Sorry, > > To establish a new default value for a graphics state variable, it is > > necessary to change the value of that variable in the control value > > program. Changes made in the control value program will apply to all > > subsequently processed glyphs unless INSTCTRL[] is used to inhibit > > these new values. You are looking at the outdated Apple's specifications. Please check with OpenType 1.9 instead: https://learn.microsoft.com/en-us/typography/opentype/spec/tt_instructions#instruction-execution-control
Specifically, "INSTCTRL[ ] can only be executed in the CVT program." There are further clarifications https://learn.microsoft.com/en-us/typography/cleartype/truetypecleartype#instctrl Best, Alexei
