Re: TrueType & Fontname

[Werner LEMBERG <sx0005@sx2.hrz.uni-dortmund.de>]

   >Well, at least the FreeType rastering engine offers both
   >non-linearly scaled metrics (as automatically given if hinting is
   >activated) for display on screens and linearly scaled metrics for
   >typesetting purposes.  I doubt that the problem of non-linear
   >scaling is relevant for TeX issues at all, since most printers
   >work at resolutions where hinting is deactivated resp. without
   >influence.

   Are we talking about the same thing (we may very well be, I am just
   asking).  I am not talking about adjustements to the glyphs via
   hinting.  I am talking about adjustments to the metrics of the font
   (advance width) based on grid fitting to a finite grid.  An
   unusually bad idea in my opinion.

You are mixing up two rather unrelated purposes of TrueType fonts.
The first purpose is to serve as a font for screen display (usually
done with bitmap glyphs on other OSes), and the second is the
classical use for typography.

TrueType fonts can contain two sets of metrics (and even four if the
font is intended for vertical writing also).  The `hdmx' table
(Horizontal Device Metrics), the `hmtx' table (Horizontal Metrics),
and the vertical pendants.

If you use the font for screen display, e.g., to show a system message
in a pop-up window or to support a web browser, you have different
sets of device metrics for assorted ppem values in the hdmx table --
better TT fonts like arial for Windows contain a lot of hinting
instructions to make the font outline appear pleasing at such low
resolutions.  And to do that properly, you have to modify advance
widths even within the glyph itself.  Note that not all fonts have a
hdmx table since it is optional.  Usually, a missing hdmx table
indicates that this font is not to be used for screen display and will
render badly at extremely low ppem values.

So non-linearly scaled metrics are useful, but not for typography of
course.

On the other hand, the hmtx table always give linearly scaled metrics
for typographical purposes, and this is what word processors will use.

   E.g. if I send you a file in Word say (heaven forbid) and you look
   at it on your screen you will get different line and page breaks if
   your screen resolution is not the same.

This won't happen for the reasons outlined above.


    Werner