1 | //! OpenType layout. |
2 | |
3 | use core::ops::{Index, IndexMut}; |
4 | |
5 | use ttf_parser::opentype_layout::{FeatureIndex, LanguageIndex, LookupIndex, ScriptIndex}; |
6 | use ttf_parser::GlyphId; |
7 | |
8 | use super::apply::{Apply, ApplyContext}; |
9 | use crate::buffer::Buffer; |
10 | use crate::common::TagExt; |
11 | use crate::plan::ShapePlan; |
12 | use crate::{Face, Tag}; |
13 | |
14 | pub const MAX_NESTING_LEVEL: usize = 6; |
15 | pub const MAX_CONTEXT_LENGTH: usize = 64; |
16 | |
17 | #[derive (Clone, Copy, Debug, PartialEq, Eq)] |
18 | pub enum TableIndex { |
19 | GSUB = 0, |
20 | GPOS = 1, |
21 | } |
22 | |
23 | impl TableIndex { |
24 | pub fn iter() -> impl Iterator<Item = TableIndex> { |
25 | [Self::GSUB, Self::GPOS].iter().copied() |
26 | } |
27 | } |
28 | |
29 | impl<T> Index<TableIndex> for [T] { |
30 | type Output = T; |
31 | |
32 | fn index(&self, table_index: TableIndex) -> &Self::Output { |
33 | &self[table_index as usize] |
34 | } |
35 | } |
36 | |
37 | impl<T> IndexMut<TableIndex> for [T] { |
38 | fn index_mut(&mut self, table_index: TableIndex) -> &mut Self::Output { |
39 | &mut self[table_index as usize] |
40 | } |
41 | } |
42 | |
43 | /// A lookup-based layout table (GSUB or GPOS). |
44 | pub trait LayoutTable { |
45 | /// The index of this table. |
46 | const INDEX: TableIndex; |
47 | |
48 | /// Whether lookups in this table can be applied to the buffer in-place. |
49 | const IN_PLACE: bool; |
50 | |
51 | /// The kind of lookup stored in this table. |
52 | type Lookup: LayoutLookup; |
53 | |
54 | /// Get the lookup at the specified index. |
55 | fn get_lookup(&self, index: LookupIndex) -> Option<&Self::Lookup>; |
56 | } |
57 | |
58 | /// A lookup in a layout table. |
59 | pub trait LayoutLookup: Apply { |
60 | /// The lookup's lookup_props. |
61 | fn props(&self) -> u32; |
62 | |
63 | /// Whether the lookup has to be applied backwards. |
64 | fn is_reverse(&self) -> bool; |
65 | |
66 | /// Whether any subtable of the lookup could apply at a specific glyph. |
67 | fn covers(&self, glyph: GlyphId) -> bool; |
68 | } |
69 | |
70 | pub trait LayoutTableExt { |
71 | fn select_script(&self, script_tags: &[Tag]) -> Option<(bool, ScriptIndex, Tag)>; |
72 | fn select_script_language( |
73 | &self, |
74 | script_index: ScriptIndex, |
75 | lang_tags: &[Tag], |
76 | ) -> Option<LanguageIndex>; |
77 | fn get_required_language_feature( |
78 | &self, |
79 | script_index: ScriptIndex, |
80 | lang_index: Option<LanguageIndex>, |
81 | ) -> Option<(FeatureIndex, Tag)>; |
82 | fn find_language_feature( |
83 | &self, |
84 | script_index: ScriptIndex, |
85 | lang_index: Option<LanguageIndex>, |
86 | feature_tag: Tag, |
87 | ) -> Option<FeatureIndex>; |
88 | } |
89 | |
90 | impl LayoutTableExt for ttf_parser::opentype_layout::LayoutTable<'_> { |
91 | /// Returns true + index and tag of the first found script tag in the given GSUB or GPOS table |
92 | /// or false + index and tag if falling back to a default script. |
93 | fn select_script(&self, script_tags: &[Tag]) -> Option<(bool, ScriptIndex, Tag)> { |
94 | for &tag in script_tags { |
