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Re: font substitution


From: Yen-Ju Chen
Subject: Re: font substitution
Date: Fri, 10 Aug 2007 17:30:30 -0700

O.K. Sorry for another reply
This patch fixes the upside-down problem.
The attached screenshot uses English font as default font
and Chinese font as substitute.
I probably need to find a Japanese font and a symbol font to test
multiple substitute.
By the way, the speed is not bad.
Previously I said that it takes 1-2 seconds for 25,000+ Chinese glyphs
is including putting all glyphs on a NSMatrix.
So it is fast to get the coverage in NSFont.

Yen-Ju

On 8/10/07, Yen-Ju Chen <address@hidden> wrote:
> Another issue is that sometimes freetype fails to get the coverage.
> Therefore, NSCharacterSet raise an exception:
> "Specified range exceeds character set".
> So this patch prevents NSAttributedString from using all available fonts
> to eliminate the possibility of using bad fonts.
> It only uses user specified fonts for substitution.
> And I hope GNUstep can add an user default to specify the preferred fonts.
>
> Once the patch is applied, the font substitute basically works, but
> has one problem.
> I attach a screenshot to explain that.
> The left window is using English font as default font and no preferred font.
> So you only see English 'GNUstep'.
> The middle window is using Chinese font as default font and no preferred font.
> Because Chinese font also contains English letter,
> you see both English and Chinese.
> You can tell the English letter is from different font.
> The right window is using English font as default font and Chinese
> font as substitute.
> Again, you can see both English and Chinese character.
> But the funny thing is the Chinese character is upside-down.
> I have no idea why it happens, but I suspect gui or back cache the font matrix
> so the matrix of English font is applied to the Chinese font.
> The hint of Chinese font is also different between middle and right window.
> The middle one is sharp while the right one is blur.
> It indicates something is cached, probably for the English font at the
> start of the text.
> Maybe someone has insights about what may cause it.
>
> Yen-Ju
>
> On 8/10/07, Yen-Ju Chen <address@hidden> wrote:
> > Hi,
> >
> >   [NSFont coveredCharacterSet] is broken.
> >   I attach a patch.
> >   A quick test shows that a Chinese font which contains 25,000+ glyph
> >   takes only about 1-2 seconds to go through.
> >   It's on a powerbook G4 1GHz.
> >   So cache may not be needed for coveredCharacterSet.
> >   I haven't test the preferredFont yet.
> >   Hope this patch can go in soon.
> >
> >   Yen-Ju
> >
> > On 8/9/07, Yen-Ju Chen <address@hidden> wrote:
> > > On 8/9/07, Fred Kiefer <address@hidden> wrote:
> > > > Yen-Ju Chen wrote:
> > > > > On 8/8/07, Fred Kiefer <address@hidden> wrote:
> > > > >> Yen-Ju Chen wrote:
> > > > >>>   Another thing I am thinking is to save the coveredCharacterSet on 
> > > > >>> disk.
> > > > >>>   Font does not change frequently,
> > > > >>>   and it does take time to generate coveredCharacterSet for each 
> > > > >>> font,
> > > > >>>   especially for CJK.
> > > > >>>   If the cached coveredCharacterSet can be saved on disk and loaded 
> > > > >>> later,
> > > > >>>   it can reduce the overhead of starting an application.
> > > > >>>   For art backend, it can even pack the saved coveredCharacterSet 
> > > > >>> in nfont.
> > > > >>>   So for small font, it is fine to check the covered character each 
> > > > >>> time.
> > > > >>>   For big font, saved character set is better.
> > > > >>>
> > > > >> Great idea! Would you like to work on that?
> > > > >
> > > > >   If the patch you have goes into the -trunk,
> > > > >   I can play with it and see how much it effects the speed
> > > > >   and decide what's the best way to do the cache if needed.
> > > > >
> > > >
> > > > I just committed this change, now it is your turn :-)
> > >
> > >   Thanx. I will take a look shortly.
> > >
> > >   Yen-Ju
> > >
> > > >
> > >
> >
> >
>
>

Attachment: gnu_attributedstring2.patch
Description: Text Data

Attachment: font_sub2.png
Description: PNG image


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