Minor fixes

src/cff2.rs

@@ -7,7 +7,7 @@ use std::borrow::Cow;
 pub fn subset(ctx: &mut Context) -> crate::Result<()> {
     let mut maxp_data = MaxpData::default();
 
-    let result = glyf::subset_with(ctx, |old_gid, ctx| {
+    glyf::subset_with(ctx, |old_gid, ctx| {
         let data = match &ctx.interjector {
             // We reject CFF2 fonts earlier if `variable-fonts` feature is not enabled.
             Interjector::Dummy(_) => unreachable!(),
@@ -18,8 +18,8 @@ pub fn subset(ctx: &mut Context) -> crate::Result<()> {
         };
 
         Ok(data)
-    });
+    })?;
 
     ctx.custom_maxp_data = Some(maxp_data);
-    result
+    Ok(())
 }

src/glyf.rs

@@ -47,7 +47,9 @@ pub fn closure(face: &Face, glyph_remapper: &mut GlyphRemapper) -> Result<()> {
 
 pub fn subset(ctx: &mut Context) -> Result<()> {
     let table = Table::new(&ctx.face).ok_or(MalformedFont)?;
-    let mut _maxp = MaxpData::default();
+
+    #[allow(unused_mut)]
+    let mut maxp_data = MaxpData::default();
 
     subset_with(ctx, |old_gid, ctx| {
         let data = match &ctx.interjector {
@@ -56,12 +58,18 @@ pub fn subset(ctx: &mut Context) -> Result<()> {
             }
             #[cfg(feature = "variable-fonts")]
             Interjector::Skrifa(s) => {
-                Cow::Owned(s.glyph_data(&mut _maxp, old_gid).ok_or(MalformedFont)?)
+                Cow::Owned(s.glyph_data(&mut maxp_data, old_gid).ok_or(MalformedFont)?)
             }
         };
 
         Ok(data)
-    })
+    })?;
+
+    if ctx.interjector.is_skrifa() {
+        ctx.custom_maxp_data = Some(maxp_data);
+    }
+
+    Ok(())
 }
 
 pub(crate) fn subset_with<'a>(

src/hmtx.rs

@@ -60,7 +60,7 @@ pub fn subset(ctx: &mut Context) -> Result<()> {
 
     let hhea = ctx.expect_table(Tag::HHEA).ok_or(MalformedFont)?;
     let mut sub_hhea = Writer::new();
-    sub_hhea.extend(&hhea[0..hhea.len() - 2]);
+    sub_hhea.extend(hhea.get(..hhea.len() - 2).ok_or(MalformedFont)?);
     sub_hhea.write::<u16>(last_advance_width_index + 1);
 
     ctx.push(Tag::HHEA, sub_hhea.finish());

src/interjector.rs

@@ -6,6 +6,16 @@ pub(crate) enum Interjector<'a> {
     Skrifa(skrifa::SkrifaInterjector<'a>),
 }
 
+impl Interjector<'_> {
+    pub fn is_skrifa(&self) -> bool {
+        match self {
+            Self::Dummy(_) => false,
+            #[cfg(feature = "variable-fonts")]
+            Self::Skrifa(_) => true,
+        }
+    }
+}
+
 #[cfg(feature = "variable-fonts")]
 pub(crate) mod skrifa {
     use crate::{MaxpData, Tag};

src/lib.rs

@@ -221,9 +221,15 @@ fn _subset(mut ctx: Context) -> Result<Vec<u8>> {
     if ctx.flavor == FontFlavor::TrueType {
         // LOCA will be handled by GLYF
         ctx.process(Tag::GLYF)?;
-        ctx.process(Tag::CVT)?; // won't be subsetted.
-        ctx.process(Tag::FPGM)?; // won't be subsetted.
-        ctx.process(Tag::PREP)?; // won't be subsetted.
+
+        // Only copy hinting tables if we don't interject because skrifa will
+        // discard hinting information.
+        // TODO: Add a test for this.
+        if !ctx.interjector.is_skrifa() {
+            ctx.process(Tag::CVT)?; // won't be subsetted.
+            ctx.process(Tag::FPGM)?; // won't be subsetted.
+            ctx.process(Tag::PREP)?; // won't be subsetted.
+        }
     } else if ctx.flavor == FontFlavor::Cff {
         ctx.process(Tag::CFF)?;
     } else if ctx.flavor == FontFlavor::Cff2 {
@@ -303,7 +309,8 @@ fn construct(mut ctx: Context) -> Vec<u8> {
     let mut offset = 12 + ctx.tables.len() * 16;
     for (tag, data) in &mut ctx.tables {
         if *tag == Tag::HEAD {
-            // Zero out checksum field in head table.
+            // Zero out checksum field in head table. The head table has already
+            // been subset and is guaranteed to have the necessary minimum size.
             data.to_mut()[8..12].fill(0);
             checksum_adjustment_offset = Some(offset + 8);
         }
@@ -551,7 +558,7 @@ impl Tag {
 }
 
