Merge pull request #716 from googlefonts/nullable-stat-axis-values

[read/write-fonts] make STAT offset_to_axis_values nullable

read-fonts/generated/generated_stat.rs

@@ -121,13 +121,13 @@ impl<'a> Stat<'a> {
     /// start of the design axes value offsets array. If axisValueCount
     /// is zero, set to zero; if axisValueCount is greater than zero,
     /// must be greater than zero.
-    pub fn offset_to_axis_value_offsets(&self) -> Offset32 {
+    pub fn offset_to_axis_value_offsets(&self) -> Nullable<Offset32> {
         let range = self.shape.offset_to_axis_value_offsets_byte_range();
         self.data.read_at(range.start).unwrap()
     }
 
     /// Attempt to resolve [`offset_to_axis_value_offsets`][Self::offset_to_axis_value_offsets].
-    pub fn offset_to_axis_values(&self) -> Result<AxisValueArray<'a>, ReadError> {
+    pub fn offset_to_axis_values(&self) -> Option<Result<AxisValueArray<'a>, ReadError>> {
         let data = self.data;
         let args = self.axis_value_count();
         self.offset_to_axis_value_offsets()

read-fonts/src/tables/stat.rs

@@ -19,7 +19,7 @@ mod tests {
         assert_eq!(axis_record.axis_tag(), Tag::new(b"wght"));
         assert_eq!(axis_record.axis_name_id(), NameId::new(257));
         assert_eq!(axis_record.axis_ordering(), 0);
-        let axis_values = table.offset_to_axis_values().unwrap();
+        let axis_values = table.offset_to_axis_values().unwrap().unwrap();
         let axis_values = axis_values
             .axis_values()
             .iter()

resources/codegen_inputs/stat.rs

@@ -30,8 +30,9 @@ table Stat {
     /// start of the design axes value offsets array. If axisValueCount
     /// is zero, set to zero; if axisValueCount is greater than zero,
     /// must be greater than zero.
+    #[nullable]
     #[read_offset_with($axis_value_count)]
-    #[compile_type(OffsetMarker<Vec<OffsetMarker<AxisValue>>, WIDTH_32>)]
+    #[compile_type(NullableOffsetMarker<Vec<OffsetMarker<AxisValue>>, WIDTH_32>)]
     #[to_owned(convert_axis_value_offsets(obj.offset_to_axis_values()))]
     offset_to_axis_value_offsets: Offset32<AxisValueArray>,
     /// Name ID used as fallback when projection of names into a

write-fonts/generated/generated_stat.rs

@@ -20,7 +20,7 @@ pub struct Stat {
     /// start of the design axes value offsets array. If axisValueCount
     /// is zero, set to zero; if axisValueCount is greater than zero,
     /// must be greater than zero.
-    pub offset_to_axis_values: OffsetMarker<Vec<OffsetMarker<AxisValue>>, WIDTH_32>,
+    pub offset_to_axis_values: NullableOffsetMarker<Vec<OffsetMarker<AxisValue>>, WIDTH_32>,
     /// Name ID used as fallback when projection of names into a
     /// particular font model produces a subfamily name containing only
     /// elidable elements.

write-fonts/src/tables/stat.rs

@@ -11,8 +11,9 @@ impl Stat {
     ) -> Self {
         Stat {
             design_axes: design_axes.into(),
-            offset_to_axis_values: OffsetMarker::new(
-                axis_values.into_iter().map(Into::into).collect(),
+            offset_to_axis_values: NullableOffsetMarker::new(
+                (!axis_values.is_empty())
+                    .then(|| axis_values.into_iter().map(Into::into).collect()),
             ),
             elided_fallback_name_id: Some(elided_fallback_name_id),
         }
@@ -24,12 +25,15 @@ impl Stat {
 // but in write-fonts we want to skip the shim table and just use a vec.
 #[allow(clippy::unwrap_or_default)] // we need to be explicit to provide type info
 fn convert_axis_value_offsets(
-    from: Result<read_fonts::tables::stat::AxisValueArray, ReadError>,
-) -> OffsetMarker<Vec<OffsetMarker<AxisValue>>, WIDTH_32> {
-    from.ok()
-        .map(|array| array.axis_values().to_owned_obj(array.offset_data()))
-        .unwrap_or_else(Vec::new)
-        .into()
+    from: Option<Result<read_fonts::tables::stat::AxisValueArray, ReadError>>,
+) -> NullableOffsetMarker<Vec<OffsetMarker<AxisValue>>, WIDTH_32> {
+    from.map(|inner| {
+        inner
+            .ok()
+            .map(|array| array.axis_values().to_owned_obj(array.offset_data()))
+            .unwrap_or_else(Vec::new)
+    })
+    .into()
 }
 
 #[cfg(test)]
@@ -65,7 +69,7 @@ mod tests {
 
         assert_eq!(read.design_axes().unwrap().len(), 1);
         assert_eq!(read.axis_value_count(), 2);
-        let axis_values = read.offset_to_axis_values().unwrap();
+        let axis_values = read.offset_to_axis_values().unwrap().unwrap();
         assert_eq!(axis_values.axis_value_offsets().len(), 2);
         let value2 = axis_values.axis_values().get(1).unwrap();
         let read_stat::AxisValue::Format1(value2) = value2 else {