeatureVariations<'a> {
+    data: &'a [u8],
+    records: LazyArray32<'a, FeatureVariationRecord>,
+}
+
+impl<'a> FeatureVariations<'a> {
+    pub(crate) fn parse(data: &'a [u8]) -> Option<Self> {
+        let mut s = Stream::new(data);
+        let major_version = s.read::<u16>()?;
+        s.skip::<u16>(); // minor version
+        if major_version != 1 {
+            return None;
+        }
+
+        let count = s.read::<u32>()?;
+        let records = s.read_array32(count)?;
+        Some(Self { data, records })
+    }
+
+    /// Returns a [`VariationIndex`] for variation coordinates.
+    pub fn find_index(&self, coords: &[NormalizedCoordinate]) -> Option<VariationIndex> {
+        for i in 0..self.records.len() {
+            let record = self.records.get(i)?;
+            let offset = record.conditions.to_usize();
+            let set = ConditionSet::parse(self.data.get(offset..)?)?;
+            if set.evaluate(coords) {
+                return Some(i);
+            }
+        }
+        None
+    }
+
+    /// Returns a [`Feature`] at specified indices.
+    pub fn find_substitute(
+        &self,
+        feature_index: FeatureIndex,
+        variation_index: VariationIndex,
+    ) -> Option<Feature<'a>> {
+        let offset = self.records.get(variation_index)?.substitutions.to_usize();
+        let subst = FeatureTableSubstitution::parse(self.data.get(offset..)?)?;
+        subst.find_substitute(feature_index)
+    }
+}
+
+#[derive(Clone, Copy, Debug)]
+struct FeatureVariationRecord {
+    conditions: Offset32,
+    substitutions: Offset32,
+}
+
+impl FromData for FeatureVariationRecord {
+    const SIZE: usize = 8;
+
+    #[inline]
+    fn parse(data: &[u8]) -> Option<Self> {
+        let mut s = Stream::new(data);
+        Some(Self {
+            conditions: s.read::<Offset32>()?,
+            substitutions: s.read::<Offset32>()?,
+        })
+    }
+}
+
+#[derive(Clone, Copy, Debug)]
+struct ConditionSet<'a> {
+    data: &'a [u8],
+    conditions: LazyArray16<'a, Offset32>,
+}
+
+impl<'a> ConditionSet<'a> {
+    fn parse(data: &'a [u8]) -> Option<Self> {
+        let mut s = Stream::new(data);
+        let count = s.read::<u16>()?;
+        let conditions = s.read_array16(count)?;
+        Some(Self { data, conditions })
+    }
+
+    fn evaluate(&self, coords: &[NormalizedCoordinate]) -> bool {
+        self.conditions.into_iter().all(|offset| {
+            self.data
+                .get(offset.to_usize()..)
