Re: [xmlroff] Re: xmlroff on Windows

[Tony G. <Ton...@Su...>]

Jesper Stigberg wrote at 30 Apr 2003 14:01:55 +0200:
 > Tony Graham wrote:
...
 > I think that this is the problem. From:
 > http://developer.gnome.org/doc/API/2.0/pango/pango-Glyph-Storage.html#PangoGlyphUnit
 > 
 > "...The PangoGlyphUnit type is used to store dimensions within
 > Pango. Dimensions are stored in 1/PANGO_SCALE of a device unit. (A
 > device unit might be a pixel for screen display, or a point on a
 > printer.)..."
 > 
 > note the "...(A device unit might be a pixel for screen display, or
 > a point on a printer.)..." i.e. a 'device-unit' may be a pt, but it
 > does not have to.

But a device unit is a point for font sizes:

   There are PANGO_SCALE Pango units in one device unit (device unit
   is a point, for font sizes).

(See http://developer.gnome.org/doc/API/2.0/pango/pango-Fonts.html#pango-font-description-set-size)

...
 > If the pango version in use uses pt as 'device-unit', all is
 > fine. But if it uses another unit we have a mix of units.

Which is why so far it has been fine, and why it creates problems for
your screen rendering backend.

I have started a Wiki page to collect in one place all the possibly
differing interpretations of device units from XSL, Pango, and
FreeType (although I haven't got to FreeType yet).  You are welcome to
annotate it.

What do you do in your rendering application if you want to scale the
rendered image, e.g. reduce it so a whole page appears in the window?

...
 > > Also, the XSL Recommendation errata says that 1 px = 1/96 inch.

Actually, it's a CSS2 erratum
(http://www.w3.org/Style/css2-updates/REC-CSS2-19980512-errata.html),
and the XSL 1.0 erratum removes the size recommendation from the XSL
1.0 Recommendation (so XSL won't be bothered by any future dpi changes
in CSS).

 > Note that in fo-expr-eval.c pt==px.
 > 
 > #define POINT2DEVICE(x)		x
 > #define PIXEL2DEVICE(x)		x
 > 
 > Do you want me to file a bug?

Sure.  Note also that the code for fo:external-graphic has wavered
about the dpi.

Regards,


Tony Graham
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