ttf_parser/tables/
hvar.rs

1//! A [Horizontal 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 [Horizontal 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_width_mapping_offset: Option<Offset32>,
16    lsb_mapping_offset: Option<Offset32>,
17    rsb_mapping_offset: Option<Offset32>,
18}
19
20impl<'a> Table<'a> {
21    /// Parses a table from raw data.
22    pub fn parse(data: &'a [u8]) -> Option<Self> {
23        let mut s = Stream::new(data);
24
25        let version = s.read::<u32>()?;
26        if version != 0x00010000 {
27            return None;
28        }
29
30        let variation_store_offset = s.read::<Offset32>()?;
31        let var_store_s = Stream::new_at(data, variation_store_offset.to_usize())?;
32        let variation_store = ItemVariationStore::parse(var_store_s)?;
33
34        Some(Table {
35            data,
36            variation_store,
37            advance_width_mapping_offset: s.read::<Option<Offset32>>()?,
38            lsb_mapping_offset: s.read::<Option<Offset32>>()?,
39            rsb_mapping_offset: s.read::<Option<Offset32>>()?,
40        })
41    }
42
43    /// Returns the advance width offset for a glyph.
44    #[inline]
45    pub fn advance_offset(
46        &self,
47        glyph_id: GlyphId,
48        coordinates: &[NormalizedCoordinate],
49    ) -> Option<f32> {
50        let (outer_idx, inner_idx) = if let Some(offset) = self.advance_width_mapping_offset {
51            DeltaSetIndexMap::new(self.data.get(offset.to_usize()..)?).map(glyph_id.0 as u32)?
52        } else {
53            // 'If there is no delta-set index mapping table for advance widths,
54            // then glyph IDs implicitly provide the indices:
55            // for a given glyph ID, the delta-set outer-level index is zero,
56            // and the glyph ID is the delta-set inner-level index.'
57            (0, glyph_id.0)
58        };
59
60        self.variation_store
61            .parse_delta(outer_idx, inner_idx, coordinates)
62    }
63
64    /// Returns the left side bearing offset for a glyph.
65    #[inline]
66    pub fn left_side_bearing_offset(
67        &self,
68        glyph_id: GlyphId,
69        coordinates: &[NormalizedCoordinate],
70    ) -> Option<f32> {
71        let set_data = self.data.get(self.lsb_mapping_offset?.to_usize()..)?;
72        self.side_bearing_offset(glyph_id, coordinates, set_data)
73    }
74
75    /// Returns the right side bearing offset for a glyph.
76    #[inline]
77    pub fn right_side_bearing_offset(
78        &self,
79        glyph_id: GlyphId,
80        coordinates: &[NormalizedCoordinate],
81    ) -> Option<f32> {
82        let set_data = self.data.get(self.rsb_mapping_offset?.to_usize()..)?;
83        self.side_bearing_offset(glyph_id, coordinates, set_data)
84    }
85
86    fn side_bearing_offset(
87        &self,
88        glyph_id: GlyphId,
89        coordinates: &[NormalizedCoordinate],
90        set_data: &[u8],
91    ) -> Option<f32> {
92        let (outer_idx, inner_idx) = DeltaSetIndexMap::new(set_data).map(glyph_id.0 as u32)?;
93        self.variation_store
94            .parse_delta(outer_idx, inner_idx, coordinates)
95    }
96}
97
98impl core::fmt::Debug for Table<'_> {
99    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
100        write!(f, "Table {{ ... }}")
101    }
102}
ttf_parser/tables/hvar.rs

ttf_parser/tables/
hvar.rs
