Use fontations for shape planning

Replaces the ttf-parser code for script, langsys and feature lookup.

GSUB/GPOS is now fully fontations.

Author: dfrg

src/hb/face.rs

@@ -4,13 +4,11 @@ use core_maths::CoreFloat;
 
 use crate::hb::paint_extents::hb_paint_extents_context_t;
 use ttf_parser::gdef::GlyphClass;
-use ttf_parser::opentype_layout::LayoutTable;
 use ttf_parser::{GlyphId, RgbaColor};
 
 use super::buffer::GlyphPropsFlags;
 use super::fonta;
 use super::ot_layout::TableIndex;
-use super::ot_layout_common::{PositioningTable, SubstitutionTable};
 use crate::Variation;
 
 /// A font face handle.
@@ -21,8 +19,6 @@ pub struct hb_font_t<'a> {
     pub(crate) units_per_em: u16,
     pixels_per_em: Option<(u16, u16)>,
     pub(crate) points_per_em: Option<f32>,
-    pub(crate) gsub: Option<SubstitutionTable<'a>>,
-    pub(crate) gpos: Option<PositioningTable<'a>>,
 }
 
 impl<'a> AsRef<ttf_parser::Face<'a>> for hb_font_t<'a> {
@@ -67,28 +63,10 @@ impl<'a> hb_font_t<'a> {
             units_per_em: face.units_per_em(),
             pixels_per_em: None,
             points_per_em: None,
-            gsub: face.tables().gsub.map(SubstitutionTable::new),
-            gpos: face.tables().gpos.map(PositioningTable::new),
             ttfp_face: face,
         })
     }
 
-    /// Creates a new [`Face`] from [`ttf_parser::Face`].
-    ///
-    /// Data will be referenced, not owned.
-    pub fn from_face(face: ttf_parser::Face<'a>) -> Self {
-        let font = fonta::Font::new(face.raw_face().data, 0).unwrap();
-        hb_font_t {
-            font,
-            units_per_em: face.units_per_em(),
-            pixels_per_em: None,
-            points_per_em: None,
-            gsub: face.tables().gsub.map(SubstitutionTable::new),
-            gpos: face.tables().gpos.map(PositioningTable::new),
-            ttfp_face: face,
-        }
-    }
-
     // TODO: remove
     /// Returns face’s units per EM.
     #[inline]
@@ -338,17 +316,24 @@ impl<'a> hb_font_t<'a> {
         }
     }
 
-    pub(crate) fn layout_table(&self, table_index: TableIndex) -> Option<&LayoutTable<'a>> {
+    pub(crate) fn layout_table(
+        &self,
+        table_index: TableIndex,
+    ) -> Option<fonta::ot::LayoutTable<'a>> {
         match table_index {
-            TableIndex::GSUB => self.gsub.as_ref().map(|table| &table.inner),
-            TableIndex::GPOS => self.gpos.as_ref().map(|table| &table.inner),
+            TableIndex::GSUB => Some(fonta::ot::LayoutTable::Gsub(
+                self.font.ot.gsub.as_ref()?.table.clone(),
+            )),
+            TableIndex::GPOS => Some(fonta::ot::LayoutTable::Gpos(
+                self.font.ot.gpos.as_ref()?.table.clone(),
+            )),
         }
     }
 
     pub(crate) fn layout_tables(
         &self,
-    ) -> impl Iterator<Item = (TableIndex, &LayoutTable<'a>)> + '_ {
-        TableIndex::iter().filter_map(move |idx| self.layout_table(idx).map(|table| (idx, table)))
+    ) -> impl Iterator<Item = (TableIndex, fonta::ot::LayoutTable<'a>)> + '_ {
+        TableIndex::iter().filter_map(move |idx| Some((idx, self.layout_table(idx)?)))
     }
 }
 

src/hb/fonta/font.rs

@@ -54,14 +54,12 @@ impl<'a> Font<'a> {
     pub(crate) fn set_coords(&mut self, coords: &[NormalizedCoordinate]) {
         self.coords.clear();
         if !coords.is_empty() && !coords.iter().all(|coord| coord.get() == 0) {
+            self.coords.extend(
+                coords
+                    .iter()
+                    .map(|coord| NormalizedCoord::from_bits(coord.get())),
+            );            
             let ivs = self.ivs.take().or_else(|| self.ot.item_variation_store());
-            if ivs.is_some() {
-                self.coords.extend(
-                    coords
-                        .iter()
-                        .map(|coord| NormalizedCoord::from_bits(coord.get())),
-                );
-            }
             self.ivs = ivs;
         } else {
             self.ivs = None;

src/hb/fonta/ot/mod.rs

@@ -1,15 +1,19 @@
 use crate::hb::{
-    hb_font_t,
+    common::TagExt,
+    hb_font_t, hb_tag_t,
     ot_layout::LayoutLookup,
     ot_layout_gsubgpos::{Apply, WouldApply, WouldApplyContext, OT::hb_ot_apply_context_t},
     set_digest::hb_set_digest_ext,
 };
 use skrifa::raw::{
     tables::{
         gdef::Gdef,
-        layout::{ClassDef, CoverageTable},
+        gpos::Gpos,
+        gsub::{FeatureList, FeatureVariations, Gsub, ScriptList},
+        layout::{ClassDef, Condition, CoverageTable, Feature, LangSys, Script},
         variations::ItemVariationStore,
     },
+    types::{F2Dot14, Scalar},
     ReadError, TableProvider,
 };
 use ttf_parser::GlyphId;
@@ -159,6 +163,259 @@ impl LookupInfo {
     }
 }
 
