read_fonts/tables/
gpos.rs

1//! the [GPOS] table
2//!
3//! [GPOS]: https://docs.microsoft.com/en-us/typography/opentype/spec/gpos
4
5#[path = "./value_record.rs"]
6mod value_record;
7
8use crate::array::ComputedArray;
9
10/// reexport stuff from layout that we use
11pub use super::layout::{
12    ClassDef, CoverageTable, Device, DeviceOrVariationIndex, FeatureList, FeatureVariations,
13    Lookup, ScriptList,
14};
15use super::layout::{ExtensionLookup, LookupFlag, Subtables};
16pub use value_record::ValueRecord;
17
18#[cfg(test)]
19#[path = "../tests/test_gpos.rs"]
20mod spec_tests;
21
22include!("../../generated/generated_gpos.rs");
23
24/// A typed GPOS [LookupList](super::layout::LookupList) table
25pub type PositionLookupList<'a> = super::layout::LookupList<'a, PositionLookup<'a>>;
26
27/// A GPOS [SequenceContext](super::layout::SequenceContext)
28pub type PositionSequenceContext<'a> = super::layout::SequenceContext<'a>;
29
30/// A GPOS [ChainedSequenceContext](super::layout::ChainedSequenceContext)
31pub type PositionChainContext<'a> = super::layout::ChainedSequenceContext<'a>;
32
33impl<'a> AnchorTable<'a> {
34    /// Attempt to resolve the `Device` or `VariationIndex` table for the
35    /// x_coordinate, if present
36    pub fn x_device(&self) -> Option<Result<DeviceOrVariationIndex<'a>, ReadError>> {
37        match self {
38            AnchorTable::Format3(inner) => inner.x_device(),
39            _ => None,
40        }
41    }
42
43    /// Attempt to resolve the `Device` or `VariationIndex` table for the
44    /// y_coordinate, if present
45    pub fn y_device(&self) -> Option<Result<DeviceOrVariationIndex<'a>, ReadError>> {
46        match self {
47            AnchorTable::Format3(inner) => inner.y_device(),
48            _ => None,
49        }
50    }
51}
52
53impl<'a, T: FontRead<'a>> ExtensionLookup<'a, T> for ExtensionPosFormat1<'a, T> {
54    fn extension(&self) -> Result<T, ReadError> {
55        self.extension()
56    }
57}
58
59type PosSubtables<'a, T> = Subtables<'a, T, ExtensionPosFormat1<'a, T>>;
60
61/// The subtables from a GPOS lookup.
62///
63/// This type is a convenience that removes the need to dig into the
64/// [`PositionLookup`] enum in order to access subtables, and it also abstracts
65/// away the distinction between extension and non-extension lookups.
66pub enum PositionSubtables<'a> {
67    Single(PosSubtables<'a, SinglePos<'a>>),
68    Pair(PosSubtables<'a, PairPos<'a>>),
69    Cursive(PosSubtables<'a, CursivePosFormat1<'a>>),
70    MarkToBase(PosSubtables<'a, MarkBasePosFormat1<'a>>),
71    MarkToLig(PosSubtables<'a, MarkLigPosFormat1<'a>>),
72    MarkToMark(PosSubtables<'a, MarkMarkPosFormat1<'a>>),
73    Contextual(PosSubtables<'a, PositionSequenceContext<'a>>),
74    ChainContextual(PosSubtables<'a, PositionChainContext<'a>>),
75}
76
77impl<'a> PositionLookup<'a> {
78    pub fn lookup_flag(&self) -> LookupFlag {
79        self.of_unit_type().lookup_flag()
80    }
81
82    /// Different enumerations for GSUB and GPOS
83    pub fn lookup_type(&self) -> u16 {
84        self.of_unit_type().lookup_type()
85    }
86
87    pub fn mark_filtering_set(&self) -> Option<u16> {
88        self.of_unit_type().mark_filtering_set()
89    }
90
91    /// Return the subtables for this lookup.
92    ///
93    /// This method handles both extension and non-extension lookups, and saves
94    /// the caller needing to dig into the `PositionLookup` enum itself.
95    pub fn subtables(&self) -> Result<PositionSubtables<'a>, ReadError> {
96        let raw_lookup = self.of_unit_type();
97        let offsets = raw_lookup.subtable_offsets();
98        let data = raw_lookup.offset_data();
99        match raw_lookup.lookup_type() {
100            1 => Ok(PositionSubtables::Single(Subtables::new(offsets, data))),
101            2 => Ok(PositionSubtables::Pair(Subtables::new(offsets, data))),
102            3 => Ok(PositionSubtables::Cursive(Subtables::new(offsets, data))),
103            4 => Ok(PositionSubtables::MarkToBase(Subtables::new(offsets, data))),
104            5 => Ok(PositionSubtables::MarkToLig(Subtables::new(offsets, data))),
105            6 => Ok(PositionSubtables::MarkToMark(Subtables::new(offsets, data))),
106            7 => Ok(PositionSubtables::Contextual(Subtables::new(offsets, data))),
107            8 => Ok(PositionSubtables::ChainContextual(Subtables::new(
108                offsets, data,
109            ))),
110            9 => {
111                let first = offsets.first().ok_or(ReadError::OutOfBounds)?.get();
112                let ext: ExtensionPosFormat1<()> = first.resolve(data)?;
113                match ext.extension_lookup_type() {
114                    1 => Ok(PositionSubtables::Single(Subtables::new_ext(offsets, data))),
115                    2 => Ok(PositionSubtables::Pair(Subtables::new_ext(offsets, data))),
116                    3 => Ok(PositionSubtables::Cursive(Subtables::new_ext(
117                        offsets, data,
118                    ))),
119                    4 => Ok(PositionSubtables::MarkToBase(Subtables::new_ext(
120                        offsets, data,
121                    ))),
122                    5 => Ok(PositionSubtables::MarkToLig(Subtables::new_ext(
123                        offsets, data,
124                    ))),
125                    6 => Ok(PositionSubtables::MarkToMark(Subtables::new_ext(
126                        offsets, data,
127                    ))),
128                    7 => Ok(PositionSubtables::Contextual(Subtables::new_ext(
129                        offsets, data,
130                    ))),
131                    8 => Ok(PositionSubtables::ChainContextual(Subtables::new_ext(
132                        offsets, data,
133                    ))),
134                    other => Err(ReadError::InvalidFormat(other as _)),
135                }
136            }
137            other => Err(ReadError::InvalidFormat(other as _)),
138        }
139    }
140}
read_fonts/tables/gpos.rs

read_fonts/tables/
gpos.rs
