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From: lee@leo (Bill Lee)
Newsgroups: comp.lang.postscript
Subject: Re: 0 0 moveto (+) show: how to center the (+)?
Message-ID: <1991Jun7.141203.14783@shell.shell.com>
Date: 7 Jun 91 14:12:03 GMT
References: <9106020627.AA01346@einstein.physics.buffalo.edu> <1991Jun3.084911.20213@cs.nott.ac.uk> <78801@eerie.acsu.Buffalo.EDU>
Sender: usenet@shell.shell.com (USENET News System)
Organization: Shell Oil
Lines: 74

In article <78801@eerie.acsu.Buffalo.EDU> xiaofei@acsu.buffalo.edu (X. F. Wang) writes:
>/* swx@cs.nott.ac.uk (Stephen Woolston) wrote */:
>* In article <9106020627.AA01346@einstein.physics.buffalo.edu>
>* xiaofei@EINSTEIN.PHYSICS.BUFFALO.EDU (X. F. Wang) writes:
>* >I need something
>* >
>* >x y moveto 
>* >( symbol ) show
>* >
>* >in drawing agraph. The probem is the symbol is not centered at
>* >currentpoint [The lower left corner is at currentpoint]. How do I
>* >symbol centered at currentpoint ?
>* 
>* Haven't tried it, but off the top of my head ...
>* 
>* 	x y moveto
>* 	(symbol) dup	% stack[ (symbol) (symbol) ]
>* 	stringwidth	% stack[ (symbol) xwid ywid ]
>* 	2 div neg	% stack[ (symbol) xwid -ywid/2 ]
>* 	exch		% stack[ (symbol) -ywid/2 xwid ]
>* 	2 div neg	% stack[ (symbol) -ywid/2 -xwid/2 ]
>* 	exch		% stack[ (symbol) -xwid/2 -ywid/2 ]
>* 	rmoveto show	% stack[ ]
>* 
>* You might like to define {dup ... show} as a procedure.
>
>Believe it or not, ywid is always 0. So (symbol) does not get vertically
>centered. If it is (symbol), one can use charpath flattenpath pathbox
>to get (symbol) vertically centered. However if it is a (string),
>I pick up a letter, say (M), to calculate the height. But this is not a
>perfect way of doing things. (abc) and (XYZ) do not have the same size
>as (M). So the question is how to calculate (AbiTaRy) string height as
>this? Or how to center an (aBItArY) string like this *vertically* ?
>-- 
>         (___) |              Xiaofei Wang                   | (___)
>         (o o) |   Physics Department / 239 Fronczak Hall    | (o o)
>  /-------\ /  |   State University of New York at {Buffalo} |  \ /-------\
> / |     ||O   |        {Buffalo}, New York 14260            |   O||     | \




Here is a procedure that does what you want. The only caveat is that the 
flattenpath operator when working on a long character string may get a
limit check if the string is too "verbose".

Bill Lee			lee@shell.com
Shell Oil Co.

------------------------------cut here---------------------------------------
%*___________________________ CenterChar _______________________________________
%* Procedure to reposition the currentpoint so that the input character string
%* will be centered both horizontally and vertically at the current point.
%*
%*	Usage: string CenterChar string
%*
%*
/CenterChar {
  dup
  gsave
    true charpath flattenpath
    pathbbox    	% llx lly urx ury
  grestore 
  exch			% llx lly ury urx
  3 1 roll		% llx urx lly ury
  add 2 div		% llx urx CenterY
  3 1 roll		% CenterY llx urx
  add 2 div		% CenterY CenterX
  currentpoint		% CenterY CenterX cx cy
  3 1 roll		% CenterY cy CenterX cx
  sub neg		% CenterY cy MoveX
  3 1 roll sub neg	% MoveX MoveY
  rmoveto
} def