Struct BlendState

pub struct BlendState<'a> { /* private fields */ }

State for processing the blend operator for DICTs and charstrings.

To avoid allocation, scalars are computed on demand but this can be prohibitively expensive in charstrings where blends are applied to large numbers of elements. To amortize the cost, a fixed number of precomputed scalars are stored internally and the overflow is computed as needed.

The MAX_PRECOMPUTED_SCALARS constant determines the size of the internal buffer (currently 16).

See https://learn.microsoft.com/en-us/typography/opentype/spec/cff2charstr#45-variation-data-operators

Implementations

impl<'a> BlendState<'a>

pub fn new( store: TableRef<'a, ItemVariationStoreMarker>, coords: &'a [F2Dot14], store_index: u16, ) -> Result<BlendState<'a>, Error>

pub fn set_store_index(&mut self, store_index: u16) -> Result<(), Error>

Sets the active variation store index.

This should be called with the operand of the vsindex operator for both DICTs and charstrings.

pub fn region_count(&self) -> Result<usize, Error>

Returns the number of variation regions for the currently active variation store index.

pub fn scalars( &self, ) -> Result<impl Iterator<Item = Result<Fixed, Error>>, Error>

Returns an iterator yielding scalars for each variation region of the currently active variation store index.