The 'maxp' table

General table information

The 'maxp' table establishes the memory requirements for a font. It begins with a table version number. The next entry is the number of glyphs in the font. The remaining entries all establish maximum values for a number of parameters. Most of these are self explanatory. A few, however, need some clarification. The maxSizeOfInstructions is the maximum size in bytes for all of the instructions associated with a particular glyph. The maxComponentElements field refers to the maximum number of simple glyphs that will be used to create a compound glyph. The maxComponentDepth refers to the number of levels of recursion used in constructing the most complex compound glyph. In TrueType 1.0, the maximum legal value for maxComponentDepth is one. If there are no components within components, all compound glyphs can be deemed simple and this field can be set to the value one.

Table 35 : 'maxp' table

Type	Name	Description
Fixed	version	0x00010000 (1.0)
uint16	numGlyphs	the number of glyphs in the font
uint16	maxPoints	points in non-compound glyph
uint16	maxContours	contours in non-compound glyph
uint16	maxComponentPoints	points in compound glyph
uint16	maxComponentContours	contours in compound glyph
uint16	maxZones	set to 2
uint16	maxTwilightPoints	points used in Twilight Zone (Z0)
uint16	maxStorage	number of Storage Area locations
uint16	maxFunctionDefs	number of FDEFs
uint16	maxInstructionDefs	number of IDEFs
uint16	maxStackElements	maximum stack depth
uint16	maxSizeOfInstructions	byte count for glyph instructions
uint16	maxComponentElements	number of glyphs referenced at top level
uint16	maxComponentDepth	levels of recursion, set to 0 if font has only simple glyphs

Mac OS-specific information

The contents of the 'maxp' table are heavily used by all Mac OS TrueType scalars.

Newton-specific information

The 'maxp' table is required on the Newton OS.

Dependencies

The 'maxp' table contains a count for the number of glyphs in the font. Whenever this value changes, other tables which depend on it should also be updated. The tables affected includes:

• The glyph location table ('loca')
• The glyph data table ('glyf')
• The 'Zapf' table

In addition, some tables contain glyph indices which might need to be updated if a glyph is removed from the font. A partial list of such tables is:

• The character-glyph mapping table ('cmap')

Tools

Editing of the 'maxp' table is possible using TrueEdit. Other tools will alter its contents as a side effect of work that they do.

Change Log

14 September 2000

Added partial list of tables dependent on the 'maxp' table contents.

1 October 1996

Created unified TrueType book.

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