Prevention of Glyph Overlap Font Feature Selector Constants

Some glyphs, especially certain initial swashes, have parts that extend well beyond their advance widths. An initial "Q", for example, may have a tail that extends underneath the following "u".

For fonts that support the glyph overlap feature type, you can specify that no glyph may overlap the outline of the following glyph. If it does, a non-overlapping form of the glyph is substituted. Table D-20 lists the selectors for this feature.

Table D-20 Feature selectors for the kOverlappingCharactersType feature type

Constant	Explanation
`kPreventOverlapOnSelector kPreventOverlapOffSelector`	Prevents or allows the collision of an extended part of one glyph with an adjacent glyph.

In the case of Figure D-12, for example, preventing glyph overlap means that the script "Q" can remain because the following "u" has no descenders to collide with it, whereas the script "L" is replaced with a simpler form to avoid collision with the "y".

Figure D-12 Allowing and preventing glyph overlap