White space within solids are defined anti-clockwise . However if you do choose to use them, you'll discover TrueType uses a non-zero winding fill algorithm. The Format of TrueType Outline Data Outlines for all the glyphs in a font are stored in TrueType's 'glyf' table. The format is described with extreme conciseness, in just over 4 pages of the TrueType specification . This table, containing all the glyphs in order, is indexed by the 'loca' table.
Simple glyphs contain compressed outline data and hinting instructions.
Composite glyphs refer to other glyphs for their outlines. Referenced components may be simple or composite themselves. A composite glyph inherits all the hinting in each of its components, and may be hinted further. The commonest use of composite glyphs is for the efficient representation of accented glyphs. Unfortunately in Windows 3.1 this only worked for simple cases.