Re: FreeType INSTCTRL behavior (Po Lu) (Re: Freetype-devel Digest, Vol 217, Issue 8)

[Alexei Podtelezhnikov]

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You are looking at the outdated Apple's specifications.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