 impl Readable<'_> for Tag {
-    const SIZE: usize = u8::SIZE * 4;
+    const SIZE: usize = 4;
 
     fn read(r: &mut Reader) -> Option<Self> {
         r.read::<[u8; 4]>().map(Self)

src/read.rs

@@ -99,7 +99,7 @@ pub trait Readable<'a>: Sized {
 }
 
 impl<const N: usize> Readable<'_> for [u8; N] {
-    const SIZE: usize = u8::SIZE * N;
+    const SIZE: usize = N;
 
     fn read(r: &mut Reader) -> Option<Self> {
         Some(r.read_bytes(N)?.try_into().unwrap_or([0; N]))

tests/ttx/NotoSans-Regular_var_1.ttx

@@ -23,7 +23,7 @@
     <!-- Most of this table will be recalculated by the compiler -->
     <tableVersion value="1.0"/>
     <fontRevision value="2.013"/>
-    <checkSumAdjustment value="0xf8bea5c9"/>
+    <checkSumAdjustment value="0xf902a8a3"/>
     <magicNumber value="0x5f0f3cf5"/>
     <flags value="00000000 00000011"/>
     <unitsPerEm value="1000"/>
@@ -64,18 +64,18 @@
     <!-- Most of this table will be recalculated by the compiler -->
     <tableVersion value="0x10000"/>
     <numGlyphs value="14"/>
-    <maxPoints value="273"/>
-    <maxContours value="24"/>
-    <maxCompositePoints value="143"/>
-    <maxCompositeContours value="8"/>
+    <maxPoints value="51"/>
+    <maxContours value="2"/>
+    <maxCompositePoints value="0"/>
+    <maxCompositeContours value="0"/>
     <maxZones value="1"/>
     <maxTwilightPoints value="0"/>
     <maxStorage value="0"/>
     <maxFunctionDefs value="0"/>
     <maxInstructionDefs value="0"/>
     <maxStackElements value="0"/>
     <maxSizeOfInstructions value="0"/>
-    <maxComponentElements value="4"/>
+    <maxComponentElements value="0"/>
     <maxComponentDepth value="1"/>
   </maxp>
 

tests/ttx/NotoSans-Regular_var_2.ttx

@@ -23,7 +23,7 @@
     <!-- Most of this table will be recalculated by the compiler -->
     <tableVersion value="1.0"/>
     <fontRevision value="2.013"/>
-    <checkSumAdjustment value="0xe1c0756b"/>
+    <checkSumAdjustment value="0xe2047845"/>
     <magicNumber value="0x5f0f3cf5"/>
     <flags value="00000000 00000011"/>
     <unitsPerEm value="1000"/>
@@ -64,18 +64,18 @@
     <!-- Most of this table will be recalculated by the compiler -->
     <tableVersion value="0x10000"/>
     <numGlyphs value="14"/>
-    <maxPoints value="273"/>
-    <maxContours value="24"/>
-    <maxCompositePoints value="143"/>
-    <maxCompositeContours value="8"/>
+    <maxPoints value="51"/>
+    <maxContours value="2"/>
+    <maxCompositePoints value="0"/>
+    <maxCompositeContours value="0"/>
     <maxZones value="1"/>
     <maxTwilightPoints value="0"/>
     <maxStorage value="0"/>
     <maxFunctionDefs value="0"/>
     <maxInstructionDefs value="0"/>
     <maxStackElements value="0"/>
     <maxSizeOfInstructions value="0"/>
-    <maxComponentElements value="4"/>
+    <maxComponentElements value="0"/>
     <maxComponentDepth value="1"/>
   </maxp>
 

tests/ttx/NotoSans-Regular_var_3.ttx

@@ -23,7 +23,7 @@
     <!-- Most of this table will be recalculated by the compiler -->
     <tableVersion value="1.0"/>
     <fontRevision value="2.013"/>
-    <checkSumAdjustment value="0xec15e09b"/>
+    <checkSumAdjustment value="0xec59e375"/>
     <magicNumber value="0x5f0f3cf5"/>
     <flags value="00000000 00000011"/>
     <unitsPerEm value="1000"/>
@@ -64,18 +64,18 @@
     <!-- Most of this table will be recalculated by the compiler -->
     <tableVersion value="0x10000"/>
     <numGlyphs value="14"/>
-    <maxPoints value="273"/>
-    <maxContours value="24"/>
-    <maxCompositePoints value="143"/>
-    <maxCompositeContours value="8"/>
+    <maxPoints value="51"/>
+    <maxContours value="2"/>
+    <maxCompositePoints value="0"/>
+    <maxCompositeContours value="0"/>
     <maxZones value="1"/>
     <maxTwilightPoints value="0"/>
     <maxStorage value="0"/>
     <maxFunctionDefs value="0"/>
     <maxInstructionDefs value="0"/>
     <maxStackElements value="0"/>
     <maxSizeOfInstructions value="0"/>
-    <maxComponentElements value="4"/>
+    <maxComponentElements value="0"/>
     <maxComponentDepth value="1"/>
   </maxp>