1//! A [Vertical Metrics Variations Table](
2//! https://docs.microsoft.com/en-us/typography/opentype/spec/hvar) implementation.
3
4use crate::delta_set::DeltaSetIndexMap;
5use crate::parser::{Offset, Offset32, Stream};
6use crate::var_store::ItemVariationStore;
7use crate::{GlyphId, NormalizedCoordinate};
8
9/// A [Vertical Metrics Variations Table](
10/// https://docs.microsoft.com/en-us/typography/opentype/spec/hvar).
11#[derive(Clone, Copy)]
12pub struct Table<'a> {
13 data: &'a [u8],
14 variation_store: ItemVariationStore<'a>,
15 advance_height_mapping_offset: Option<Offset32>,
16 tsb_mapping_offset: Option<Offset32>,
17 bsb_mapping_offset: Option<Offset32>,
18 vorg_mapping_offset: Option<Offset32>,
19}
20
21impl<'a> Table<'a> {
22 /// Parses a table from raw data.
23 pub fn parse(data: &'a [u8]) -> Option<Self> {
24 let mut s = Stream::new(data);
25
26 let version = s.read::<u32>()?;
27 if version != 0x00010000 {
28 return None;
29 }
30
31 let variation_store_offset = s.read::<Offset32>()?;
32 let var_store_s = Stream::new_at(data, variation_store_offset.to_usize())?;
33 let variation_store = ItemVariationStore::parse(var_store_s)?;
34
35 Some(Table {
36 data,
37 variation_store,
38 advance_height_mapping_offset: s.read::<Option<Offset32>>()?,
39 tsb_mapping_offset: s.read::<Option<Offset32>>()?,
40 bsb_mapping_offset: s.read::<Option<Offset32>>()?,
41 vorg_mapping_offset: s.read::<Option<Offset32>>()?,
42 })
43 }
44
45 /// Returns the advance height offset for a glyph.
46 #[inline]
47 pub fn advance_offset(
48 &self,
49 glyph_id: GlyphId,
50 coordinates: &[NormalizedCoordinate],
51 ) -> Option<f32> {
52 let (outer_idx, inner_idx) = if let Some(offset) = self.advance_height_mapping_offset {
53 DeltaSetIndexMap::new(self.data.get(offset.to_usize()..)?).map(glyph_id.0 as u32)?
54 } else {
55 // 'If there is no delta-set index mapping table for advance widths,
56 // then glyph IDs implicitly provide the indices:
57 // for a given glyph ID, the delta-set outer-level index is zero,
58 // and the glyph ID is the delta-set inner-level index.'
59 (0, glyph_id.0)
60 };
61
62 self.variation_store
63 .parse_delta(outer_idx, inner_idx, coordinates)
64 }
65
66 /// Returns the top side bearing offset for a glyph.
67 #[inline]
68 pub fn top_side_bearing_offset(
69 &self,
70 glyph_id: GlyphId,
71 coordinates: &[NormalizedCoordinate],
72 ) -> Option<f32> {
73 let set_data = self.data.get(self.tsb_mapping_offset?.to_usize()..)?;
74 self.side_bearing_offset(glyph_id, coordinates, set_data)
75 }
76
77 /// Returns the bottom side bearing offset for a glyph.
78 #[inline]
79 pub fn bottom_side_bearing_offset(
80 &self,
81 glyph_id: GlyphId,
82 coordinates: &[NormalizedCoordinate],
83 ) -> Option<f32> {
84 let set_data = self.data.get(self.bsb_mapping_offset?.to_usize()..)?;
85 self.side_bearing_offset(glyph_id, coordinates, set_data)
86 }
87
88 /// Returns the vertical origin offset for a glyph.
89 #[inline]
90 pub fn vertical_origin_offset(
91 &self,
92 glyph_id: GlyphId,
93 coordinates: &[NormalizedCoordinate],
94 ) -> Option<f32> {
95 let set_data = self.data.get(self.vorg_mapping_offset?.to_usize()..)?;
96 self.side_bearing_offset(glyph_id, coordinates, set_data)
97 }
98
99 fn side_bearing_offset(
100 &self,
101 glyph_id: GlyphId,
102 coordinates: &[NormalizedCoordinate],
103 set_data: &[u8],
104 ) -> Option<f32> {
105 let (outer_idx, inner_idx) = DeltaSetIndexMap::new(set_data).map(glyph_id.0 as u32)?;
106 self.variation_store
107 .parse_delta(outer_idx, inner_idx, coordinates)
108 }
109}
110
111impl core::fmt::Debug for Table<'_> {
112 fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
113 write!(f, "Table {{ ... }}")
114 }
115}
116