read-fonts 0.39.1

//! The [Font Variations](https://docs.microsoft.com/en-us/typography/opentype/spec/fvar) table

include!("../../generated/generated_fvar.rs");

#[path = "./instance_record.rs"]
mod instance_record;

use super::{avar::Avar, variations::DeltaSetIndex};
use alloc::vec::Vec;

pub use instance_record::InstanceRecord;

const MAX_INLINE_AVAR2_AXES: usize = 64;

#[inline]
fn round_f64_to_i32(value: f64) -> i32 {
    if value >= 0.0 {
        (value + 0.5) as i32
    } else {
        (value - 0.5) as i32
    }
}

#[inline]
fn apply_avar2_delta(coord: Fixed, delta_2dot14: f64) -> Fixed {
    // HarfBuzz keeps the avar1 result in 16.16 through the avar2 add, and
    // converts the avar2 delta from 2.14 units by multiplying by four.
    Fixed::from_bits(
        coord
            .to_bits()
            .wrapping_add(round_f64_to_i32(delta_2dot14 * 4.0)),
    )
}

fn normalize_user_coords<T>(
    axes: &[VariationAxisRecord],
    user_coords: impl IntoIterator<Item = (Tag, Fixed)>,
    coords: &mut [T],
    convert: impl Fn(Fixed) -> T,
) {
    for user_coord in user_coords {
        // To permit non-linear interpolation, iterate over all axes to ensure we match
        // multiple axes with the same tag:
        // https://github.com/PeterConstable/OT_Drafts/blob/master/NLI/UnderstandingNLI.md
        // We accept quadratic behavior here to avoid dynamic allocation and with the assumption
        // that fonts contain a relatively small number of axes.
        for (axis, coord) in axes
            .iter()
            .zip(coords.iter_mut())
            .filter(|(axis, _)| axis.axis_tag() == user_coord.0)
        {
            *coord = convert(axis.normalize(user_coord.1));
        }
    }
}

fn apply_avar_mappings<T>(
    avar: Option<&Avar>,
    coords: &mut [T],
    to_fixed: impl Fn(&T) -> Fixed,
    from_fixed: impl Fn(Fixed) -> T,
) {
    let avar_mappings = avar.map(|avar| avar.axis_segment_maps());
    for (i, coord) in coords.iter_mut().enumerate() {
        if let Some(mapping) = avar_mappings
            .as_ref()
            .and_then(|mappings| mappings.get(i).transpose().ok())
            .flatten()
        {
            *coord = from_fixed(mapping.apply(to_fixed(coord)));
        }
    }
}

fn to_normalized_coords(fixed_coords: &[Fixed], normalized_coords: &mut [F2Dot14]) {
    for (target_coord, coord) in normalized_coords.iter_mut().zip(fixed_coords.iter()) {
        *target_coord = coord.to_f2dot14();
    }
}

impl<'a> Fvar<'a> {
    /// Returns the array of variation axis records.
    pub fn axes(&self) -> Result<&'a [VariationAxisRecord], ReadError> {
        Ok(self.axis_instance_arrays()?.axes())
    }

    /// Returns the array of instance records.
    pub fn instances(&self) -> Result<ComputedArray<'a, InstanceRecord<'a>>, ReadError> {
        Ok(self.axis_instance_arrays()?.instances())
    }

    /// Converts user space coordinates provided by an unordered iterator
    /// of `(tag, value)` pairs to normalized coordinates in axis list order.
    ///
    /// Stores the resulting normalized coordinates in the given slice.
    ///
    /// * User coordinate tags that don't match an axis are ignored.
    /// * User coordinate values are clamped to the range of their associated
    ///   axis before normalization.
    /// * If more than one user coordinate is provided for the same tag, the
    ///   last one is used.
    /// * If no user coordinate for an axis is provided, the associated
    ///   coordinate is set to the normalized value 0.0, representing the
    ///   default location in variation space.
    /// * The length of `normalized_coords` should equal the number of axes
    ///   present in the this table. If the length is smaller, axes at
    ///   out of bounds indices are ignored. If the length is larger, the
    ///   excess entries will be filled with zeros.
    ///
    /// If the [`Avar`] table is provided, applies remapping of coordinates
    /// according to the specification.
    pub fn user_to_normalized(
        &self,
        avar: Option<&Avar>,
        user_coords: impl IntoIterator<Item = (Tag, Fixed)>,
        normalized_coords: &mut [F2Dot14],
    ) {
        normalized_coords.fill(F2Dot14::ZERO);
        let axes = self.axes().unwrap_or_default();
        let actual_len = axes.len().min(normalized_coords.len());
        let normalized_coords = &mut normalized_coords[..actual_len];

        let mut stack_fixed_coords = [Fixed::ZERO; MAX_INLINE_AVAR2_AXES];
        let mut heap_fixed_coords = Vec::new();
        let fixed_coords = if actual_len > MAX_INLINE_AVAR2_AXES {
            heap_fixed_coords.resize(actual_len, Fixed::ZERO);
            heap_fixed_coords.as_mut_slice()
        } else {
            &mut stack_fixed_coords[..actual_len]
        };
        normalize_user_coords(axes, user_coords, fixed_coords, core::convert::identity);
        apply_avar_mappings(avar, fixed_coords, |coord| *coord, core::convert::identity);

