Subject: Re: Systematic error on display versus layout units.
From: Thomas Fletcher (thomasf@qnx.com)
Date: Thu Jun 28 2001 - 15:22:23 CDT
On Fri, 29 Jun 2001, Martin Sevior wrote:
> On Thu, 28 Jun 2001, Martin Sevior wrote:
>
> > Hi Folks,
> > I've spent the last couple of days fighting with 1632. Basically
> > our text in left justified mode can easily extend way past the right
> > margin.
> >
> > This is caused by a systematic errors between font sizes at screen
> > resolution and font sizes at Layout resolution. Relative to the screen
> > resolution, the layout resolution of the Type 1 fonts that ship with Abi
> > are smaller by a few %.
> >
>
> I know the problem now:-) The calculation of the correct font is current
> getting the closest size font to that need at poor resolution, then again
> at high resolution. The poor resolution font can be wrong by 1 units out
> of about 25 for 12 point fonts. This leads to a few percent error due to
> rounding at poor resolution (about 1 unit out of 25) so that that's about
> 4 %.
>
> The way to deal with this is to scale the font chosen at poor resolution
> so that the high resolution font is the best match possible to poor
> resolution Font.
>
> I believe that something like this may responsible for the non-WYSIWYG
> reformance of gnome-print. I'll look and see anyway.
Just to let you know ... I get the same behavioural problems
here with there not being a linear scale in metrics between
what we use for calculations and the on screen size. This
work was done a long time ago to get around floating point
precision usage so that all metrics were done at a "higher"
scale. Personally I would just have gone to floating point
since we take a big performance hit having to ask twice for
every character/point size.
Thomas
-------------------------------------------------------------
Thomas (toe-mah) Fletcher QNX Software Systems
thomasf@qnx.com Neutrino Development Group
(613)-591-0931 http://www.qnx.com/~thomasf
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