Struct Kerning 

pub struct Kerning { /* private fields */ }

Parsed GPOS kern-feature pair positioning for a font.

Built once via Font::gpos_kerning; Kerning::pair is a cheap, allocation-free lookup. An empty Kerning (no GPOS / no kern feature / malformed) makes every pair() return 0.

Implementations

impl Kerning

pub fn pair(&self, left: u16, right: u16) -> i16

x-advance adjustment (font design units) applied between left and right glyph ids; 0 if no kern pair applies. First matching subtable wins.

pub fn for_each_ascii_pair( &self, glyph_of: impl Fn(u8) -> u16, emit: impl FnMut(u8, u8, i16), )

Enumerates the ASCII byte pairs this kerning adjusts, replacing the 16,384-pair brute force over Kerning::pair.

For every byte pair (l, r) with pair(glyph_of(l), glyph_of(r)) != 0 — where glyph_of maps the 128 ASCII bytes to glyph ids, possibly several bytes to one glyph — calls emit(l, r, v) with v exactly equal to that pair result (first matching subtable wins, defined zeros shadow later subtables just like pair). Pairs resolving to 0 are never emitted: a zero-initialized matrix already holds their value, so emit fires once per nonzero cell. The order of emit calls across distinct pairs is unspecified (format-1 pair maps hash-scatter), so emit must be order-independent.

Cost is proportional to what the tables actually contain — format-1 pair-map entries and format-2 coverage glyphs — instead of the full 128x128 cross product.

Trait Implementations

impl Clone for Kerning

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Kerning

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Kerning

fn default() -> Self

Returns the “default value” for a type.