From: Andrew Dunbar (hippietrail@yahoo.com)
Date: Fri Aug 09 2002 - 02:22:39 EDT
--- Martin Sevior <msevior@physics.unimelb.edu.au>
wrote: > On Thu, 2002-08-08 at 23:55, Tomas Frydrych
wrote:
> >
> > I feel very strongly that before we start even
> putting out betas for
> > version 2 we have to get rid of the screen/layout
> units dichotomy.
> > The fact that we do some layout calculations in
> screen units and
> > some layout calculations in layout units, coupled
> with the way we
> > scale font metrics from one to the other, is
> responsible for probably
> > over 90% of our wysiwyg bugs. We have been trying
> hard to fix
> > many of these for long time, and we are just
> running in circles.
> >
> > The paradox of it all is that, AFAIK, there is no
> real reason why we
> > would need both sets of units and at places we
> just shamelessly
> > scale from one to the other.
> >
> > What I am proposing is that we remove both sets of
> units and
> > replace them with a single unit system identical
> to the one used by
> > Pango, where there are 1024 units to a screen
> pixel. This makes it
> > possible to quickly translate the internal units
> to screen units and
> > vice versa using shifts, and would provide us with
> a precision rougly
> > 15 times greater than our layout units do. It
> would also make the
> > eventual transition to Pango simpler.
> >
> > This would also result in a substantial
> performance improvement, for
> > measuring character widths is one of the
> bottlenecks and having
> > single set of units would reduce the processing to
> half.
> >
> > Now, if anyone has a good reason for keeping to
> coordinate
> > systems, then please speak up now.
> >
>
> HI Tomas,
> I haven't followed what you and Joaquin have been
> doing closely enough
> I guess. The last time I looked we needed to use
> widths from screen
> coordinates obtained directly from the on-screen
> glyph sizes to do
> horizontal text layout. We couldn't scale from high
> resolution printing
> sized glyphs to the screen resolution glyph becaus
> of hinting info at
> low resolution.
>
> Has this been fixed now? Where do we currently use
> high resolution glyph
> sizes to calculate screen layout?
I'm not the expert on this but isn it at all related
to
the fact that Xft actually renders at a higher
resolution into subpixels for the antialiasing, and
doesn't actually use any low-level hinting?
I guess it's probably not at least in the cross-
platform case. But can we take advantage of this
fact?
Andrew Dunbar.
> If this problem is solved I would love to get rid of
> the
> screen/layout/pango sized calculations and just go
> with pango units.
>
> Cheers
>
> Martin
>
>
=====
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