read_fonts/tables/
avar.rs

1//! The [Axis Variations](https://docs.microsoft.com/en-us/typography/opentype/spec/avar) table
2
3use super::variations::{DeltaSetIndexMap, ItemVariationStore};
4
5include!("../../generated/generated_avar.rs");
6
7impl SegmentMaps<'_> {
8    /// Applies the piecewise linear mapping to the specified coordinate.
9    pub fn apply(&self, coord: Fixed) -> Fixed {
10        let mut prev = AxisValueMap {
11            from_coordinate: Default::default(),
12            to_coordinate: Default::default(),
13        };
14        for (i, axis_value_map) in self.axis_value_maps().iter().enumerate() {
15            use core::cmp::Ordering::*;
16            let from = axis_value_map.from_coordinate().to_fixed();
17            match from.cmp(&coord) {
18                Equal => return axis_value_map.to_coordinate().to_fixed(),
19                Greater => {
20                    if i == 0 {
21                        return coord;
22                    }
23                    let to = axis_value_map.to_coordinate().to_fixed();
24                    let prev_from = prev.from_coordinate().to_fixed();
25                    let prev_to = prev.to_coordinate().to_fixed();
26                    return prev_to + (to - prev_to).mul_div(coord - prev_from, from - prev_from);
27                }
28                _ => {}
29            }
30            prev = *axis_value_map;
31        }
32        coord
33    }
34}
35
36impl VarSize for SegmentMaps<'_> {
37    type Size = u16;
38
39    fn read_len_at(data: FontData, pos: usize) -> Option<usize> {
40        Some(
41            data.read_at::<u16>(pos).ok()? as usize * AxisValueMap::RAW_BYTE_LEN
42                + u16::RAW_BYTE_LEN,
43        )
44    }
45}
46
47impl<'a> FontRead<'a> for SegmentMaps<'a> {
48    fn read(data: FontData<'a>) -> Result<Self, ReadError> {
49        let mut cursor = data.cursor();
50        let position_map_count: BigEndian<u16> = cursor.read_be()?;
51        let axis_value_maps = cursor.read_array(position_map_count.get() as _)?;
52        Ok(SegmentMaps {
53            position_map_count,
54            axis_value_maps,
55        })
56    }
57}
58
59#[cfg(test)]
60mod tests {
61
62    use font_test_data::bebuffer::BeBuffer;
63
64    use super::*;
65    use crate::{FontRef, TableProvider};
66
67    fn value_map(from: f32, to: f32) -> [F2Dot14; 2] {
68        [F2Dot14::from_f32(from), F2Dot14::from_f32(to)]
69    }
70
71    // for the purpose of testing it is easier for us to use an array
72    // instead of a concrete type, since we can write that into BeBuffer
73    impl PartialEq<[F2Dot14; 2]> for AxisValueMap {
74        fn eq(&self, other: &[F2Dot14; 2]) -> bool {
75            self.from_coordinate == other[0] && self.to_coordinate == other[1]
76        }
77    }
78
79    #[test]
80    fn segment_maps() {
81        let font = FontRef::new(font_test_data::VAZIRMATN_VAR).unwrap();
82        let avar = font.avar().unwrap();
83        assert_eq!(avar.axis_count(), 1);
84        let expected_segment_maps = &[vec![
85            value_map(-1.0, -1.0),
86            value_map(-0.6667, -0.5),
87            value_map(-0.3333, -0.25),
88            value_map(0.0, 0.0),
89            value_map(0.2, 0.3674),
90            value_map(0.4, 0.52246),
91            value_map(0.6, 0.67755),
92            value_map(0.8, 0.83875),
93            value_map(1.0, 1.0),
94        ]];
95        let segment_maps = avar
96            .axis_segment_maps()
97            .iter()
98            .map(|segment_map| segment_map.unwrap().axis_value_maps().to_owned())
99            .collect::<Vec<_>>();
100        assert_eq!(segment_maps, expected_segment_maps);
101    }
102
103    #[test]
104    fn segment_maps_multi_axis() {
105        let segment_one_maps = [
106            value_map(-1.0, -1.0),
107            value_map(-0.6667, -0.5),
108            value_map(-0.3333, -0.25),
109        ];
110        let segment_two_maps = [value_map(0.8, 0.83875), value_map(1.0, 1.0)];
111
112        let data = BeBuffer::new()
113            .push(MajorMinor::VERSION_1_0)
114            .push(0u16) // reserved
115            .push(2u16) // axis count
116            // segment map one
117            .push(3u16) // position count
118            .extend(segment_one_maps[0])
119            .extend(segment_one_maps[1])
120            .extend(segment_one_maps[2])
121            // segment map two
122            .push(2u16) // position count
123            .extend(segment_two_maps[0])
124            .extend(segment_two_maps[1]);
125
126        let avar = super::Avar::read(data.data().into()).unwrap();
127        assert_eq!(avar.axis_segment_maps().iter().count(), 2);
128        assert_eq!(
129            avar.axis_segment_maps()
130                .get(0)
131                .unwrap()
132                .unwrap()
133                .axis_value_maps,
134            segment_one_maps,
135        );
136        assert_eq!(
137            avar.axis_segment_maps()
138                .get(1)
139                .unwrap()
140                .unwrap()
141                .axis_value_maps,
142            segment_two_maps,
143        );
144    }
145
146    #[test]
147    fn piecewise_linear() {
148        let font = FontRef::new(font_test_data::VAZIRMATN_VAR).unwrap();
149        let avar = font.avar().unwrap();
150        let segment_map = avar.axis_segment_maps().get(0).unwrap().unwrap();
151        let coords = [-1.0, -0.5, 0.0, 0.5, 1.0];
152        let expected_result = [-1.0, -0.375, 0.0, 0.600006103515625, 1.0];
153        assert_eq!(
154            &expected_result[..],
155            &coords
156                .iter()
157                .map(|coord| segment_map.apply(Fixed::from_f64(*coord)).to_f64())
158                .collect::<Vec<_>>()
159        );
160    }
161
162    #[test]
163    fn avar2() {
164        let font = FontRef::new(font_test_data::AVAR2_CHECKER).unwrap();
165        let avar = font.avar().unwrap();
166        assert_eq!(avar.version(), MajorMinor::VERSION_2_0);
167        assert!(avar.axis_index_map_offset().is_some());
168        assert!(avar.var_store_offset().is_some());
169        assert!(avar.var_store().is_some());
170    }
171}
read_fonts/tables/avar.rs

read_fonts/tables/
avar.rs
