🚀 go-pugleaf

% Hello all!

% I hope I don't bother you with an frequently asked question, but I'm a
beginner
% in postscript and I can't find the (maybe simple?) solution to the problem in
% the handbooks I have access to.

% All I want is a text printed in the center of a box!
% I included a fragment of my program, just to illustrate the problem:
% 'Box' and 'CenterShow' work fine and the text is left/right centered.
% Obviously the problem is the font height!
% When I calculated the y-coordinate I started with 'y-start + half-box-height'
% and the text showed above the middle. So I substracted 'half-font-height',
% but now the small letters 'g' and 'j' are partially outside the box!

% My question now is threefold:
% a. Why is the starting point of a letter not the lower left corner of the
%    matrix?
% b. How can I calculate the right 'offset' when I know the font height?
% c. It appears to me as if the font height 50 is not equal to my definition
%    of the box height 50 ?? Why is that so?

% Thanks a lot for any help!
%                              Willi


%!

/Box {                                 %---------------------------------------
  4 2 roll                             % draw a box
  newpath                              % stack:  x-start y-start width height
    moveto                             %---------------------------------------
    dup 0 exch rlineto
    exch 0 rlineto
    neg 0 exch rlineto
  closepath
} def

/CenterShow {                          %---------------------------------------
  dup                                  % print a string centered
  stringwidth pop 2 div neg            %---------------------------------------
  0 rmoveto
  show
} def

/x 100 def                 % lower left corner of box
/y 100 def
/w 200 def                 % width of box
/h  50 def                 % height of box
/f  50 def                 % font height

/Helvetica findfont f scalefont setfont

x y w h Box stroke         % print the box

x w 2 div add              % x-start + half-box-width
y h 2 div add f 2 div sub  % y-start + half-box-height - half-font-height
moveto

(Agthijkl) CenterShow      % show arbitrary text
showpage

%  <>==============================<>=============================<>========<>
%  || Wilhelm F.Staudt             || E-Mail:                     ||  \     ||
%  || Department of Physics        ||                             ||   \    ||
%  || University of Kaiserslautern || staudt@physik.uni-kl.de     ||   /\   ||
%  || FRG - 6750 Kaiserslautern    || staudt@rhrk.uni-kl.de       ||  /  \  ||
%  <>==============================<>=============================<>========<>