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[kerning] Set lookupflags & mark filter set
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This also adds tests that we are generating the expected lookups & flags
for mark & non-mark kerning lookups.
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@cmyr
cmyr committed Mar 14, 2024
1 parent 92997e6 commit 1ea4260
Showing 1 changed file with 155 additions and 42 deletions.
197 changes: 155 additions & 42 deletions fontbe/src/features/kern.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
use std::{
borrow::Cow,
collections::{BTreeMap, BTreeSet, HashMap, HashSet},
sync::Arc,
};

use fea_rs::{
Expand All @@ -19,7 +20,7 @@ use fontdrasil::{
types::GlyphName,
};
use fontir::{
ir::{KernGroup, KernPair, KernParticipant, KerningGroups, KerningInstance},
ir::{Glyph, KernGroup, KernPair, KernParticipant, KerningGroups, KerningInstance},
orchestration::WorkId as FeWorkId,
};
use icu_properties::BidiClass;
Expand Down Expand Up @@ -69,6 +70,13 @@ struct KerningFragmentWork {
#[derive(Debug)]
struct KerningGatherWork;

/// Whether or not a given mark glyph is a spacing mark, e.g. has width
#[derive(Clone, Copy, Debug)]
enum MarkSpacing {
Spacing,
NonSpacing,
}

pub fn create_gather_ir_kerning_work() -> Box<BeWork> {
Box::new(GatherIrKerningWork {})
}
Expand Down Expand Up @@ -401,7 +409,7 @@ impl Work<Context, AnyWorkId, Error> for KerningGatherWork {
)
})
.collect::<Vec<_>>();
let lookups = self.finalize_kerning(&fragments, &ast.ast, &glyph_map, &glyphs_and_gids)?;
let lookups = self.finalize_kerning(&fragments, &ast.ast, &glyph_map, glyphs_and_gids)?;
context.fea_rs_kerns.set(lookups);
Ok(())
}
Expand All @@ -416,7 +424,7 @@ impl KerningGatherWork {
fragments: &[&KernFragment],
ast: &ParseTree,
glyph_map: &GlyphMap,
glyphs: &impl CharMap,
glyphs: Vec<(Arc<Glyph>, GlyphId)>,
) -> Result<FeaRsKerns, Error> {
// ignore diagnostics, they'll get logged during actual GSUB compilation
let (compilation, _) = fea_rs::compile::compile::<NopVariationInfo, NopFeatureProvider>(
Expand Down Expand Up @@ -448,8 +456,29 @@ impl KerningGatherWork {
.flat_map(|frag| frag.kerns.iter())
.collect::<Vec<_>>();

let known_scripts = guess_font_scripts(ast, glyphs);
let split_ctx = KernSplitContext::new(glyphs, &known_scripts, gsub, gdef)?;
let known_scripts = guess_font_scripts(ast, &glyphs);
let mark_glyphs = glyphs
.iter()
.filter_map(|(glyph, gid)| {
let is_mark = gdef
.as_ref()
.map(|gdef| gdef.get(gid) == Some(&GlyphClassDef::Mark))
.unwrap_or(false);
is_mark.then(|| {
let spacing = if glyph
.sources()
.values()
.all(|instance| instance.width != 0.0)
{
MarkSpacing::Spacing
} else {
MarkSpacing::NonSpacing
};
(*gid, spacing)
})
})
.collect();
let split_ctx = KernSplitContext::new(&glyphs, &known_scripts, gsub, mark_glyphs)?;

let lookups = split_ctx.make_lookups(&pairs);
let (lookups, features) = self.assign_lookups_to_scripts(lookups, ast, KERN);
Expand Down Expand Up @@ -590,7 +619,8 @@ fn debug_ordered_lookups(

