🚀 go-pugleaf

The Postscript "clippath" verb makes the current path into a copy of the
current clipping path.  The "pathforall" verb walks the current path calling
one of four routines you supply.  There is one called for "move", one for
"line", one for "curve", and one for "close".  These routines can build a
data structure which you can then pull later.

I have seen this technique used to build a procedure body on the stack that
when later bound to a name and called restores the clipping path to that which
was in effect when the technique was used.  This is in Apple's laserwriter
prologue from printing 5.2 (prologue level 68).  If you can get a Macintosh
command-K dump you could probably extract much of the code from that.  Look
in the "od" procedure, which seems to bind the name "gc" to the enumerated
path (the transform-itransform is snapping to integer device coordinates).

N.B. This technique is deliberately and specifically DISallowed when the
outline of an Adobe character is in the clipping path.  This is to prevent
you from stealing the Adobe fonts...
-- 
Ben Cranston <zben@umd2.UMD.EDU>    (Kingdom of Merryland UniSys 1100/92)
Copyright 1989 (you may redistribute ONLY if your recipients can).