+                .and_then(Condition::parse)
+                .map_or(false, |c| c.evaluate(coords))
+        })
+    }
+}
+
+#[derive(Clone, Copy, Debug)]
+enum Condition {
+    Format1 {
+        axis_index: u16,
+        filter_range_min: i16,
+        filter_range_max: i16,
+    },
+}
+
+impl Condition {
+    fn parse(data: &[u8]) -> Option<Self> {
+        let mut s = Stream::new(data);
+        let format = s.read::<u16>()?;
+        match format {
+            1 => {
+                let axis_index = s.read::<u16>()?;
+                let filter_range_min = s.read::<i16>()?;
+                let filter_range_max = s.read::<i16>()?;
+                Some(Self::Format1 {
+                    axis_index,
+                    filter_range_min,
+                    filter_range_max,
+                })
+            }
+            _ => None,
+        }
+    }
+
+    fn evaluate(&self, coords: &[NormalizedCoordinate]) -> bool {
+        let Self::Format1 {
+            axis_index,
+            filter_range_min,
+            filter_range_max,
+        } = *self;
+        let coord = coords
+            .get(usize::from(axis_index))
+            .map(|c| c.get())
+            .unwrap_or(0);
+        filter_range_min <= coord && coord <= filter_range_max
+    }
+}
+
+#[derive(Clone, Copy, Debug)]
+struct FeatureTableSubstitution<'a> {
+    data: &'a [u8],
+    records: LazyArray16<'a, FeatureTableSubstitutionRecord>,
+}
+
+impl<'a> FeatureTableSubstitution<'a> {
+    fn parse(data: &'a [u8]) -> Option<Self> {
+        let mut s = Stream::new(data);
+        let major_version = s.read::<u16>()?;
+        s.skip::<u16>(); // minor version
+        if major_version != 1 {
+            return None;
+        }
+
+        let count = s.read::<u16>()?;
+        let records = s.read_array16(count)?;
+        Some(Self { data, records })
+    }
+
+    fn find_substitute(&self, feature_index: FeatureIndex) -> Option<Feature<'a>> {
+        for record in self.records {
+            if record.feature_index == feature_index {
+                let offset = record.feature.to_usize();
+                // TODO: set tag
+                return Feature::parse(Tag::from_bytes(b"DFLT"), self.data.get(offset..)?);
+            }
+        }
+        None
+    }
+}
+
+#[derive(Clone, Copy, Debug)]
+struct FeatureTableSubstitutionRecord {
+    feature_index: FeatureIndex,
+    feature: Offset32,
+}
+
+impl FromData for FeatureTableSubstitutionRecord {
+    const SIZE: usize = 6;
+
+    #[inline]
+    fn parse(data: &[u8]) -> Option<Self> {
+        let mut s = Stream::new(data);
+        Some(Self {
+            feature_index: s.read::<FeatureIndex>()?,
+            feature: s.read::<Offset32>()?,
+        })
+    }
+}

third-party/vendor/ttf-parser/src/ggg/layout_table.rs

@@ -0,0 +1,287 @@
+// Suppresses `minor_version` variable warning.
+#![allow(unused_variables)]
+
+#[cfg(feature = "variable-fonts")]
+use super::FeatureVariations;
+use super::LookupList;
+#[cfg(feature = "variable-fonts")]
+use crate::parser::Offset32;
+use crate::parser::{FromData, LazyArray16, Offset, Offset16, Stream};
+use crate::Tag;
+
+/// A [Layout Table](https://docs.microsoft.com/en-us/typography/opentype/spec/chapter2#table-organization).
+#[derive(Clone, Copy, Debug)]
+pub struct LayoutTable<'a> {
+    /// A list of all supported scripts.
+    pub scripts: ScriptList<'a>,
+    /// A list of all supported features.
+    pub features: FeatureList<'a>,
+    /// A list of all lookups.
+    pub lookups: LookupList<'a>,
+    /// Used to substitute an alternate set of lookup tables
+    /// to use for any given feature under specified conditions.
+    #[cfg(feature = "variable-fonts")]
+    pub variations: Option<FeatureVariations<'a>>,
+}
+
+impl<'a> LayoutTable<'a> {
+    pub(crate) fn parse(data: &'a [u8]) -> Option<Self> {
+        let mut s = Stream::new(data);
+
+        let major_version = s.read::<u16>()?;
+        let minor_version = s.read::<u16>()?;
+        if major_version != 1 {
+            return None;
+        }
+
+        let scripts = ScriptList::parse(s.read_at_offset16(data)?)?;
+        let features = FeatureList::parse(s.read_at_offset16(data)?)?;
+        let lookups = LookupList::parse(s.read_at_offset16(data)?)?;
+
+        #[cfg(feature = "variable-fonts")]
+        {
+            let mut variations_offset = None;
+            if minor_version >= 1 {
+                variations_offset = s.read::<Option<Offset32>>()?;
+            }
+
+            let variations = match variations_offset {
+                Some(offset) => data
+                    .get(offset.to_usize()..)
