Struct FontShaper 

pub struct FontShaper { /* private fields */ }

Shapes Hudum with the bundled mongfontbuilder font through HarfBuzz rules — the font backend of the crate (Cargo feature font), an alternative to the rule engine Shaper.

harfrust (the Rust port of HarfBuzz) runs the Hudum font that mongfontbuilder — the reference implementation of UTN #57 — composes, with the OpenType rules the composer generates. The crate reads the written units off the glyphs the font chose. The font is bundled without its outlines (fonts/hudum.otf, 30 KB: GSUB, GDEF, cmap and the sfnt skeleton), and the glyph → written-unit table is generated from its glyph names.

Compared with the rule engine:

• the rules are the font’s, at the mongfontbuilder commit fonts/mongfontbuilder.json pins — not a port. Where the two disagree, this is what the font draws;
• there is no trace or shape_detailed: the font’s lookups are not the crate’s rules. The glyph-level view is FontShaper::shape_glyphs;
• there is no normalize: the normalizer is built on the rule engine;
• it costs harfrust and its crates, Rust 1.85, and a few microseconds per word.

Output contract

FontShaper::shape is the same kind of sequence as Shaper::shape: Mvs and Nirugu verbatim, a Zwj only where it changes the ink, the duplicate encodings unified — the two post-passes are shared with the rule engine — so the two backends can be compared unit for unit. How the glyphs are read:

• an FVS, valid or not, is never a unit. The font draws an invalid one as a visible placeholder; the crate follows the rule engine and the GB/T 25914-2023 unit streams and reports nothing;
• an MVS that separates nothing is drawn as a space plus a silent glyph: one Mvs. An NNBSP is an Mvs, as in the rule engine;
• a ZWJ between two letters the font ligates comes out of HarfBuzz after the ligature. FontShaper::shape_raw keeps it there; shape drops it (see ShapedGlyph::skipped).

Errors

Error::NonMongolianChar on anything but Mongolian letters, FVS, MVS, NNBSP, nirugu and ZWJ — the rule engine’s rule; Error::UnsupportedChar on a character of the block the font has no glyph for: a letter of another writing system (Todo, Sibe, Manchu, Ali Gali), an Ali Gali sign, an unassigned code point. The rule engine shapes those to nothing; the font would draw its .notdef box, so this backend refuses them instead.

Example

use mongol_norm::{FontShaper, Locale, Shaper};

let font = FontShaper::new();
let rules = Shaper::new(Locale::Mng);
assert_eq!(font.shape_str("ᠰᠠᠢᠨ")?, "S+A+I+I+A");
assert_eq!(font.shape("ᠰᠠᠢᠨ")?, rules.shape("ᠰᠠᠢᠨ")?);

Implementations

impl FontShaper

pub fn new() -> FontShaper

A shaper over the bundled font.

The font is parsed once per process and shared; a shaper holds its shape plan, so it is cheap to keep and shapes without further setup.

pub fn shape(&self, text: &str) -> Result<Vec<WrittenUnit>, Error>

Shape text into its written-unit sequence, on the same contract as Shaper::shape: Mvs and Nirugu verbatim, a Zwj only where it changes the ink, the duplicate encodings unified.

pub fn shape_str(&self, text: &str) -> Result<String, Error>

FontShaper::shape joined with + (S+A+I+I+A), the CLI’s output format.

pub fn same_shape(&self, a: &str, b: &str) -> Result<bool, Error>

Do a and b render the same glyph sequence?

pub fn shape_glyphs(&self, text: &str) -> Result<Vec<ShapedGlyph>, Error>

The glyphs the font chose for text, in the order HarfBuzz returns them, each with its written units and positions — the debugging view of this backend.

Trait Implementations

impl Default for FontShaper

fn default() -> FontShaper

Returns the “default value” for a type.