Perhaps let me ask the opposite question: do you really expect setting 
projection vector and rp1 in prep to have global effects on every glyph, and/or 
setting those in one glyph to have effect on another glyph?
In fact, those are per contour / contour fragment values.
Today's Topics:

  1. FreeType INSTCTRL behavior (Po Lu)


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Message: 1
Date: Sun, 12 Feb 2023 23:40:09 +0800
From: Po Lu <[email protected]>
To: [email protected]
Subject: FreeType INSTCTRL behavior
Message-ID: <[email protected]>
Content-Type: text/plain

As part of the Android port [of GNU Emacs], I've been writing a module
to display TrueType fonts.  This includes a TrueType interpreter for
instructing fonts.

  (Please don't ask why I'm not just using FreeType.  Building
  dependencies for Android is not easy.)

AFAIU, as long as a font does not perform an INSTCTRL which sets bit 2
in the instruction control, changes made to the graphics state from the
control value program will become the ``default'' state from which
glyphs are instructed.

However, some CJK fonts perform no INSTCTRL instructions at all, change
the projection vector and rp1 from prep, yet FreeType resets both to the
X axis and 0 respectively before any glyph programs are run.

Am I missing anything?  If not, could anyone here tell me where this
behavior is documented?

Thanks.

  

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