+                    .and_then(FeatureVariations::parse),
+                None => None,
+            };
+
+            Some(Self {
+                scripts,
+                features,
+                lookups,
+                variations,
+            })
+        }
+
+        #[cfg(not(feature = "variable-fonts"))]
+        {
+            Some(Self {
+                scripts,
+                features,
+                lookups,
+            })
+        }
+    }
+}
+
+/// An index in [`ScriptList`].
+pub type ScriptIndex = u16;
+/// An index in [`LanguageSystemList`].
+pub type LanguageIndex = u16;
+/// An index in [`FeatureList`].
+pub type FeatureIndex = u16;
+/// An index in [`LookupList`].
+pub type LookupIndex = u16;
+/// An index in [`FeatureVariations`].
+pub type VariationIndex = u32;
+
+/// A trait to parse item in [`RecordList`].
+///
+/// Internal use only.
+pub trait RecordListItem<'a>: Sized {
+    /// Parses raw data.
+    fn parse(tag: Tag, data: &'a [u8]) -> Option<Self>;
+}
+
+/// A data storage used by [`ScriptList`], [`LanguageSystemList`] and [`FeatureList`] data types.
+#[derive(Clone, Copy, Debug)]
+pub struct RecordList<'a, T: RecordListItem<'a>> {
+    data: &'a [u8],
+    records: LazyArray16<'a, TagRecord>,
+    data_type: core::marker::PhantomData<T>,
+}
+
+impl<'a, T: RecordListItem<'a>> RecordList<'a, T> {
+    fn parse(data: &'a [u8]) -> Option<Self> {
+        let mut s = Stream::new(data);
+        let count = s.read::<u16>()?;
+        let records = s.read_array16(count)?;
+        Some(Self {
+            data,
+            records,
+            data_type: core::marker::PhantomData,
+        })
+    }
+
+    /// Returns a number of items in the RecordList.
+    pub fn len(&self) -> u16 {
+        self.records.len()
+    }
+
+    /// Checks that RecordList is empty.
+    pub fn is_empty(&self) -> bool {
+        self.records.is_empty()
+    }
+
+    /// Returns RecordList value by index.
+    pub fn get(&self, index: u16) -> Option<T> {
+        let record = self.records.get(index)?;
+        self.data
+            .get(record.offset.to_usize()..)
+            .and_then(|data| T::parse(record.tag, data))
+    }
+
+    /// Returns RecordList value by [`Tag`].
+    pub fn find(&self, tag: Tag) -> Option<T> {
+        let record = self
+            .records
+            .binary_search_by(|record| record.tag.cmp(&tag))
+            .map(|p| p.1)?;
+        self.data
+            .get(record.offset.to_usize()..)
+            .and_then(|data| T::parse(record.tag, data))
+    }
+
+    /// Returns RecordList value index by [`Tag`].
+    pub fn index(&self, tag: Tag) -> Option<u16> {
+        self.records
+            .binary_search_by(|record| record.tag.cmp(&tag))
+            .map(|p| p.0)
+    }
+}
+
+impl<'a, T: RecordListItem<'a>> IntoIterator for RecordList<'a, T> {
+    type Item = T;
+    type IntoIter = RecordListIter<'a, T>;
+
+    #[inline]
+    fn into_iter(self) -> Self::IntoIter {
+        RecordListIter {
+            list: self,
+            index: 0,
+        }
+    }
+}
+
+/// An iterator over [`RecordList`] values.
+#[allow(missing_debug_implementations)]
+pub struct RecordListIter<'a, T: RecordListItem<'a>> {
+    list: RecordList<'a, T>,
+    index: u16,
+}
+
+impl<'a, T: RecordListItem<'a>> Iterator for RecordListIter<'a, T> {
+    type Item = T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.index < self.list.len() {
+            self.index += 1;
+            self.list.get(self.index - 1)
+        } else {
+            None
+        }
+    }
+}
+
+/// A list of [`Script`] records.
+pub type ScriptList<'a> = RecordList<'a, Script<'a>>;
+/// A list of [`LanguageSystem`] records.
