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Overlapping Glyphs Feature Type

The overlapping glyphs feature type (kOverlappingCharactersType) controls whether long tails on glyphs are permitted to collide with other glyphs. 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”, as shown in Figure B-17.

Figure B-17 shows text that allows and prevents glyph overlap. The first line does not prevent glyph overlap whereas the second line does. Preventing glyph overlap means that the script “Q” can remain because the following “u” has no descender to collide with it, whereas the script “L” is replaced with a simpler form to avoid collision with the “y”.

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 overlap, ATSUI substitutes a non-overlapping form of the glyph. Table B-20 lists the selectors that turn the overlapping glyphs feature type on and off. It is a contextual feature.

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