+pub enum LayoutTable<'a> {
+    Gsub(Gsub<'a>),
+    Gpos(Gpos<'a>),
+}
+
+fn conv_tag(tag: hb_tag_t) -> skrifa::raw::types::Tag {
+    skrifa::raw::types::Tag::from_u32(tag.0)
+}
+
+impl<'a> LayoutTable<'a> {
+    fn script_list(&self) -> Option<ScriptList<'a>> {
+        match self {
+            Self::Gsub(gsub) => gsub.script_list().ok(),
+            Self::Gpos(gpos) => gpos.script_list().ok(),
+        }
+    }
+
+    fn feature_list(&self) -> Option<FeatureList<'a>> {
+        match self {
+            Self::Gsub(gsub) => gsub.feature_list().ok(),
+            Self::Gpos(gpos) => gpos.feature_list().ok(),
+        }
+    }
+
+    fn feature_variations(&self) -> Option<FeatureVariations<'a>> {
+        match self {
+            Self::Gsub(gsub) => gsub.feature_variations(),
+            Self::Gpos(gpos) => gpos.feature_variations(),
+        }
+        .transpose()
+        .ok()
+        .flatten()
+    }
+
+    fn script_index(&self, tag: hb_tag_t) -> Option<u16> {
+        let list = self.script_list()?;
+        let tag = conv_tag(tag);
+        list.script_records()
+            .binary_search_by_key(&tag, |rec| rec.script_tag())
+            .map(|index| index as u16)
+            .ok()
+    }
+
+    fn script(&self, index: u16) -> Option<Script<'a>> {
+        let list = self.script_list()?;
+        let record = list.script_records().get(index as usize)?;
+        record.script(list.offset_data()).ok()
+    }
+
+    fn langsys_index(&self, script_index: u16, tag: hb_tag_t) -> Option<u16> {
+        let script = self.script(script_index)?;
+        let tag = conv_tag(tag);
+        script
+            .lang_sys_records()
+            .binary_search_by_key(&tag, |rec| rec.lang_sys_tag())
+            .map(|index| index as u16)
+            .ok()
+    }
+
+    fn langsys(&self, script_index: u16, langsys_index: Option<u16>) -> Option<LangSys<'a>> {
+        let script = self.script(script_index)?;
+        if let Some(index) = langsys_index {
+            let record = script.lang_sys_records().get(index as usize)?;
+            record.lang_sys(script.offset_data()).ok()
+        } else {
+            script.default_lang_sys().transpose().ok().flatten()
+        }
+    }
+
+    pub(crate) fn feature(&self, index: u16) -> Option<Feature<'a>> {
+        let list = self.feature_list()?;
+        let record = list.feature_records().get(index as usize)?;
+        record.feature(list.offset_data()).ok()
+    }
+
+    fn feature_tag(&self, index: u16) -> Option<hb_tag_t> {
+        let list = self.feature_list()?;
+        let record = list.feature_records().get(index as usize)?;
+        Some(hb_tag_t(u32::from_be_bytes(record.feature_tag().to_raw())))
+    }
+
+    pub(crate) fn feature_variation_index(&self, coords: &[F2Dot14]) -> Option<u32> {
+        let feature_variations = self.feature_variations()?;
+        for (index, rec) in feature_variations
+            .feature_variation_records()
+            .iter()
+            .enumerate()
+        {
+            // If the ConditionSet offset is 0, this is treated as the
+            // universal condition: all contexts are matched.
+            if rec.condition_set_offset().is_null() {
+                return Some(index as u32);
+            }
+            let Some(Ok(condition_set)) = rec.condition_set(feature_variations.offset_data())
+            else {
+                continue;
+            };
+            // Otherwise, all conditions must be satisfied.
+            if condition_set
+                .conditions()
+                .iter()
+                // .. except we ignore errors
+                .filter_map(|cond| cond.ok())
+                .all(|cond| match cond {
+                    Condition::Format1AxisRange(format1) => {
+                        let coord = coords
+                            .get(format1.axis_index() as usize)
+                            .copied()
+                            .unwrap_or_default();
+                        coord >= format1.filter_range_min_value()
+                            && coord <= format1.filter_range_max_value()
+                    }
+                    _ => false,
+                })
+            {
+                return Some(index as u32);
+            }
+        }
+        None
+    }
+
+    pub(crate) fn feature_substitution(
+        &self,
+        variation_index: u32,
+        feature_index: u16,
+    ) -> Option<Feature<'a>> {
+        let feature_variations = self.feature_variations()?;
+        let record = feature_variations
+            .feature_variation_records()
