NSFont defines two special glyphs. NullGlyph
indicates
no glyph at all and is useful in some layout methods for calculating
information that isn’t relative to another glyph. For example
in Objective-C, with positionOfGlyph:precededByGlyph:isNominal:
,
you can specify NSNullGlyph
as the
first argument to get the nominal advancement of the preceding glyph.
The other special glyph is ControlGlyph
,
which the text system maps onto control functions such as linefeed
and tab. This glyph has no graphic representation and has no inherent advancement
of its own. Instead, the text system examines the control character underlying
the glyph to determine what kind of special layout it needs to perform.
© 1997, 2008 Apple Inc. All Rights Reserved. (Last updated: 2008-02-08)