+pub type LanguageSystemList<'a> = RecordList<'a, LanguageSystem<'a>>;
+/// A list of [`Feature`] records.
+pub type FeatureList<'a> = RecordList<'a, Feature<'a>>;
+
+#[derive(Clone, Copy, Debug)]
+struct TagRecord {
+    tag: Tag,
+    offset: Offset16,
+}
+
+impl FromData for TagRecord {
+    const SIZE: usize = 6;
+
+    #[inline]
+    fn parse(data: &[u8]) -> Option<Self> {
+        let mut s = Stream::new(data);
+        Some(Self {
+            tag: s.read::<Tag>()?,
+            offset: s.read::<Offset16>()?,
+        })
+    }
+}
+
+/// A [Script Table](https://docs.microsoft.com/en-us/typography/opentype/spec/chapter2#script-table-and-language-system-record).
+#[derive(Clone, Copy, Debug)]
+pub struct Script<'a> {
+    /// Script tag.
+    pub tag: Tag,
+    /// Default language.
+    pub default_language: Option<LanguageSystem<'a>>,
+    /// List of supported languages, excluding the default one. Listed alphabetically.
+    pub languages: LanguageSystemList<'a>,
+}
+
+impl<'a> RecordListItem<'a> for Script<'a> {
+    fn parse(tag: Tag, data: &'a [u8]) -> Option<Self> {
+        let mut s = Stream::new(data);
+        let mut default_language = None;
+        if let Some(offset) = s.read::<Option<Offset16>>()? {
+            default_language =
+                LanguageSystem::parse(Tag::from_bytes(b"dflt"), data.get(offset.to_usize()..)?);
+        }
+        let mut languages = RecordList::parse(s.tail()?)?;
+        // Offsets are relative to this table.
+        languages.data = data;
+        Some(Self {
+            tag,
+            default_language,
+            languages,
+        })
+    }
+}
+
+/// A [Language System Table](https://docs.microsoft.com/en-us/typography/opentype/spec/chapter2#language-system-table).
+#[derive(Clone, Copy, Debug)]
+pub struct LanguageSystem<'a> {
+    /// Language tag.
+    pub tag: Tag,
+    /// Index of a feature required for this language system.
+    pub required_feature: Option<FeatureIndex>,
+    /// Array of indices into the FeatureList, in arbitrary order.
+    pub feature_indices: LazyArray16<'a, FeatureIndex>,
+}
+
+impl<'a> RecordListItem<'a> for LanguageSystem<'a> {
+    fn parse(tag: Tag, data: &'a [u8]) -> Option<Self> {
+        let mut s = Stream::new(data);
+        let _lookup_order = s.read::<Offset16>()?; // Unsupported.
+        let required_feature = match s.read::<FeatureIndex>()? {
+            0xFFFF => None,
+            v => Some(v),
+        };
+        let count = s.read::<u16>()?;
+        let feature_indices = s.read_array16(count)?;
+        Some(Self {
+            tag,
+            required_feature,
+            feature_indices,
+        })
+    }
+}
+
+/// A [Feature](https://docs.microsoft.com/en-us/typography/opentype/spec/chapter2#feature-table).
+#[allow(missing_docs)]
+#[derive(Clone, Copy, Debug)]
+pub struct Feature<'a> {
+    pub tag: Tag,
+    pub lookup_indices: LazyArray16<'a, LookupIndex>,
+}
+
+impl<'a> RecordListItem<'a> for Feature<'a> {
+    fn parse(tag: Tag, data: &'a [u8]) -> Option<Self> {
+        let mut s = Stream::new(data);
+        let _params_offset = s.read::<Offset16>()?; // Unsupported.
+        let count = s.read::<u16>()?;
+        let lookup_indices = s.read_array16(count)?;
+        Some(Self {
+            tag,
+            lookup_indices,
+        })
+    }
+}

third-party/vendor/ttf-parser/src/ggg/lookup.rs

@@ -0,0 +1,165 @@
+use crate::parser::{
+    FromData, FromSlice, LazyArray16, LazyOffsetArray16, Offset, Offset16, Offset32, Stream,
+};
+
+/// A list of [`Lookup`] values.
