Justification Priority Table

A Justification Priority (JstfPriority) table defines justification suggestions for a single priority level. Each priority level specifies whether to enable or disable GSUB and GPOS lookups or apply text justification lookups to shrink and extend lines of text.

JstfPriority has offsets to four tables with line shrinkage data: two are JstfGSUBModList tables for enabling and disabling glyph substitution lookups, and two are JstfGPOSModList tables for enabling and disabling glyph positioning lookups. Offsets to JstfGSUBModList and JstfGPOSModList tables also are defined for line extension.

Example 3 at the end of this chapter demonstrates two JstfPriority tables for two justification suggestions.

JstfPriority table

Type	Name	Description
Offset	ShrinkageEnableGSUB	Offset to Shrinkage Enable JstfGSUBModList table
		—from beginning of JstfPriority table
		—may be NULL
Offset	ShrinkageDisableGSUB	Offset to Shrinkage Disable JstfGSUBModList table
		—from beginning of JstfPriority table
		—may be NULL
Offset	ShrinkageEnableGPOS	Offset to Shrinkage Enable JstfGPOSModList table
		—from beginning of JstfPriority table
		—may be NULL
Offset	ShrinkageDisableGPOS	Offset to Shrinkage Disable JstfGPOSModList table
		—from beginning of JstfPriority table
		—may be NULL
Offset	ShrinkageJstfMax	Offset to Shrinkage JstfMax table
		—from beginning of JstfPriority table
		—may be NULL
Offset	ExtensionEnableGSUB	Offset to Extension Enable JstfGSUBModList table
		—may be NULL
Offset	ExtensionDisableGSUB	Offset to Extension Disable JstfGSUBModList table
		—from beginning of JstfPriority table
		—may be NULL
Offset	ExtensionEnableGPOS	Offset to Extension Enable JstfGSUBModList table
		—may be NULL
Offset	ExtensionDisableGPOS	Offset to Extension Disable JstfGSUBModList table
		—from beginning of JstfPriority table
		—may be NULL
Offset	ExtensionJstfMax	Offset to Extension JstfMax table
		—from beginning of JstfPriority table
		—may be NULL