rustybuzz/hb/ot/layout/GSUB/
sequence.rs

1use crate::hb::buffer::GlyphPropsFlags;
2use crate::hb::ot_layout::{
3    _hb_glyph_info_get_lig_id, _hb_glyph_info_is_ligature,
4    _hb_glyph_info_set_lig_props_for_component,
5};
6use crate::hb::ot_layout_gsubgpos::Apply;
7use crate::hb::ot_layout_gsubgpos::OT::hb_ot_apply_context_t;
8use ttf_parser::gsub::Sequence;
9
10impl Apply for Sequence<'_> {
11    fn apply(&self, ctx: &mut hb_ot_apply_context_t) -> Option<()> {
12        match self.substitutes.len() {
13            // Spec disallows this, but Uniscribe allows it.
14            // https://github.com/harfbuzz/harfbuzz/issues/253
15            0 => ctx.buffer.delete_glyph(),
16
17            // Special-case to make it in-place and not consider this
18            // as a "multiplied" substitution.
19            1 => ctx.replace_glyph(self.substitutes.get(0)?),
20
21            _ => {
22                let class = if _hb_glyph_info_is_ligature(ctx.buffer.cur(0)) {
23                    GlyphPropsFlags::BASE_GLYPH
24                } else {
25                    GlyphPropsFlags::empty()
26                };
27                let lig_id = _hb_glyph_info_get_lig_id(ctx.buffer.cur(0));
28
29                for (i, subst) in self.substitutes.into_iter().enumerate() {
30                    // If is attached to a ligature, don't disturb that.
31                    // https://github.com/harfbuzz/harfbuzz/issues/3069
32                    if lig_id == 0 {
33                        // Index is truncated to 4 bits anway, so we can safely cast to u8.
34                        _hb_glyph_info_set_lig_props_for_component(ctx.buffer.cur_mut(0), i as u8);
35                    }
36                    ctx.output_glyph_for_component(subst, class);
37                }
38
39                ctx.buffer.skip_glyph();
40            }
41        }
42        Some(())
43    }
44}