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(glyph: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}
68