Under QuickDraw GX, an end user enters characters into a line of text and Line Layout , working with information in the font, determines the appropriate glyphs to display. GX fonts can include more than 65,000 glyphs, along with information that tells Line Layout how and when to access each glyph. This manual uses the term glyph effects to refer to this information. For languages such as Hindi, certain kinds of glyph effects are essential for proper display. The section Adding Glyph Effects describes how to use TrueEdit to add glyph effects to your font.
Position effects A font's basic spacing, or metrics , defines the width and alignment of each glyph.
QuickDraw GX provides a variety of features which extend the spacing capabilities of a font. The term position effects encompasses all the information included in a GX font which determines the placement of glyphs relative to each other on a line. After Line Layout uses a font's glyph effects to determine which glyphs to display, it uses the position effects to determine their arrangement. Position effects can be applied to all glyphs in the font, or triggered by a specific context. Kerning information can be added to a GX font in several forms for flexibility.