Vertical form substitution using the 'mort' table

A special version of the glyph metamorphosis table ('mort') was defined for use under certain FE versions of Windows 3.1. Although Microsoft recommends the 'GSUB' table, font vendors may still wish to include a 'mort' table in their fonts for backwards compatibility. Future versions of Windows will support only 'GSUB'.

As with 'GSUB', GDI recognizes only a very specific implementation of 'mort'. The majority of the table will be constants to specify vertical character substitution only.

Type	Name	Contents
	(constants)	0x000100000000000100000001
Uint32	length1	Length of the whole table - 8
	(constants)	0x000300010003000000000001FFFFFFFF
	(constants)	0x0003000100000000FFFFFFFE00080000
	(constants)	0x0000000000000000
Uint16	length2	Length of the whole table - 0x38
	(constants)	0x8004000000010006
BinSrchHeader	binSrchHeader	Binary Search Header
LookupSingle	entries[n]	Actual lookup entries, sorted by glyph index

BinSrchHeader

Type	Name	Contents
Uint16	entrySize	Size in bytes of a lookup entry (set to 4)
Uint16	nEntries	Number of lookup entries to be searched
Uint16	searchRange	entrySize * (largest power of 2 less than or equal to nEntries)
Uint16	entrySelector	log2 of (largest power of 2 less than or equal to nEntries)
Uint16	rangeShift	entrySize * (nEntries - largest power of 2 less than or equal to nEntries)

LookupSingle

Type	Name	Contents
GlyphID	glyphid1	The glyph index for the horizontal shape
GlyphID	glyphid2	The glyph index for the vertical shape

The last lookup entry must be a sentinel with glyphid1=glyphid2=0xFFFF. The glyph sets should be exactly the same as those in 'GSUB'.