95 | if let Some(index) = self.scripts.index(tag) { |
96 | return Some((true, index, tag)); |
97 | } |
98 | } |
99 | |
100 | for &tag in &[ |
101 | // try finding 'DFLT' |
102 | Tag::default_script(), |
103 | // try with 'dflt'; MS site has had typos and many fonts use it now :( |
104 | Tag::default_language(), |
105 | // try with 'latn'; some old fonts put their features there even though |
106 | // they're really trying to support Thai, for example :( |
107 | Tag::from_bytes(b"latn" ), |
108 | ] { |
109 | if let Some(index) = self.scripts.index(tag) { |
110 | return Some((false, index, tag)); |
111 | } |
112 | } |
113 | |
114 | None |
115 | } |
116 | |
117 | /// Returns the index of the first found language tag in the given GSUB or GPOS table, |
118 | /// underneath the specified script index. |
119 | fn select_script_language( |
120 | &self, |
121 | script_index: ScriptIndex, |
122 | lang_tags: &[Tag], |
123 | ) -> Option<LanguageIndex> { |
124 | let script = self.scripts.get(script_index)?; |
125 | |
126 | for &tag in lang_tags { |
127 | if let Some(index) = script.languages.index(tag) { |
128 | return Some(index); |
129 | } |
130 | } |
131 | |
132 | // try finding 'dflt' |
133 | if let Some(index) = script.languages.index(Tag::default_language()) { |
134 | return Some(index); |
135 | } |
136 | |
137 | None |
138 | } |
139 | |
140 | /// Returns the index and tag of a required feature in the given GSUB or GPOS table, |
141 | /// underneath the specified script and language. |
142 | fn get_required_language_feature( |
143 | &self, |
144 | script_index: ScriptIndex, |
145 | lang_index: Option<LanguageIndex>, |
146 | ) -> Option<(FeatureIndex, Tag)> { |
147 | let script = self.scripts.get(script_index)?; |
148 | let sys = match lang_index { |
149 | Some(index) => script.languages.get(index)?, |
150 | None => script.default_language?, |
151 | }; |
152 | let idx = sys.required_feature?; |
153 | let tag = self.features.get(idx)?.tag; |
154 | Some((idx, tag)) |
155 | } |
156 | |
157 | /// Returns the index of a given feature tag in the given GSUB or GPOS table, |
158 | /// underneath the specified script and language. |
159 | fn find_language_feature( |
160 | &self, |
161 | script_index: ScriptIndex, |
162 | lang_index: Option<LanguageIndex>, |
163 | feature_tag: Tag, |
164 | ) -> Option<FeatureIndex> { |
165 | let script = self.scripts.get(script_index)?; |
166 | let sys = match lang_index { |
167 | Some(index) => script.languages.get(index)?, |
168 | None => script.default_language?, |
169 | }; |
170 | |
171 | for i in 0..sys.feature_indices.len() { |
172 | if let Some(index) = sys.feature_indices.get(i) { |
173 | if self.features.get(index).map(|v| v.tag) == Some(feature_tag) { |
174 | return Some(index); |
175 | } |
176 | } |
177 | } |
178 | |
179 | None |
180 | } |
181 | } |
182 | |
183 | /// Applies the lookups in the given GSUB or GPOS table. |
184 | pub fn apply_layout_table<T: LayoutTable>( |
185 | plan: &ShapePlan, |
186 | face: &Face, |
187 | buffer: &mut Buffer, |
188 | table: Option<&T>, |
189 | ) { |
