copyfont and font features

copyfont and font features

[Ulrike Fischer]

This comes from a tex.sx question
https://tex.stackexchange.com/questions/338942/cancellation-of-color-fontspec-font-settings-while-defining-microtype-context/

The primitive \copyfont looses with open type fonts all font
features:

\starttext

\font\testa={Arial:mode=node;script=latn;language=DFLT;+tlig;+smcp;}
{\testa abc -- }  normal

\copyfont\testb\testa

{\testb abc -- } normal

\stoptext

As one can see \testb has neither ligatures nor it is in small caps.
Is this a bug or to be expected?

If the second: Is there in the fontloader a replacement which can be
used to copy fonts?


-- 
Ulrike Fischer 
http://www.troubleshooting-tex.de/

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Re: copyfont and font features

[Hans Hagen]

On 11/16/2016 6:17 PM, Ulrike Fischer wrote:
> This comes from a tex.sx question
> https://tex.stackexchange.com/questions/338942/cancellation-of-color-fontspec-font-settings-while-defining-microtype-context/
>
> The primitive \copyfont looses with open type fonts all font
> features:
>
> \starttext
>
> \font\testa={Arial:mode=node;script=latn;language=DFLT;+tlig;+smcp;}
> {\testa abc -- }  normal
>
> \copyfont\testb\testa
>
> {\testb abc -- } normal
>
> \stoptext
>
> As one can see \testb has neither ligatures nor it is in small caps.
> Is this a bug or to be expected?

It's to be expected as \copyfont makes a copy at the tfm level. One can 
just use

\let\testb\testa

instead. Information related to fonts at the lua end is not known to 
\copyfont.

> If the second: Is there in the fontloader a replacement which can be
> used to copy fonts?

I think the \copyfont primitive was introduced in pdftex as a kind of 
speedup (not that there was any speed to gain) or convenience (saves a 
define) for applying protrusion and other tricks (luatex dropped most of 
them) to a font. So, the primitive is only there for compatibility reasons.

It makes no sense to have a replacement (at least I can't think of a 
case that can't be handled already). Just define the font again.

Hans

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                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
        tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
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Re: copyfont and font features

[Ulrike Fischer]

Am Thu, 17 Nov 2016 09:46:26 +0100 schrieb Hans Hagen:

> On 11/16/2016 6:17 PM, Ulrike Fischer wrote:
>> This comes from a tex.sx question
>> https://tex.stackexchange.com/questions/338942/cancellation-of-color-fontspec-font-settings-while-defining-microtype-context/
>>
>> The primitive \copyfont looses with open type fonts all font
>> features:
>>
>> \starttext
>>
>> \font\testa={Arial:mode=node;script=latn;language=DFLT;+tlig;+smcp;}
>> {\testa abc -- }  normal
>>
>> \copyfont\testb\testa
>>
>> {\testb abc -- } normal
>>
>> \stoptext
>>
>> As one can see \testb has neither ligatures nor it is in small caps.
>> Is this a bug or to be expected?
 
> It's to be expected as \copyfont makes a copy at the tfm level. One can 
> just use
> 
> \let\testb\testa
> 
> instead. 

Simply using \let doesn't work when you want locally a different
expansion behaviour:

   ! error:  (font expansion): font has been expanded with different
stretch limit. 

(with pdflatex + lualatex), that's imho the reason why microtype
copies the fonts. 


> It makes no sense to have a replacement (at least I can't think of a 
> case that can't be handled already). Just define the font again.

The question is if microtype can easily retrieve the current font
features and if it will slow down the code much if it has to
redefine fonts again and again. 


-- 
Ulrike Fischer 
http://www.troubleshooting-tex.de/

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Re: copyfont and font features

[Hans Hagen]

On 11/17/2016 11:02 AM, Ulrike Fischer wrote:
> Am Thu, 17 Nov 2016 09:46:26 +0100 schrieb Hans Hagen:
>
>> On 11/16/2016 6:17 PM, Ulrike Fischer wrote:
>>> This comes from a tex.sx question
>>> https://tex.stackexchange.com/questions/338942/cancellation-of-color-fontspec-font-settings-while-defining-microtype-context/
>>>
>>> The primitive \copyfont looses with open type fonts all font
>>> features:
>>>
>>> \starttext
>>>
>>> \font\testa={Arial:mode=node;script=latn;language=DFLT;+tlig;+smcp;}
>>> {\testa abc -- }  normal
>>>
>>> \copyfont\testb\testa
>>>
>>> {\testb abc -- } normal
>>>
>>> \stoptext
>>>
>>> As one can see \testb has neither ligatures nor it is in small caps.
>>> Is this a bug or to be expected?
>
>> It's to be expected as \copyfont makes a copy at the tfm level. One can
>> just use
>>
>> \let\testb\testa
>>
>> instead.
>
> Simply using \let doesn't work when you want locally a different
> expansion behaviour:
>
>    ! error:  (font expansion): font has been expanded with different
> stretch limit.
>
> (with pdflatex + lualatex), that's imho the reason why microtype
> copies the fonts.

in fact that is also the case with pdftex: afaik expansion and 
protrusion values are global and once a font is used they get frozen

in luatex (at least the lua font loader) one can set the expansion at 
definition time (which is more natural but not possible in pdftex)

>> It makes no sense to have a replacement (at least I can't think of a
>> case that can't be handled already). Just define the font again.
>
> The question is if microtype can easily retrieve the current font
> features and if it will slow down the code much if it has to
> redefine fonts again and again.

that's a matter of implementation

(because expansion slows down processing anyway, defining an extra font 
is hardly the bottleneck - just some milliseconds)

Hans


-----------------------------------------------------------------
                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
        tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
-----------------------------------------------------------------
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___________________________________________________________________________________

Re: copyfont and font features

[Ulrike Fischer]

Am Thu, 17 Nov 2016 13:07:22 +0100 schrieb Hans Hagen:

>> Simply using \let doesn't work when you want locally a different
>> expansion behaviour:
>>
>>    ! error:  (font expansion): font has been expanded with different
>> stretch limit.
>>
>> (with pdflatex + lualatex), that's imho the reason why microtype
>> copies the fonts.
> 
> in fact that is also the case with pdftex: afaik expansion and 
> protrusion values are global and once a font is used they get frozen

Yes, exactly. 

> 
> in luatex (at least the lua font loader) one can set the expansion at 
> definition time (which is more natural but not possible in pdftex)

Yes, but I understand that -- if possible -- microtype prefers code
that works in pdftex *and* luatex.  


>> The question is if microtype can easily retrieve the current font
>> features and if it will slow down the code much if it has to
>> redefine fonts again and again.
 
> that's a matter of implementation

Yes, the maintainer of microtype has been informed about the problem
and can now look for a solution ...



-- 
Ulrike Fischer 
http://www.troubleshooting-tex.de/

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