Re: Pango crossplatform layout size query

[Richard Procter <richard n procter gmail com>]

On 9/04/2010, at 4:49 AM, Behdad Esfahbod wrote:

> On 04/06/2010 08:09 PM, Richard Procter wrote:
> > However, the cairo documentation states "hinting font metrics means
> > quantizing them so that they are integer values in  
> > devicbehdad behdad orge space". This
> > suggests I'm wrong and that layout remains device dependent.
>
> ??  If you *disable* hinting font metrics, you are supposed to get
> device-independent layout.

Right, that's what I thought.

"quantizing ... so that they are integer values in device space" though
suggests otherwise to me; I will go bug the cairo guys.

> > I have tested this using the attached C program on OS X 10.4,
> > Debian Linux (lenny), and Win32, using the same MS arial.ttf font  
> > file.
> > OS X and Linux get identical logical extents, but win32 differs (see
> > below for details - in fact it doesn't appear to honour the option).
>
> IIRC neither win32 nor quartz cairo font backends respect the  
> hinting flags
> (yet).  That's a bug.

It looks like quartz has been fixed - it matches linux with metrics
hinting off and differs with it on.

I will raise a bug for the win32 backend if there isn't one already.

> > If I understand metrics hinting, this last is a bug, and I can rely
> > on the others to remain equal, plus or minus a pixel? If so, can
> > I expect this to hold for other scripts?
>
> Yes.  The script is not relevant.

Great. I take it that I am basically on the right track then and that
when you said cross-platform results without metrics hinting were
'fairly robust' you were thinking of that single device pixel.

many thanks,
Richard.