/// All the state needed for splitting kern pairs by script & writing direction
struct KernSplitContext {
gdef: Option<HashMap<GlyphId, GlyphClassDef>>,
/// map of all mark glyphs; bool indicates if mark is spacing
mark_glyphs: HashMap<GlyphId, MarkSpacing>,
glyph_scripts: HashMap<GlyphId, HashSet<UnicodeShortName>>,
bidi_glyphs: HashMap<BidiClass, HashSet<GlyphId>>,
opts: KernSplitOptions,
Expand All @@ -614,14 +644,14 @@ impl KernSplitContext {
glyphs: &impl CharMap,
known_scripts: &HashSet<UnicodeShortName>,
gsub: Option<Gsub>,
gdef: Option<HashMap<GlyphId, GlyphClassDef>>,
mark_glyphs: HashMap<GlyphId, MarkSpacing>,
) -> Result<Self, ReadError> {
let glyph_scripts =
super::properties::scripts_by_glyph(glyphs, known_scripts, gsub.as_ref())?;
let bidi_glyphs = super::properties::glyphs_by_bidi_class(glyphs, gsub.as_ref())?;

Ok(Self {
gdef,
mark_glyphs,
glyph_scripts,
bidi_glyphs,
opts: KernSplitOptions::default(),
Expand All @@ -630,18 +660,6 @@ impl KernSplitContext {
})
}

fn mark_glyph_ids(&self) -> HashSet<GlyphId> {
self.gdef
.as_ref()
.map(|classes| {
classes
.iter()
.filter_map(|(gid, cls)| (*cls == GlyphClassDef::Mark).then_some(*gid))
.collect()
})
.unwrap_or_default()
}

// <https://github.com/googlefonts/ufo2ft/blob/cea60d71dfc/Lib/ufo2ft/featureWriters/kernFeatureWriter.py#L242>
fn make_lookups(
&self,
Expand Down Expand Up @@ -674,8 +692,7 @@ impl KernSplitContext {
fn make_split_script_kern_lookups(
&self,
pairs: &[Cow<PairPosEntry>],
//TODO: handle marks
_are_marks: bool,
are_marks: bool,
) -> BTreeMap<BTreeSet<UnicodeShortName>, Vec<PendingLookup<PairPosBuilder>>> {
let mut lookups_by_script = BTreeMap::new();
let kerning_per_script = self.split_kerns(pairs);
Expand Down Expand Up @@ -710,12 +727,39 @@ impl KernSplitContext {
}
pair.add_to(&mut builder);
}
let lookup = PendingLookup::new(vec![builder], LookupFlag::empty(), None);
let lookup = self.make_lookup(builder, !are_marks);
lookups_by_script.insert(scripts, vec![lookup]);
}
lookups_by_script
}

// logic from
// <https://github.com/googlefonts/ufo2ft/blob/cea60d71dfc/Lib/ufo2ft/featureWriters/kernFeatureWriter.py#L385>
fn make_lookup(
&self,
builder: PairPosBuilder,
ignore_marks: bool,
) -> PendingLookup<PairPosBuilder> {
let mut flags = LookupFlag::empty();
let mut filter_class = None;
if ignore_marks && self.opts.ignore_marks {
let spacing_marks: GlyphSet = self
.mark_glyphs
.iter()
.filter_map(|(gid, spacing)| {
matches!(spacing, MarkSpacing::Spacing).then_some(*gid)
})
.collect();
if spacing_marks.is_empty() {
flags.set_ignore_marks(true);
} else {
filter_class = Some(spacing_marks);
flags.set_use_mark_filtering_set(true);
}
}
PendingLookup::new(vec![builder], flags, filter_class)
}

