Fetches the MathVariants table for the specified font and returns the
minimum overlap of connecting glyphs that are required to draw a glyph
assembly in the specified direction.
<note>The direction parameter is only used to select between horizontal
or vertical directions for the construction. Even though all #hb_direction_t
values are accepted, only the result of #HB_DIRECTION_IS_HORIZONTAL is
considered.</note>
Fetches the MathVariants table for the specified font and returns the minimum overlap of connecting glyphs that are required to draw a glyph assembly in the specified direction.
<note>The direction parameter is only used to select between horizontal or vertical directions for the construction. Even though all #hb_direction_t values are accepted, only the result of #HB_DIRECTION_IS_HORIZONTAL is considered.</note>