Vendor things

third-party/vendor/ttf-parser-0.15.2/src/tables/hvar.rs

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+//! A [Horizontal/Vertical Metrics Variations Table](
+//! https://docs.microsoft.com/en-us/typography/opentype/spec/hvar) implementation.
+
+use core::convert::TryFrom;
+
+use crate::{GlyphId, NormalizedCoordinate};
+use crate::parser::{Stream, Offset, Offset32};
+use crate::var_store::ItemVariationStore;
+
+struct DeltaSetIndexMap<'a> {
+    data: &'a [u8],
+}
+
+impl<'a> DeltaSetIndexMap<'a> {
+    #[inline]
+    fn new(data: &'a [u8]) -> Self {
+        DeltaSetIndexMap { data }
+    }
+
+    #[inline]
+    fn map(&self, glyph_id: GlyphId) -> Option<(u16, u16)> {
+        let mut idx = glyph_id.0;
+
+        let mut s = Stream::new(self.data);
+        let entry_format = s.read::<u16>()?;
+        let map_count = s.read::<u16>()?;
+
+        if map_count == 0 {
+            return None;
+        }
+
+        // 'If a given glyph ID is greater than mapCount-1, then the last entry is used.'
+        if idx >= map_count {
+            idx = map_count - 1;
+        }
+
+        let entry_size = ((entry_format >> 4) & 3) + 1;
+        let inner_index_bit_count = u32::from((entry_format & 0xF) + 1);
+
+        s.advance(usize::from(entry_size) * usize::from(idx));
+
+        let mut n = 0u32;
+        for b in s.read_bytes(usize::from(entry_size))? {
+            n = (n << 8) + u32::from(*b);
+        }
+
+        let outer_index = n >> inner_index_bit_count;
+        let inner_index = n & ((1 << inner_index_bit_count) - 1);
+        Some((
+            u16::try_from(outer_index).ok()?,
+            u16::try_from(inner_index).ok()?
+        ))
+    }
+}
+
+
+/// A [Horizontal/Vertical Metrics Variations Table](
+/// https://docs.microsoft.com/en-us/typography/opentype/spec/hvar).
+#[derive(Clone, Copy)]
+pub struct Table<'a> {
+    data: &'a [u8],
+    variation_store: ItemVariationStore<'a>,
+    advance_width_mapping_offset: Option<Offset32>,
+    lsb_mapping_offset: Option<Offset32>,
+}
+
+impl<'a> Table<'a> {
+    /// Parses a table from raw data.
+    pub fn parse(data: &'a [u8]) -> Option<Self> {
+        let mut s = Stream::new(data);
+
+        let version = s.read::<u32>()?;
+        if version != 0x00010000 {
+            return None;
+        }
+
+        let variation_store_offset = s.read::<Offset32>()?;
+        let var_store_s = Stream::new_at(data, variation_store_offset.to_usize())?;
+        let variation_store = ItemVariationStore::parse(var_store_s)?;
+
+        Some(Table {
+            data,
+            variation_store,
+            advance_width_mapping_offset: s.read::<Option<Offset32>>()?,
+            lsb_mapping_offset: s.read::<Option<Offset32>>()?,
+        })
+    }
+
+    /// Returns advance offset for a glyph.
+    #[inline]
+    pub fn advance_offset(
+        &self,
+        glyph_id: GlyphId,
+        coordinates: &[NormalizedCoordinate],
+    ) -> Option<f32> {
+        let (outer_idx, inner_idx) = if let Some(offset) = self.advance_width_mapping_offset {
+            DeltaSetIndexMap::new(self.data.get(offset.to_usize()..)?).map(glyph_id)?
+        } else {
+            // 'If there is no delta-set index mapping table for advance widths,
+            // then glyph IDs implicitly provide the indices:
+            // for a given glyph ID, the delta-set outer-level index is zero,
+            // and the glyph ID is the delta-set inner-level index.'
+            (0, glyph_id.0)
+        };
+
+        self.variation_store.parse_delta(outer_idx, inner_idx, coordinates)
+    }
+
+    /// Returns side bearing offset for a glyph.
+    #[inline]
+    pub fn side_bearing_offset(
+        &self,
+        glyph_id: GlyphId,
+        coordinates: &[NormalizedCoordinate],
+    ) -> Option<f32> {
+        let set_data = self.data.get(self.lsb_mapping_offset?.to_usize()..)?;
+        let (outer_idx, inner_idx) = DeltaSetIndexMap::new(set_data).map(glyph_id)?;
+        self.variation_store.parse_delta(outer_idx, inner_idx, coordinates)
+    }
+}
+
+impl core::fmt::Debug for Table<'_> {
+    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
+        write!(f, "Table {{ ... }}")
+    }
+}