[fea-rs] Add options to skip GPOS or GSUB

This is a fairly quick pass, and if future profiling suggests it is
useful we could be more fine-grained in deciding what code to skip
executing. In particular we still perform the full validation pass,
where we could skip some work there as well.

fea-rs/src/bin/compile.rs

@@ -33,9 +33,10 @@ fn run() -> Result<(), Error> {
     }
 
     let var_info = args.get_var_info().transpose()?;
+    let opts = args.opts();
 
     let mut compiler: Compiler<'_, NopFeatureProvider, MockVariationInfo> =
-        Compiler::new(fea, &glyph_names).with_opts(Opts::new().make_post_table(args.post));
+        Compiler::new(fea, &glyph_names).with_opts(opts);
     if let Some(var_info) = var_info.as_ref() {
         log::info!("compiling with {} mock variation axes", var_info.axes.len());
         for axis in &var_info.axes {
@@ -53,9 +54,8 @@ fn run() -> Result<(), Error> {
     let compiled = compiler.compile()?;
 
     let path = args.out_path();
-    let opts = Opts::new().make_post_table(args.post);
     let raw_font = compiled
-        .to_binary(&glyph_names, opts)
+        .to_binary(&glyph_names)
         .expect("ttf compile failed");
 
     log::info!("writing {} bytes to {}", raw_font.len(), path.display());
@@ -137,6 +137,12 @@ struct Args {
     /// Optionally write a post table to the generated font
     #[arg(short, long)]
     post: bool,
+
+    #[arg(long)]
+    skip_gpos: bool,
+
+    #[arg(long)]
+    skip_gsub: bool,
 }
 
 impl Args {
@@ -184,6 +190,13 @@ impl Args {
         self.glyph_order.as_deref()
     }
 
+    fn opts(&self) -> Opts {
+        Opts::new()
+            .make_post_table(self.post)
+            .compile_gpos(!self.skip_gpos)
+            .compile_gsub(!self.skip_gsub)
+    }
+
     fn out_path(&self) -> &Path {
         self.out_path
             .as_deref()

fea-rs/src/compile/compile_ctx.rs

@@ -193,7 +193,7 @@ impl<'a, F: FeatureProvider, V: VariationInfo> CompilationCtx<'a, F, V> {
             .unwrap_or_default();
         let mut ivs = VariationStoreBuilder::new(axis_count);
 
-        let (mut gsub, mut gpos) = self.lookups.build(&self.features, &mut ivs);
+        let (mut gsub, mut gpos) = self.lookups.build(&self.features, &mut ivs, &self.opts);
         if !ivs.is_empty() {
             self.tables
                 .gdef
@@ -1777,9 +1777,13 @@ impl<'a, F: FeatureProvider, V: VariationInfo> CompilationCtx<'a, F, V> {
         } else if let Some(lookup) = typed::LookupBlock::cast(item) {
             self.resolve_lookup_block(lookup);
         } else if let Some(rule) = typed::GsubStatement::cast(item) {
-            self.add_gsub_statement(rule);
+            if self.opts.compile_gsub {
+                self.add_gsub_statement(rule);
+            }
         } else if let Some(rule) = typed::GposStatement::cast(item) {
-            self.add_gpos_statement(rule)
+            if self.opts.compile_gpos {
+                self.add_gpos_statement(rule)
+            }
         } else if item.kind() == Kind::Semi {
             // continue
         } else {

fea-rs/src/compile/lookups.rs

@@ -30,7 +30,7 @@ use write_fonts::{
 use crate::{
     common::{GlyphId, GlyphOrClass, GlyphSet},
     compile::{lookups::contextual::ChainOrNot, metrics::ValueRecord},
-    Kind,
+    Kind, Opts,
 };
 
 use super::{features::AllFeatures, metrics::Anchor, tables::ClassId, tags};
@@ -646,6 +646,7 @@ impl AllLookups {
         &self,
         features: &AllFeatures,
         var_store: &mut VariationStoreBuilder,
+        opts: &Opts,
     ) -> (Option<write_gsub::Gsub>, Option<write_gpos::Gpos>) {
         let mut gpos_builder = PosSubBuilder::new(self.gpos.clone());
         let mut gsub_builder = PosSubBuilder::new(self.gsub.clone());
@@ -661,17 +662,17 @@ impl AllLookups {
             let (gpos_idxes, gsub_idxes) = feature_lookups.split_base_lookups();
             let mut gpos_feat_id = None;
             let mut gsub_feat_id = None;
-            if !gpos_idxes.is_empty() {
+            if opts.compile_gpos && !gpos_idxes.is_empty() {
                 gpos_feat_id = Some(gpos_builder.add(*key, gpos_idxes.clone(), required));
             }
 
-            if !gsub_idxes.is_empty() {
+            if opts.compile_gsub && !gsub_idxes.is_empty() {
                 gsub_feat_id = Some(gsub_builder.add(*key, gsub_idxes.clone(), required));
             }
 
             let variations = feature_lookups.split_variations();
             for (cond, gpos_var_idxes, gsub_var_idxes) in variations {
-                if !gpos_var_idxes.is_empty() {
+                if opts.compile_gpos && !gpos_var_idxes.is_empty() {
                     // add the lookups for the base feature
                     let mut all_ids = gpos_idxes.clone();
                     all_ids.extend(gpos_var_idxes);
@@ -682,7 +683,7 @@ impl AllLookups {
                         .get_or_insert_with(|| gpos_builder.add(*key, Vec::new(), false));
                     gpos_builder.add_variation(*feat_id, cond, all_ids);
                 }
-                if !gsub_var_idxes.is_empty() {
+                if opts.compile_gsub && !gsub_var_idxes.is_empty() {
                     // add the lookups for the base feature
                     let mut all_ids = gsub_idxes.clone();
                     all_ids.extend(gsub_var_idxes);

fea-rs/src/compile/opts.rs

@@ -62,3 +62,46 @@ impl Default for Opts {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+
+    static OSWALD_DIR: &str = "./test-data/real-files/oswald";
+    use std::path::Path;
+
+    use crate::{
+        compile::{Compilation, MockVariationInfo, NopFeatureProvider},
+        Compiler,
+    };
+
+    use super::*;
+
+    #[test]
+    fn skip_tables() {
+        fn compile_oswald(opts: Opts) -> Compilation {
+            let glyph_order = Path::new(OSWALD_DIR).join("glyph_order.txt");
+            let features = Path::new(OSWALD_DIR).join("features.fea");
+            let glyph_order = std::fs::read_to_string(glyph_order).unwrap();
+            let glyph_order = crate::compile::parse_glyph_order(&glyph_order).unwrap();
+            Compiler::<NopFeatureProvider, MockVariationInfo>::new(&features, &glyph_order)
+                .with_opts(opts)
+                .compile()
+                .unwrap()
+        }
+
+        // compile everything:
+        let compilation = compile_oswald(Opts::new());
+        assert!(compilation.gpos.is_some());
+        assert!(compilation.gsub.is_some());
+
+        // only gpos
+        let compilation = compile_oswald(Opts::new().compile_gsub(false));
+        assert!(compilation.gpos.is_some());
+        assert!(compilation.gsub.is_none());
+
+        // only gsub
+        let compilation = compile_oswald(Opts::new().compile_gpos(false));
+        assert!(compilation.gpos.is_none());
+        assert!(compilation.gsub.is_some());
+    }
+}

fea-rs/test-data/real-files/oswald/README.md

@@ -0,0 +1 @@
+This file includes GPOS features generated by fontmake feature writers.