=========================================================================
Date:         Tue, 2 Apr 91 12:02:48 MSZ
Reply-To:     The TUG DVI driver standards discussion list
              <DRIV-L@TAMVM1.BITNET>
Sender:       The TUG DVI driver standards discussion list
              <DRIV-L@TAMVM1.BITNET>
From:         XITIJSCH@DDATHD21.BITNET
Subject:      Re: vertical kerning again
 
On the discussion about the TFM dimensions and the glyph dimensions:
 
 1. First of all, I see no problem to include a sentence in the standard
    to clarify the fact that glyphs may be outside of the ``TFM box.''
        Such a sentence does not destroy anything and warns new driver
    writers.
 
 2. A driver may not notice a ``TFM box'' after all because it does
    not read TFM files -- and the TFM height is not recorded in GF/PK
    files. So item (1) will be just a hint -- it should go into
    the explanations, not in the standards text.
        (In my personal opinion, reading TFM files is a waste of computing
    time, memory, and programming overhead. One simply doesn't need it.)
 
Shall I formulate something?
 
 
    Joachim
 
 
P.S.: Concerning the HP LaserJet: The bounding box is not used for
      memory management. In earlier firmware versions it was used for
the clipping algorithm, to decide if a character fits on the page.
Newer firmware versions (e.g., in the IIP and the III) don't use the
bounding box for clipping any more. If it is now used for anything is
unknown.
    Please note that the information above was derived by HP
documentation and a lot of experiments to fill in the holes in the
documentation. (We implemented a font caching in our HP driver and
needed the precise facts how the memory management works.)
 
P.P.S: If anybody has similar information on the HP DeskJet with
       downloaded fonts, please let me know...
 
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