+pub type LookupList<'a> = LazyOffsetArray16<'a, Lookup<'a>>;
+
+/// A [Lookup Table](https://docs.microsoft.com/en-us/typography/opentype/spec/chapter2#lookup-table).
+#[derive(Clone, Copy, Debug)]
+pub struct Lookup<'a> {
+    /// Lookup qualifiers.
+    pub flags: LookupFlags,
+    /// Available subtables.
+    pub subtables: LookupSubtables<'a>,
+    /// Index into GDEF mark glyph sets structure.
+    pub mark_filtering_set: Option<u16>,
+}
+
+impl<'a> FromSlice<'a> for Lookup<'a> {
+    fn parse(data: &'a [u8]) -> Option<Self> {
+        let mut s = Stream::new(data);
+        let kind = s.read::<u16>()?;
+        let flags = s.read::<LookupFlags>()?;
+        let count = s.read::<u16>()?;
+        let offsets = s.read_array16(count)?;
+
+        let mut mark_filtering_set: Option<u16> = None;
+        if flags.use_mark_filtering_set() {
+            mark_filtering_set = Some(s.read::<u16>()?);
+        }
+
+        Some(Self {
+            flags,
+            subtables: LookupSubtables {
+                kind,
+                data,
+                offsets,
+            },
+            mark_filtering_set,
+        })
+    }
+}
+
+/// A trait for parsing Lookup subtables.
+///
+/// Internal use only.
+pub trait LookupSubtable<'a>: Sized {
+    /// Parses raw data.
+    fn parse(data: &'a [u8], kind: u16) -> Option<Self>;
+}
+
+/// A list of lookup subtables.
+#[derive(Clone, Copy)]
+pub struct LookupSubtables<'a> {
+    kind: u16,
+    data: &'a [u8],
+    offsets: LazyArray16<'a, Offset16>,
+}
+
+impl core::fmt::Debug for LookupSubtables<'_> {
+    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
+        write!(f, "LookupSubtables {{ ... }}")
+    }
+}
+
+impl<'a> LookupSubtables<'a> {
+    /// Returns a number of items in the LookupSubtables.
+    #[inline]
+    pub fn len(&self) -> u16 {
+        self.offsets.len()
+    }
+
+    /// Checks if there are any items.
+    pub fn is_empty(&self) -> bool {
+        self.offsets.is_empty()
+    }
+
+    /// Parses a subtable at index.
+    ///
+    /// Accepts either
+    /// [`PositioningSubtable`](crate::gpos::PositioningSubtable)
+    /// or [`SubstitutionSubtable`](crate::gsub::SubstitutionSubtable).
+    ///
+    /// Technically, we can enforce it at compile time, but it makes code too convoluted.
+    pub fn get<T: LookupSubtable<'a>>(&self, index: u16) -> Option<T> {
+        let offset = self.offsets.get(index)?.to_usize();
+        let data = self.data.get(offset..)?;
+        T::parse(data, self.kind)
+    }
+
+    /// Creates an iterator over subtables.
+    ///
+    /// We cannot use `IntoIterator` here, because we have to use user-provided base type.
+    #[allow(clippy::should_implement_trait)]
+    pub fn into_iter<T: LookupSubtable<'a>>(self) -> LookupSubtablesIter<'a, T> {
+        LookupSubtablesIter {
+            data: self,
+            index: 0,
+            data_type: core::marker::PhantomData,
+        }
+    }
+}
+
+/// An iterator over lookup subtables.