190 | let mut ctx: ApplyContext<'_, '_> = ApplyContext::new(T::INDEX, face, buffer); |
191 | |
192 | for (stage_index: usize, stage: &StageMap) in plan.ot_map.stages(T::INDEX).iter().enumerate() { |
193 | for lookup: &LookupMap in plan.ot_map.stage_lookups(T::INDEX, stage_index) { |
194 | ctx.lookup_index = lookup.index; |
195 | ctx.lookup_mask = lookup.mask; |
196 | ctx.auto_zwj = lookup.auto_zwj; |
197 | ctx.auto_zwnj = lookup.auto_zwnj; |
198 | |
199 | ctx.random = lookup.random; |
200 | |
201 | if let Some(table: &&T) = &table { |
202 | if let Some(lookup: &::Lookup) = table.get_lookup(lookup.index) { |
203 | apply_string::<T>(&mut ctx, lookup); |
204 | } |
205 | } |
206 | } |
207 | |
208 | if let Some(func: fn(&ShapePlan, &Face<'_>, …)) = stage.pause_func { |
209 | func(plan, face, ctx.buffer); |
210 | } |
211 | } |
212 | } |
213 | |
214 | fn apply_string<T: LayoutTable>(ctx: &mut ApplyContext, lookup: &T::Lookup) { |
215 | if ctx.buffer.is_empty() || ctx.lookup_mask == 0 { |
216 | return; |
217 | } |
218 | |
219 | ctx.lookup_props = lookup.props(); |
220 | |
221 | if !lookup.is_reverse() { |
222 | // in/out forward substitution/positioning |
223 | if !T::IN_PLACE { |
224 | ctx.buffer.clear_output(); |
225 | } |
226 | ctx.buffer.idx = 0; |
227 | apply_forward(ctx, lookup); |
228 | |
229 | if !T::IN_PLACE { |
230 | ctx.buffer.sync(); |
231 | } |
232 | } else { |
233 | // in-place backward substitution/positioning |
234 | assert!(!ctx.buffer.have_output); |
235 | |
236 | ctx.buffer.idx = ctx.buffer.len - 1; |
237 | apply_backward(ctx, lookup); |
238 | } |
239 | } |
240 | |
241 | fn apply_forward(ctx: &mut ApplyContext, lookup: &impl Apply) -> bool { |
242 | let mut ret: bool = false; |
243 | while ctx.buffer.idx < ctx.buffer.len && ctx.buffer.successful { |
244 | let cur: &GlyphInfo = ctx.buffer.cur(0); |
245 | if (cur.mask & ctx.lookup_mask) != 0 |
246 | && ctx.check_glyph_property(info:cur, match_props:ctx.lookup_props) |
247 | && lookup.apply(ctx).is_some() |
248 | { |
249 | ret = true; |
250 | } else { |
251 | ctx.buffer.next_glyph(); |
252 | } |
253 | } |
254 | ret |
255 | } |
256 | |
257 | fn apply_backward(ctx: &mut ApplyContext, lookup: &impl Apply) -> bool { |
258 | let mut ret: bool = false; |
259 | loop { |
260 | let cur: &GlyphInfo = ctx.buffer.cur(0); |
261 | ret |= (cur.mask & ctx.lookup_mask) != 0 |
262 | && ctx.check_glyph_property(info:cur, match_props:ctx.lookup_props) |
263 | && lookup.apply(ctx).is_some(); |
264 | |
265 | if ctx.buffer.idx == 0 { |
266 | break; |
267 | } |
268 | |
269 | ctx.buffer.idx -= 1; |
270 | } |
271 | ret |
272 | } |
273 | |
274 | pub fn clear_substitution_flags(_: &ShapePlan, _: &Face, buffer: &mut Buffer) { |
275 | let len: usize = buffer.len; |
276 | for info: &mut GlyphInfo in &mut buffer.info[..len] { |
277 | info.clear_substituted(); |
278 | } |
279 | } |
280 | |
281 | pub fn clear_syllables(_: &ShapePlan, _: &Face, buffer: &mut Buffer) { |
282 | let len: usize = buffer.len; |
283 | for info: &mut GlyphInfo in &mut buffer.info[..len] { |
284 | info.set_syllable(0); |
285 | } |
286 | } |
287 | |