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

1use crate::hb::ot_layout::MAX_NESTING_LEVEL;
2use crate::hb::ot_layout_gsubgpos::OT::hb_ot_apply_context_t;
3use crate::hb::ot_layout_gsubgpos::{
4    match_backtrack, match_lookahead, Apply, WouldApply, WouldApplyContext,
5};
6use ttf_parser::gsub::ReverseChainSingleSubstitution;
7
8// ReverseChainSingleSubstFormat1::would_apply
9impl WouldApply for ReverseChainSingleSubstitution<'_> {
10    fn would_apply(&self, ctx: &WouldApplyContext) -> bool {
11        ctx.glyphs.len() == 1 && self.coverage.get(ctx.glyphs[0]).is_some()
12    }
13}
14
15// ReverseChainSingleSubstFormat1::apply
16impl Apply for ReverseChainSingleSubstitution<'_> {
17    fn apply(&self, ctx: &mut hb_ot_apply_context_t) -> Option<()> {
18        let glyph = ctx.buffer.cur(0).as_glyph();
19        let index = self.coverage.get(glyph)?;
20        if index >= self.substitutes.len() {
21            return None;
22        }
23
24        // No chaining to this type.
25        if ctx.nesting_level_left != MAX_NESTING_LEVEL {
26            return None;
27        }
28
29        let subst = self.substitutes.get(index)?;
30
31        let f1 = |glyph, index| {
32            let value = self.backtrack_coverages.get(index).unwrap();
33            value.contains(glyph)
34        };
35
36        let f2 = |glyph, index| {
37            let value = self.lookahead_coverages.get(index).unwrap();
38            value.contains(glyph)
39        };
40
41        let mut start_index = 0;
42        let mut end_index = 0;
43
44        if match_backtrack(ctx, self.backtrack_coverages.len(), &f1, &mut start_index) {
45            if match_lookahead(
46                ctx,
47                self.lookahead_coverages.len(),
48                &f2,
49                ctx.buffer.idx + 1,
50                &mut end_index,
51            ) {
52                ctx.buffer
53                    .unsafe_to_break_from_outbuffer(Some(start_index), Some(end_index));
54                ctx.replace_glyph_inplace(subst);
55
56                // Note: We DON'T decrease buffer.idx.  The main loop does it
57                // for us.  This is useful for preventing surprises if someone
58                // calls us through a Context lookup.
59                return Some(());
60            }
61        }
62
63        ctx.buffer
64            .unsafe_to_concat_from_outbuffer(Some(start_index), Some(end_index));
65        None
66    }
67}
rustybuzz/hb/ot/layout/GSUB/reverse_chain_single_subst.rs

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