klippa/src/maxp.rs

//! impl subset() for maxp
use crate::{serialize::Serializer, Plan, Subset, SubsetError, SubsetFlags};
use write_fonts::{
    read::{tables::maxp::Maxp, FontRef, TopLevelTable},
    types::Version16Dot16,
    FontBuilder,
};

// reference: subset() for maxp in harfbuzz
// https://github.com/harfbuzz/harfbuzz/blob/a070f9ebbe88dc71b248af9731dd49ec93f4e6e6/src/hb-ot-maxp-table.hh#L97
impl Subset for Maxp<'_> {
    fn subset(
        &self,
        plan: &Plan,
        _font: &FontRef,
        s: &mut Serializer,
        _builder: &mut FontBuilder,
    ) -> Result<(), SubsetError> {
        let num_glyphs = plan.num_output_glyphs.min(0xFFFF) as u16;
        s.embed_bytes(self.offset_data().as_bytes())
            .map_err(|_| SubsetError::SubsetTableError(Maxp::TAG))?;
        s.copy_assign(self.shape().num_glyphs_byte_range().start, num_glyphs);

        //drop hints
        if self.version() == Version16Dot16::VERSION_1_0
            && plan
                .subset_flags
                .contains(SubsetFlags::SUBSET_FLAGS_NO_HINTING)
        {
            //maxZones
            s.copy_assign_from_bytes(self.shape().max_zones_byte_range().unwrap().start, &[0, 1]);
            //maxTwilightPoints..maxSizeOfInstructions
            s.copy_assign(
                self.shape().max_twilight_points_byte_range().unwrap().start,
                0_u16,
            );
            s.copy_assign(self.shape().max_storage_byte_range().unwrap().start, 0_u16);
            s.copy_assign(
                self.shape().max_function_defs_byte_range().unwrap().start,
                0_u16,
            );
            s.copy_assign(
                self.shape()
                    .max_instruction_defs_byte_range()
                    .unwrap()
                    .start,
                0_u16,
            );
            s.copy_assign(
                self.shape().max_stack_elements_byte_range().unwrap().start,
                0_u16,
            );
            s.copy_assign(
                self.shape()
                    .max_size_of_instructions_byte_range()
                    .unwrap()
                    .start,
                0_u16,
            );
        }
        Ok(())
    }
}