        let Some(avar) = avar else {
            to_normalized_coords(fixed_coords, normalized_coords);
            return;
        };
        if avar.version() == MajorMinor::VERSION_1_0 {
            to_normalized_coords(fixed_coords, normalized_coords);
            return;
        }

        let var_store = avar.var_store();
        let var_index_map = avar.axis_index_map();

        let mut coords_2dot14 = [F2Dot14::ZERO; MAX_INLINE_AVAR2_AXES];
        let coords_2dot14 = &mut coords_2dot14[..actual_len];
        for (coord_2dot14, coord) in coords_2dot14.iter_mut().zip(fixed_coords.iter()) {
            *coord_2dot14 = coord.to_f2dot14();
        }

        if let Some(Ok(varstore)) = var_store.as_ref() {
            for (i, coord) in fixed_coords.iter_mut().enumerate() {
                let var_index = if let Some(Ok(ref map)) = var_index_map {
                    match map.get(i as u32) {
                        Ok(index) => index,
                        Err(_) => continue,
                    }
                } else {
                    DeltaSetIndex {
                        outer: 0,
                        inner: i as u16,
                    }
                };
                if let Ok(delta) = varstore.compute_float_delta(var_index, coords_2dot14) {
                    *coord =
                        apply_avar2_delta(*coord, delta.to_f64()).clamp(Fixed::NEG_ONE, Fixed::ONE);
                }
            }
        }

        to_normalized_coords(fixed_coords, normalized_coords);
    }
}

impl VariationAxisRecord {
    /// Returns a normalized coordinate for the given value.
    pub fn normalize(&self, mut value: Fixed) -> Fixed {
        use core::cmp::Ordering::*;
        let min_value = self.min_value();
        let default_value = self.default_value();
        // Make sure max is >= min to avoid potential panic in clamp.
        let max_value = self.max_value().max(min_value);
        value = value.clamp(min_value, max_value);
        value = match value.cmp(&default_value) {
            Less => {
                -((default_value.saturating_sub(value)) / (default_value.saturating_sub(min_value)))
            }
            Greater => {
                (value.saturating_sub(default_value)) / (max_value.saturating_sub(default_value))
            }
            Equal => Fixed::ZERO,
        };
        value.clamp(Fixed::NEG_ONE, Fixed::ONE)
    }
}

#[cfg(test)]
mod tests {
    use crate::{FontRef, TableProvider};
    use types::{F2Dot14, Fixed, NameId, Tag};

    #[test]
    fn axes() {
        let font = FontRef::new(font_test_data::VAZIRMATN_VAR).unwrap();
        let fvar = font.fvar().unwrap();
        assert_eq!(fvar.axis_count(), 1);
        let wght = &fvar.axes().unwrap().first().unwrap();
        assert_eq!(wght.axis_tag(), Tag::new(b"wght"));
        assert_eq!(wght.min_value(), Fixed::from_f64(100.0));
        assert_eq!(wght.default_value(), Fixed::from_f64(400.0));
        assert_eq!(wght.max_value(), Fixed::from_f64(900.0));
        assert_eq!(wght.flags(), 0);
        assert_eq!(wght.axis_name_id(), NameId::new(257));
    }

    #[test]
    fn instances() {
        let font = FontRef::new(font_test_data::VAZIRMATN_VAR).unwrap();
        let fvar = font.fvar().unwrap();
        assert_eq!(fvar.instance_count(), 9);
        // There are 9 instances equally spaced from 100.0 to 900.0
        // with name id monotonically increasing starting at 258.
        let instances = fvar.instances().unwrap();
        for i in 0..9 {
            let value = 100.0 * (i + 1) as f64;
            let name_id = NameId::new(258 + i as u16);
            let instance = instances.get(i).unwrap();
            assert_eq!(instance.coordinates.len(), 1);
            assert_eq!(
                instance.coordinates.first().unwrap().get(),
                Fixed::from_f64(value)
            );
            assert_eq!(instance.subfamily_name_id, name_id);
            assert_eq!(instance.post_script_name_id, None);
        }
    }

    #[test]
    fn normalize() {
        let font = FontRef::new(font_test_data::VAZIRMATN_VAR).unwrap();
        let fvar = font.fvar().unwrap();
        let axis = fvar.axes().unwrap().first().unwrap();
        let values = [100.0, 220.0, 250.0, 400.0, 650.0, 900.0];
        let expected = [-1.0, -0.60001, -0.5, 0.0, 0.5, 1.0];
        for (value, expected) in values.into_iter().zip(expected) {
            assert_eq!(
                axis.normalize(Fixed::from_f64(value)),
                Fixed::from_f64(expected)
            );
        }
    }

