Static kCTFontMatrixAttribute 

pub unsafe static kCTFontMatrixAttribute: &'static CFString

Available on crate feature CTFontDescriptor only.

kCTFontMatrixAttribute

The font transformation matrix.

This key is used to specify the font transformation matrix when creating a font. The default value is CGAffineTransformIdentity. The value for this key is a CFDataRef containing a CGAffineTransform, of which only the a, b, c, and d fields are used.

See also Apple’s documentation