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the interaction of gsave/grestore and save/restore
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luser- -droog
Nov 30, 2013, 11:32:04 PM11/30/13
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Understanding this part of postscript has taken me a rather
long time, so I present a rant and ramble about "what's the diff?"
The graphics state is an object in local VM.
gsave and grestore implement some kind of stack at the ps-level
which creates copies and makes redefinitions to manage a graphics
stack as a postscript abstract data type (probably an array and
index pair defined in a dictionary).
Arrays and Dicts are VM objects.
Therefore save and restore which operate on VM as a whole,
naturally produce the desired effects upon the VM structures that
comprise the graphics state data structure, without any special-cases.
Because it's built out of arrays and dicts, and all arrays and dicts
get reverted by restore.
long time, so I present a rant and ramble about "what's the diff?"
The graphics state is an object in local VM.
gsave and grestore implement some kind of stack at the ps-level
which creates copies and makes redefinitions to manage a graphics
stack as a postscript abstract data type (probably an array and
index pair defined in a dictionary).
Arrays and Dicts are VM objects.
Therefore save and restore which operate on VM as a whole,
naturally produce the desired effects upon the VM structures that
comprise the graphics state data structure, without any special-cases.
Because it's built out of arrays and dicts, and all arrays and dicts
get reverted by restore.
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