    #[test]
    fn normalize_overflow() {
        // From: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=69787
        // & https://oss-fuzz.com/testcase?key=6159008335986688
        // fvar entry triggering overflow:
        // min: -26335.87451171875 def 8224.12548828125 max 8224.12548828125
        let test_case = &[
            79, 84, 84, 79, 0, 1, 32, 32, 255, 32, 32, 32, 102, 118, 97, 114, 32, 32, 32, 32, 0, 0,
            0, 28, 0, 0, 0, 41, 32, 0, 0, 0, 0, 1, 32, 32, 0, 2, 32, 32, 32, 32, 0, 0, 32, 32, 32,
            32, 32, 0, 0, 0, 0, 153, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32,
        ];
        let font = FontRef::new(test_case).unwrap();
        let fvar = font.fvar().unwrap();
        let axis = fvar.axes().unwrap()[1];
        // Should not panic with "attempt to subtract with overflow".
        assert_eq!(
            axis.normalize(Fixed::from_f64(0.0)),
            Fixed::from_f64(-0.2509765625)
        );
    }

    #[test]
    fn user_to_normalized() {
        let font = FontRef::from_index(font_test_data::VAZIRMATN_VAR, 0).unwrap();
        let fvar = font.fvar().unwrap();
        let avar = font.avar().ok();
        let wght = Tag::new(b"wght");
        let axis = fvar.axes().unwrap()[0];
        let mut normalized_coords = [F2Dot14::default(); 1];
        // avar table maps 0.8 to 0.83875
        let avar_user = axis.default_value().to_f32()
            + (axis.max_value().to_f32() - axis.default_value().to_f32()) * 0.8;
        let avar_normalized = 0.83875;
        #[rustfmt::skip]
        let cases = [
            // (user, normalized)
            (-1000.0, -1.0f32),
            (100.0, -1.0),
            (200.0, -0.5),
            (400.0, 0.0),
            (900.0, 1.0),
            (avar_user, avar_normalized),
            (1251.5, 1.0),
        ];
        for (user, normalized) in cases {
            fvar.user_to_normalized(
                avar.as_ref(),
                [(wght, Fixed::from_f64(user as f64))],
                &mut normalized_coords,
            );
            assert_eq!(normalized_coords[0], F2Dot14::from_f32(normalized));
        }
    }

    #[test]
    fn avar2() {
        let font = FontRef::new(font_test_data::AVAR2_CHECKER).unwrap();
        let avar = font.avar().ok();
        let fvar = font.fvar().unwrap();
        let avar_axis = Tag::new(b"AVAR");
        let avwk_axis = Tag::new(b"AVWK");
        let mut normalized_coords = [F2Dot14::default(); 2];
        let cases = [
            ((100.0, 0.0), (1.0, 1.0)),
            ((50.0, 0.0), (0.5, 0.5)),
            ((0.0, 50.0), (0.0, 0.5)),
        ];
        for (user, expected) in cases {
            fvar.user_to_normalized(
                avar.as_ref(),
                [
                    (avar_axis, Fixed::from_f64(user.0)),
                    (avwk_axis, Fixed::from_f64(user.1)),
                ],
                &mut normalized_coords,
            );
            assert_eq!(normalized_coords[0], F2Dot14::from_f32(expected.0));
            assert_eq!(normalized_coords[1], F2Dot14::from_f32(expected.1));
        }
    }

    #[test]
    fn avar2_no_panic_with_wrong_size_coords_array() {
        // this font has 2 axes
        let font = FontRef::new(font_test_data::AVAR2_CHECKER).unwrap();
        let avar = font.avar().ok();
        let fvar = font.fvar().unwrap();
        // output array too small
        let mut normalized_coords = [F2Dot14::default(); 1];
        fvar.user_to_normalized(avar.as_ref(), [], &mut normalized_coords);
        // output array too large
        let mut normalized_coords = [F2Dot14::default(); 4];
        fvar.user_to_normalized(avar.as_ref(), [], &mut normalized_coords);
    }

    #[test]
    fn avar2_preserves_16_16_precision_until_final_rounding() {
        // Quantizing to 2.14 before applying the avar2 delta would produce 0x0002
        // here, but HarfBuzz's 16.16 path produces 0x0001.
        let coord = Fixed::from_bits(3);
        assert_eq!(
            super::apply_avar2_delta(coord, 0.5).to_f2dot14(),
            F2Dot14::from_bits(1)
        );
    }

    #[test]
    fn avar2_clamps_hidden_axis_for_amstelvar_repro() {
        let font = FontRef::new(font_test_data::AMSTELVAR_AVAR2_A).unwrap();
        let avar = font.avar().ok();
        let fvar = font.fvar().unwrap();
        let mut normalized_coords = [F2Dot14::ZERO; 12];

        fvar.user_to_normalized(
            avar.as_ref(),
            [(Tag::new(b"wght"), Fixed::from_f64(1000.0))],
            &mut normalized_coords,
        );

        assert_eq!(normalized_coords[1], F2Dot14::from_bits(-5370)); // XTRA
        assert_eq!(normalized_coords[2], F2Dot14::ONE); // XOPQ clamped from > 1
        assert_eq!(normalized_coords[3], F2Dot14::from_bits(2254)); // YOPQ
        assert_eq!(normalized_coords[11], F2Dot14::ONE); // wght
    }
}