Re: [xmlroff] Re: xmlroff on Windows

[Jesper S. <je...@no...>]

Tony Graham wrote:
> Jesper Stigberg wrote at 30 Apr 2003 14:01:55 +0200:
>  > Tony Graham wrote:
> 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)

Yes.

> ..
>  > 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.
> 

Yup.

> 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.

Great. What do gnome-print use as a unit?

> 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?
> 

A bit simplified.

In the win32 GDI (graphics device interface), all drawing, text-output etc is 
done through a device-context using logical-units. What appears on the screen is 
measured in device-units. A device-unit==scale*logical-unit ( this mapping is 
done by the OS ). So by changing the scale you can get a zoom effect without 
changing the coordinates etc in your drawing code, or use the same code to 
render to a printer.

> ..
>  > > 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.

Noted.

Regards,
Jesper.