Struct FaceChain 

pub struct FaceChain { /* private fields */ }

Ordered chain of faces. Index 0 is the primary; index N is consulted only if 0..N all returned .notdef for a codepoint.

Implementations

impl FaceChain

pub fn new(primary: Face) -> Self

Build a chain from a single primary face. Use FaceChain::push_fallback (chainable) to append fallbacks.

pub fn push_fallback(self, face: Face) -> Self

Append a fallback face to the end of the chain. Builder-style: FaceChain::new(latin).push_fallback(cjk).push_fallback(emoji).

pub fn len(&self) -> usize

Number of faces in the chain (including the primary).

pub fn is_empty(&self) -> bool

True if the chain has no faces — never the case for chains constructed via FaceChain::new, present only because clippy rightly complains when len() exists alone.

pub fn face(&self, idx: u16) -> &Face

Borrow face at idx. Panics if idx >= len() — the rasterizer always reads face_idx from a PositionedGlyph produced by this chain so the index is bounded by construction.

pub fn primary(&self) -> &Face

Borrow the primary face — useful for size/metric queries.

pub fn face_mut(&mut self, idx: usize) -> &mut Face

Mutably borrow face at idx. Used to flip per-face state like variation coordinates without rebuilding the chain. Panics if idx >= len().

pub fn set_variation_coords(&mut self, coords: &[f32]) -> Result<(), Error>

Set the variation coordinates on the primary face (index 0). Convenience wrapper around Face::set_variation_coords for the common case of “shape this run at wght=600 / wdth=125”. Mirrors Face::set_variation_coords’s clamp + length cap and returns its error variant unchanged.

Fallback faces in the chain are NOT touched — call FaceChain::face_mut explicitly if a fallback also needs variation coords (rare in practice; fallback faces typically cover a different script and are loaded from a static cut).

pub fn named_instances(&self, face_index: usize) -> Vec<NamedInstance>

Named instances published by the face at face_index. Empty vec when the face is static / OTF, or when the index is out of range. Mirrors Face::named_instances for the chosen face.

pub fn variation_axes(&self, face_index: usize) -> Vec<VariationAxis>

Variation axes published by the face at face_index. Empty vec when the face is static / OTF, or when the index is out of range. Mirrors Face::variation_axes for the chosen face.

pub fn shape( &self, text: &str, size_px: f32, ) -> Result<Vec<PositionedGlyph>, Error>

Shape text with full chain fallback at default style (upright, regular).

pub fn shape_styled( &self, text: &str, size_px: f32, _style: Style, ) -> Result<Vec<PositionedGlyph>, Error>

Shape text honouring style (italic / weight). The shear derived from style is applied at rasterise-time, not at shape-time — so glyph positions / advances stay identical regardless of italic. This matches what desktop shapers do (synthesised italic doesn’t change the metrics).

Trait Implementations

impl Debug for FaceChain

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

Formats the value using the given formatter.