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.

The '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

Fonts with PostScript outlines (that is, OpenType fonts with 'CFF ' tables) use a six-byte version of the 'maxp' table:

The 'maxp' Table for PostScript OpenType Fonts
Type
Name
Description
Fixed version 0x00005000 (0.5)
uint16 numGlyphs the number of glyphs in the font

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:

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: