Fontconfig - Aug 2008 - Forcing Artificial Italics on Fonts That *DO* Have One Available?

I understand that this bit of code in .fonts.conf will enable italics 
for fonts that do not have an italic face available:


    <!-- Artificial oblique for fonts without an italic or oblique 
version -->
    <match target="font" >
        <!-- check to see if the font is roman -->
        <test name="slant" >
            <const>roman</const>
        </test>
        <!-- check to see if the pattern requested non-roman -->
        <test target="pattern" compare="not_eq"
name="slant" >
            <const>roman</const>
        </test>
        <!-- multiply the matrix to slant the font -->
        <edit mode="assign" name="matrix" >
            <times>
                <name>matrix</name>
                <matrix>
                    <double>1</double>
                    <double>0.2</double>
                    <double>0</double>
                    <double>1</double>
                </matrix>
            </times>
        </edit>
        <!-- pretend the font is oblique now -->
        <edit mode="assign" name="slant" >
            <const>oblique</const>
        </edit>
    </match>


I am interested in *forcing* this behavior on fonts that *do* have an 
italic face available, because I like the way the artificial rendering 
looks.  I have been unable to make it work however. It seems that once 
an existing italic font has been selected, fontconfig will not give it 
up.  One of my approaches was to have a piece of XML prior to the above 
which "undoes" any existing italic:

    <!-- Artificial oblique for fonts WITH an italic or oblique version
-->
    <match target="font" >
        <!-- check to see if the font is NOT roman -->
        <test name="slant" compare="not_eq">
            <const>roman</const>
        </test>
        <!-- check to see if the pattern requested non-roman -->
        <test target="pattern" compare="not_eq"
name="slant" >
            <const>roman</const>
        </test>
        <edit mode="append" binding="same"
name="slant">
            <const>roman</const>
        </edit>
    </match>

But, the end effect is to do double italics, i.e. it slants it twice.  
Does anybody have an idea on how to force it to first select the regular 
font, then apply artificial slanting to it?

Thanks,
Erik

On Mon, 2008-08-04 at 20:06 -0500, Erik wrote:
> 
> But, the end effect is to do double italics, i.e. it slants it twice.  
This is because the italic face has already been selected.
> Does anybody have an idea on how to force it to first select the regular 
> font, then apply artificial slanting to it?
I have a couple of ideas:

  - Ban all Italic fonts so fontconfig does not see them at all. (may
use target=scan for this, not sure).

  - This one should be easier:

    * In target=pattern, copy the slant value to a temp variable (say,
saved_slant),
    * In target=pattern reset slant to roman,
    * In target=font, use saved_slant to decide whether to do artificial
slanting.

HTH,

-- 
behdad
http://behdad.org/

"Those who would give up Essential Liberty to purchase a little
 Temporary Safety, deserve neither Liberty nor Safety."
        -- Benjamin Franklin, 1759

On Tue, Aug 5, 2008 at 7:22 AM, Behdad Esfahbod <behdad at behdad.org>
wrote:
>
> I have a couple of ideas:
>
>  - Ban all Italic fonts so fontconfig does not see them at all. (may
> use target=scan for this, not sure).
This one is bad. Fonts have italic versions for a reason: some have
different glyph shapes, which aren''t simply oblique versions of the
regular upright font. Also, some fonts like Latin Modern Serif even
have an upright italic version.
>  - This one should be easier:
>
>    * In target=pattern, copy the slant value to a temp variable (say,
> saved_slant),
>    * In target=pattern reset slant to roman,
>    * In target=font, use saved_slant to decide whether to do artificial
> slanting.
>
> HTH,
>
> --
> behdad
> http://behdad.org/
>
> "Those who would give up Essential Liberty to purchase a little
>  Temporary Safety, deserve neither Liberty nor Safety."
>        -- Benjamin Franklin, 1759
>
> _______________________________________________
> Fontconfig mailing list
> Fontconfig at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/fontconfig
>
>

On Tue, 2008-08-05 at 08:39 +0300, Vasile Gaburici
wrote:
> 
> On Tue, Aug 5, 2008 at 7:22 AM, Behdad Esfahbod <behdad at
behdad.org>
> wrote:
> >
> > I have a couple of ideas:
> >
> >  - Ban all Italic fonts so fontconfig does not see them at all. (may
> > use target=scan for this, not sure).
> 
> This one is bad. Fonts have italic versions for a reason: some have
> different glyph shapes, which aren''t simply oblique versions of
the
> regular upright font. Also, some fonts like Latin Modern Serif even
> have an upright italic version.
If a user wants to configure his fontconfig to do that, why do *you*
care?

-- 
behdad
http://behdad.org/

"Those who would give up Essential Liberty to purchase a little
 Temporary Safety, deserve neither Liberty nor Safety."
        -- Benjamin Franklin, 1759

On Mon, 2008-08-04 at 20:06 -0500, Erik wrote:
> Does anybody have an idea on how to force it to first select the regular 
> font, then apply artificial slanting to it?
Not to condone this kind of typographical abuse, but it seemed an
interesting problem. The key is to switch to a roman font for the match,
but then patch up the returned roman font to perform the artificial
oblique effect. I think fontconfig provides too much flexibility some
days.

<match target="pattern">

        <!-- match requests for non-roman face -->
        <test name="slant" compare="not_eq">
                <const>roman</const>
        </test>

        <!-- remember that this should be slanted -->
        <edit name="fake_slant">
                <bool>true</bool>
        </edit>

        <!--- change to match a roman face instead -->
        <edit name="slant">
                <const>roman</const>
        </edit>
</match>

<match target="font">

        <!-- check to see if the font is roman -->
        <test name="slant">
                <const>roman</const>
        </test>

        <!-- look for fonts which were marked for fake obliquing -->
        <test name="fake_slant">
                 <bool>true</bool>
        </test>

        <!-- multiply the matrix to slant the font -->
        <edit name="matrix" mode="assign">
                <times>
                        <name>matrix</name>
                               
<matrix><double>1</double><double>0.2</double>
                                       
<double>0</double><double>1</double>
                                </matrix>
                </times>
        </edit>

        <!-- mark the font as oblique now -->
        <edit name="slant">
                <const>oblique</const>
        </edit>
</match>

-- 
keith.packard at intel.com
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If it makes you guys feel any better, I didn''t actually want this for 
every italic font, just those that I am doing BCI full hinting on 
(mainly MS ones).  Otherwise the stems on letters look like a field of 
grass waving in the wind.  So, I''m simply doing glyph abuse to fix
glyph
abuse!

After posting, I played around a bit more and got the below code to 
work, but I wasn''t able to figure out how to insert multiple fonts 
within this code; it had to be duplicated for every font.  Keith''s 
solution is more elegant and lets me put multiple fonts in the code.  
Thanks for the help!


    <selectfont>
        <rejectfont>
            <pattern>
                <patelt name="family" >
                    <string>Courier New</string>
                </patelt>
                <patelt name="slant" >
                    <const>italic</const>
                </patelt>
            </pattern>
        </rejectfont>
    </selectfont>