// <https://github.com/googlefonts/ufo2ft/blob/f6b4f42460b/Lib/ufo2ft/featureWriters/kernFeatureWriter.py#L842>
fn split_kerns(
&self,
Expand Down Expand Up @@ -842,10 +886,10 @@ impl KernSplitContext {
// little helper to tell us what's in a glyphset
fn classify_glyphset_contents(
glyph_set: &GlyphSet,
marks: &HashSet<GlyphId>,
marks: &HashMap<GlyphId, MarkSpacing>,
) -> GlyphSetContent {
glyph_set.iter().fold(GlyphSetContent::Empty, |val, gid| {
match (val, marks.contains(&gid)) {
match (val, marks.contains_key(&gid)) {
(GlyphSetContent::Empty, true) => GlyphSetContent::MarksOnly,
(GlyphSetContent::Empty, false) => GlyphSetContent::BasesOnly,
(GlyphSetContent::MarksOnly, true) => GlyphSetContent::MarksOnly,
Expand All @@ -856,13 +900,15 @@ impl KernSplitContext {
}

/// split a glyphset into (bases, marks)
fn split_glyphs(glyphs: &GlyphSet, marks: &HashSet<GlyphId>) -> (GlyphSet, GlyphSet) {
let (x, y): (Vec<_>, Vec<_>) = glyphs.iter().partition(|gid| !marks.contains(gid));
fn split_glyphs(
glyphs: &GlyphSet,
marks: &HashMap<GlyphId, MarkSpacing>,
) -> (GlyphSet, GlyphSet) {
let (x, y): (Vec<_>, Vec<_>) = glyphs.iter().partition(|gid| !marks.contains_key(gid));
(x.into(), y.into())
}

let marks = self.mark_glyph_ids();
if marks.is_empty() {
if self.mark_glyphs.is_empty() {
return (
pairs.iter().map(|x| Cow::Borrowed(*x)).collect(),
Vec::new(),
Expand All @@ -874,16 +920,17 @@ impl KernSplitContext {
for pair in pairs {
match pair {
PairPosEntry::Pair(side1, _, side2, _)
if !marks.contains(side1) && !marks.contains(side2) =>
if !self.mark_glyphs.contains_key(side1)
&& !self.mark_glyphs.contains_key(side2) =>
{
base_pairs.push(Cow::Borrowed(*pair))
}
PairPosEntry::Pair(..) => mark_pairs.push(Cow::Borrowed(*pair)),

// handle the case where all are marks or bases, first:
PairPosEntry::Class(side1, val1, side2, val2) => {
let side1_cls = classify_glyphset_contents(side1, &marks);
let side2_cls = classify_glyphset_contents(side2, &marks);
let side1_cls = classify_glyphset_contents(side1, &self.mark_glyphs);
let side2_cls = classify_glyphset_contents(side2, &self.mark_glyphs);

match (side1_cls, side2_cls) {
(GlyphSetContent::Empty, _) | (_, GlyphSetContent::Empty) => continue,
Expand All @@ -898,8 +945,8 @@ impl KernSplitContext {
continue;
}
_ => {
let (side1_bases, side1_marks) = split_glyphs(side1, &marks);
let (side2_bases, side2_marks) = split_glyphs(side2, &marks);
let (side1_bases, side1_marks) = split_glyphs(side1, &self.mark_glyphs);
let (side2_bases, side2_marks) = split_glyphs(side2, &self.mark_glyphs);

if !side1_bases.is_empty() && !side2_bases.is_empty() {
base_pairs.push(Cow::Owned(PairPosEntry::Class(
Expand Down Expand Up @@ -1037,6 +1084,7 @@ fn merge_scripts(
mod tests {
use super::*;

const LATN: UnicodeShortName = unsafe { UnicodeShortName::from_bytes_unchecked(*b"Latn") };
struct MockCharMap(HashMap<char, GlyphId>);

impl CharMap for MockCharMap {
Expand All @@ -1047,15 +1095,17 @@ mod tests {

impl MockCharMap {
fn make_rule(&self, left: char, right: char, val: i16) -> PairPosEntry {
let left = self.0.get(&left).unwrap();
let right = self.0.get(&right).unwrap();
PairPosEntry::Pair(
*left,
self.get(left),
ValueRecordBuilder::new().with_x_advance(val),
*right,
self.get(right),
ValueRecordBuilder::new(),
)
}