+            .get(variation_index as usize)?;
+        let subst_table = record
+            .feature_table_substitution(feature_variations.offset_data())?
+            .ok()?;
+        let subst_records = subst_table.substitutions();
+        match subst_records.binary_search_by_key(&feature_index, |subst| subst.feature_index()) {
+            Ok(ix) => Some(
+                subst_records
+                    .get(ix)?
+                    .alternate_feature(subst_table.offset_data())
+                    .ok()?,
+            ),
+            _ => None,
+        }
+    }
+
+    pub(crate) fn feature_index(&self, tag: hb_tag_t) -> Option<u16> {
+        let list = self.feature_list()?;
+        let tag = conv_tag(tag);
+        for (index, feature) in list.feature_records().iter().enumerate() {
+            if feature.feature_tag() == tag {
+                return Some(index as u16);
+            }
+        }
+        None
+    }
+
+    pub(crate) fn lookup_count(&self) -> u16 {
+        match self {
+            Self::Gsub(gsub) => gsub
+                .lookup_list()
+                .map(|list| list.lookup_count())
+                .unwrap_or_default(),
+            Self::Gpos(gpos) => gpos
+                .lookup_list()
+                .map(|list| list.lookup_count())
+                .unwrap_or_default(),
+        }
+    }
+}
+
+impl crate::hb::ot_layout::LayoutTableExt for LayoutTable<'_> {
+    // hb_ot_layout_table_select_script
+    /// Returns true + index and tag of the first found script tag in the given GSUB or GPOS table
+    /// or false + index and tag if falling back to a default script.
+    fn select_script(&self, script_tags: &[hb_tag_t]) -> Option<(bool, u16, hb_tag_t)> {
+        for &tag in script_tags {
+            if let Some(index) = self.script_index(tag) {
+                return Some((true, index, tag));
+            }
+        }
+
+        for &tag in &[
+            // try finding 'DFLT'
+            hb_tag_t::default_script(),
+            // try with 'dflt'; MS site has had typos and many fonts use it now :(
+            hb_tag_t::default_language(),
+            // try with 'latn'; some old fonts put their features there even though
+            // they're really trying to support Thai, for example :(
+            hb_tag_t::from_bytes(b"latn"),
+        ] {
+            if let Some(index) = self.script_index(tag) {
+                return Some((false, index, tag));
+            }
+        }
+
+        None
+    }
+
+    // hb_ot_layout_script_select_language
+    /// Returns the index of the first found language tag in the given GSUB or GPOS table,
+    /// underneath the specified script index.
+    fn select_script_language(&self, script_index: u16, lang_tags: &[hb_tag_t]) -> Option<u16> {
+        for &tag in lang_tags {
+            if let Some(index) = self.langsys_index(script_index, tag) {
+                return Some(index);
+            }
+        }
+
+        // try finding 'dflt'
+        if let Some(index) = self.langsys_index(script_index, hb_tag_t::default_language()) {
+            return Some(index);
+        }
+
+        None
+    }
+
+    // hb_ot_layout_language_get_required_feature
+    /// Returns the index and tag of a required feature in the given GSUB or GPOS table,
+    /// underneath the specified script and language.
+    fn get_required_language_feature(
+        &self,
+        script_index: u16,
+        lang_index: Option<u16>,
+    ) -> Option<(u16, hb_tag_t)> {
+        let sys = self.langsys(script_index, lang_index)?;
+        let idx = sys.required_feature_index();
+        if idx == 0xFFFF {
+            return None;
+        }
+        let tag = self.feature_tag(idx)?;
+        Some((idx, tag))
+    }
+
+    // hb_ot_layout_language_find_feature
+    /// Returns the index of a given feature tag in the given GSUB or GPOS table,
+    /// underneath the specified script and language.
+    fn find_language_feature(
+        &self,
+        script_index: u16,
+        lang_index: Option<u16>,
+        feature_tag: hb_tag_t,
+    ) -> Option<u16> {
+        let sys = self.langsys(script_index, lang_index)?;
+        for index in sys.feature_indices() {
+            let index = index.get();
+            if self.feature_tag(index) == Some(feature_tag) {
+                return Some(index);
+            }
+        }
+        None
+    }
+}
+
 fn coverage_index(coverage: Result<CoverageTable, ReadError>, gid: GlyphId) -> Option<u16> {
     let gid = skrifa::GlyphId16::new(gid.0);
     coverage.ok().and_then(|coverage| coverage.get(gid))