+#[allow(missing_debug_implementations)]
+pub struct LookupSubtablesIter<'a, T: LookupSubtable<'a>> {
+    data: LookupSubtables<'a>,
+    index: u16,
+    data_type: core::marker::PhantomData<T>,
+}
+
+impl<'a, T: LookupSubtable<'a>> Iterator for LookupSubtablesIter<'a, T> {
+    type Item = T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.index < self.data.len() {
+            self.index += 1;
+            self.data.get(self.index - 1)
+        } else {
+            None
+        }
+    }
+}
+
+/// Lookup table flags.
+#[allow(missing_docs)]
+#[derive(Clone, Copy, Debug)]
+pub struct LookupFlags(pub u16);
+
+#[rustfmt::skip]
+#[allow(missing_docs)]
+impl LookupFlags {
+    #[inline] pub fn right_to_left(self) -> bool { self.0 & 0x0001 != 0 }
+    #[inline] pub fn ignore_base_glyphs(self) -> bool { self.0 & 0x0002 != 0 }
+    #[inline] pub fn ignore_ligatures(self) -> bool { self.0 & 0x0004 != 0 }
+    #[inline] pub fn ignore_marks(self) -> bool { self.0 & 0x0008 != 0 }
+    #[inline] pub fn ignore_flags(self) -> bool { self.0 & 0x000E != 0 }
+    #[inline] pub fn use_mark_filtering_set(self) -> bool { self.0 & 0x0010 != 0 }
+    #[inline] pub fn mark_attachment_type(self) -> u8 { (self.0 & 0xFF00) as u8 }
+}
+
+impl FromData for LookupFlags {
+    const SIZE: usize = 2;
+
+    #[inline]
+    fn parse(data: &[u8]) -> Option<Self> {
+        u16::parse(data).map(Self)
+    }
+}
+
+pub(crate) fn parse_extension_lookup<'a, T: 'a>(
+    data: &'a [u8],
+    parse: impl FnOnce(&'a [u8], u16) -> Option<T>,
+) -> Option<T> {
+    let mut s = Stream::new(data);
+    let format = s.read::<u16>()?;
+    match format {
+        1 => {
+            let kind = s.read::<u16>()?;
+            let offset = s.read::<Offset32>()?.to_usize();
+            parse(data.get(offset..)?, kind)
+        }
+        _ => None,
+    }
+}

third-party/vendor/ttf-parser/src/ggg/mod.rs

@@ -0,0 +1,168 @@
+//! Common data types used by GDEF/GPOS/GSUB tables.
+//!
+//! <https://docs.microsoft.com/en-us/typography/opentype/spec/chapter2>
+
+// A heavily modified port of https://github.com/RazrFalcon/rustybuzz implementation
+// originally written by https://github.com/laurmaedje
+
+use crate::parser::{FromData, FromSlice, LazyArray16, Stream};
+use crate::GlyphId;
+
+mod chained_context;
+mod context;
+#[cfg(feature = "variable-fonts")]
+mod feature_variations;
+mod layout_table;
+mod lookup;
+
+pub use chained_context::*;
+pub use context::*;
+#[cfg(feature = "variable-fonts")]
+pub use feature_variations::*;
+pub use layout_table::*;
+pub use lookup::*;
+
+/// A record that describes a range of glyph IDs.
+#[derive(Clone, Copy, Debug)]
+pub struct RangeRecord {
+    /// First glyph ID in the range
+    pub start: GlyphId,
+    /// Last glyph ID in the range
+    pub end: GlyphId,
+    /// Coverage Index of first glyph ID in range.
+    pub value: u16,
+}
+
+impl LazyArray16<'_, RangeRecord> {
+    /// Returns a [`RangeRecord`] for a glyph.