fn get(&self, c: char) -> GlyphId {
self.0.get(&c).copied().unwrap()
}
}

impl FromIterator<char> for MockCharMap {
Expand All @@ -1079,7 +1129,8 @@ mod tests {
.into_iter()
.map(|(a, b, val)| charmap.make_rule(a, b, val))
.collect::<Vec<_>>();
let ctx = KernSplitContext::new(&charmap, &known_scripts, None, None).unwrap();
let ctx =
KernSplitContext::new(&charmap, &known_scripts, None, Default::default()).unwrap();

let pairs_ref = pairs.iter().collect::<Vec<_>>();

Expand All @@ -1090,9 +1141,7 @@ mod tests {
.into_iter()
.collect();

let latn: BTreeSet<_> = [UnicodeShortName::from_str("Latn").unwrap()]
.into_iter()
.collect();
let latn: BTreeSet<_> = [LATN].into_iter().collect();

let cyr_rules = result.get(&cyrillic).unwrap();
assert_eq!(
Expand All @@ -1112,4 +1161,68 @@ mod tests {
2
);
}

fn flags_and_rule_count(lookup: &PendingLookup<PairPosBuilder>) -> (LookupFlag, usize) {
(
lookup.flags,
lookup.subtables.iter().map(|sub| sub.len()).sum::<usize>(),
)
}

#[test]
fn mark_to_base_kern() {
const ACUTE_COMB: char = '\u{0301}';
let charmap: MockCharMap = ['A', 'B', 'C', ACUTE_COMB].into_iter().collect();
let known_scripts = scripts_for_chars(&charmap);
let mark_glyphs = [(charmap.get(ACUTE_COMB), MarkSpacing::NonSpacing)]
.into_iter()
.collect();
let pairs = [('A', ACUTE_COMB, -55), ('B', 'C', -30), ('A', 'C', -22)]
.into_iter()
.map(|(a, b, val)| charmap.make_rule(a, b, val))
.collect::<Vec<_>>();

let ctx = KernSplitContext::new(&charmap, &known_scripts, None, mark_glyphs).unwrap();

let pairs_ref = pairs.iter().collect::<Vec<_>>();
let result = ctx.make_lookups(&pairs_ref);

let latn: BTreeSet<_> = [LATN].into_iter().collect();
assert_eq!(result.len(), 1);
let lookups = result.get(&latn).unwrap();
assert_eq!(lookups.len(), 2);

let mut ignore_marks = LookupFlag::empty();
ignore_marks.set_ignore_marks(true);

let bases = &lookups[0];
let marks = &lookups[1];
assert_eq!(
(flags_and_rule_count(bases), flags_and_rule_count(marks)),
((ignore_marks, 2), (LookupFlag::empty(), 1)),
);
}

#[test]
fn mark_to_base_only() {
const ACUTE_COMB: char = '\u{0301}';
let charmap: MockCharMap = ['A', 'B', 'C', ACUTE_COMB].into_iter().collect();
let known_scripts = scripts_for_chars(&charmap);
let mark_glyphs = [(charmap.get(ACUTE_COMB), MarkSpacing::NonSpacing)]
.into_iter()
.collect();
let pairs = vec![charmap.make_rule('A', ACUTE_COMB, -55)];

let ctx = KernSplitContext::new(&charmap, &known_scripts, None, mark_glyphs).unwrap();

let pairs_ref = pairs.iter().collect::<Vec<_>>();
let result = ctx.make_lookups(&pairs_ref);

let latn: BTreeSet<_> = [LATN].into_iter().collect();
assert_eq!(result.len(), 1);
let lookups = result.get(&latn).unwrap();
assert_eq!(lookups.len(), 1);

assert_eq!(flags_and_rule_count(&lookups[0]), (LookupFlag::empty(), 1));
}
}

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