+    pub fn range(&self, glyph: GlyphId) -> Option<RangeRecord> {
+        self.binary_search_by(|record| {
+            if glyph < record.start {
+                core::cmp::Ordering::Greater
+            } else if glyph <= record.end {
+                core::cmp::Ordering::Equal
+            } else {
+                core::cmp::Ordering::Less
+            }
+        })
+        .map(|p| p.1)
+    }
+}
+
+impl FromData for RangeRecord {
+    const SIZE: usize = 6;
+
+    #[inline]
+    fn parse(data: &[u8]) -> Option<Self> {
+        let mut s = Stream::new(data);
+        Some(RangeRecord {
+            start: s.read::<GlyphId>()?,
+            end: s.read::<GlyphId>()?,
+            value: s.read::<u16>()?,
+        })
+    }
+}
+
+/// A [Coverage Table](
+/// https://docs.microsoft.com/en-us/typography/opentype/spec/chapter2#coverage-table).
+#[allow(missing_docs)]
+#[derive(Clone, Copy, Debug)]
+pub enum Coverage<'a> {
+    Format1 {
+        /// Array of glyph IDs. Sorted.
+        glyphs: LazyArray16<'a, GlyphId>,
+    },
+    Format2 {
+        /// Array of glyph ranges. Ordered by `RangeRecord.start`.
+        records: LazyArray16<'a, RangeRecord>,
+    },
+}
+
+impl<'a> FromSlice<'a> for Coverage<'a> {
+    fn parse(data: &'a [u8]) -> Option<Self> {
+        let mut s = Stream::new(data);
+        match s.read::<u16>()? {
+            1 => {
+                let count = s.read::<u16>()?;
+                let glyphs = s.read_array16(count)?;
+                Some(Self::Format1 { glyphs })
+            }
+            2 => {
+                let count = s.read::<u16>()?;
+                let records = s.read_array16(count)?;
+                Some(Self::Format2 { records })
+            }
+            _ => None,
+        }
+    }
+}
+
+impl<'a> Coverage<'a> {
+    /// Checks that glyph is present.
+    pub fn contains(&self, glyph: GlyphId) -> bool {
+        self.get(glyph).is_some()
+    }
+
+    /// Returns the coverage index of the glyph or `None` if it is not covered.
+    pub fn get(&self, glyph: GlyphId) -> Option<u16> {
+        match self {
+            Self::Format1 { glyphs } => glyphs.binary_search(&glyph).map(|p| p.0),
+            Self::Format2 { records } => {
+                let record = records.range(glyph)?;
+                let offset = glyph.0 - record.start.0;
+                record.value.checked_add(offset)
+            }
+        }
+    }
+}
+
+/// A value of [Class Definition Table](
+/// https://docs.microsoft.com/en-us/typography/opentype/spec/chapter2#class-definition-table).
+pub type Class = u16;
+
+/// A [Class Definition Table](
+/// https://docs.microsoft.com/en-us/typography/opentype/spec/chapter2#class-definition-table).
+#[allow(missing_docs)]
+#[derive(Clone, Copy, Debug)]
+pub enum ClassDefinition<'a> {
+    Format1 {
+        start: GlyphId,
+        classes: LazyArray16<'a, Class>,
+    },
+    Format2 {
+        records: LazyArray16<'a, RangeRecord>,
+    },
+}
+
+impl<'a> ClassDefinition<'a> {
+    #[inline]
+    pub(crate) fn parse(data: &'a [u8]) -> Option<Self> {
+        let mut s = Stream::new(data);
+        match s.read::<u16>()? {
+            1 => {
+                let start = s.read::<GlyphId>()?;
+                let count = s.read::<u16>()?;
+                let classes = s.read_array16(count)?;
+                Some(Self::Format1 { start, classes })
+            }
+            2 => {
+                let count = s.read::<u16>()?;
+                let records = s.read_array16(count)?;
+                Some(Self::Format2 { records })
+            }
+            _ => None,
+        }
+    }
+
+    /// Returns the glyph class of the glyph (zero if it is not defined).
+    pub fn get(&self, glyph: GlyphId) -> Class {
+        match self {
+            Self::Format1 { start, classes } => glyph
+                .0
+                .checked_sub(start.0)
+                .and_then(|index| classes.get(index)),
+            Self::Format2 { records } => records.range(glyph).map(|record| record.value),
+        }
+        .unwrap_or(0)
+    }
+}