decomposed and precomposde glyphs

decomposed and precomposde glyphs

[Ulrike Fischer]

When using input like the following with xetex then harfbuzz kicks
in and one would always get the good looking precomposed U+1EA0 for
the A and the decomposed B+U+0323 for the B.

With context (and lualatex) one get a rather bad looking -- as the
dot is misplaced -- output for the A^^^^0323 input and no output at
all for ^^^^1e04. 

As the coverage for precomposed glyphs varies a lot across fonts
this is rather a nuisance.  Is there a way to get the fontloader
(also the one used by luaotfload) to do a similar substituation as
done by harfbuzz?

\starttext
\catcode`\^= 7
Ạ A^^^^0323  %decomposed input -> U+1EA0 with xetex

Ạ  ^^^^1ea0  %precomposed input 


Ḅ B^^^^0323  %decomposed input

^^^^1e04     %precomposed input -> B+U+0323 with xetex


\stoptext


(I added the ^^-notation to avoid problems with copy&paste) 

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

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Re: decomposed and precomposde glyphs

[Hans Hagen]

On 2/23/2017 11:58 AM, Ulrike Fischer wrote:
> When using input like the following with xetex then harfbuzz kicks
> in and one would always get the good looking precomposed U+1EA0 for
> the A and the decomposed B+U+0323 for the B.
>
> With context (and lualatex) one get a rather bad looking -- as the
> dot is misplaced -- output for the A^^^^0323 input and no output at
> all for ^^^^1e04.
>
> As the coverage for precomposed glyphs varies a lot across fonts
> this is rather a nuisance.  Is there a way to get the fontloader
> (also the one used by luaotfload) to do a similar substituation as
> done by harfbuzz?
>
> \starttext
> \catcode`\^= 7
> Ạ A^^^^0323  %decomposed input -> U+1EA0 with xetex
>
> Ạ  ^^^^1ea0  %precomposed input
>
>
> Ḅ B^^^^0323  %decomposed input
>
> ^^^^1e04     %precomposed input -> B+U+0323 with xetex
>
>
> \stoptext
>
>
> (I added the ^^-notation to avoid problems with copy&paste)

In context one can enable a collapse (last week i found out that it was 
off by default).

Anyway, there are two issues here:

(1) one can in the input stream collapse the dot accent and the other 
character but of course an altered input might not be what one wants, 
for instance because fonts fonts not always provide a decompose (ccmp) 
or composed glyphs

(2) one can mess at the node list level which has a potyential drawback 
that one cannot get a character (explicit \char) there without the 
danger of it being mangled

so, whatever method one chooses, it has to be controlled because in tex 
all is about control (think of verbatim)

I have a file here that implements a pseudo feature that does this kind 
of (trivial) magic and I can add that to the distribution. (btw, I 
suppose that xetex can disable that on demand as from your post I deduce 
that it's default behaviour and fighting defaults is a pain).

Hans

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               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: decomposed and precomposde glyphs

[Ulrike Fischer]

Am Thu, 23 Feb 2017 13:19:12 +0100 schrieb Hans Hagen:

> On 2/23/2017 11:58 AM, Ulrike Fischer wrote:
>> When using input like the following with xetex then harfbuzz kicks
>> in and one would always get the good looking precomposed U+1EA0 for
>> the A and the decomposed B+U+0323 for the B.
>>
>> With context (and lualatex) one get a rather bad looking -- as the
>> dot is misplaced -- output for the A^^^^0323 input and no output at
>> all for ^^^^1e04.
>>
>> As the coverage for precomposed glyphs varies a lot across fonts
>> this is rather a nuisance.  Is there a way to get the fontloader
>> (also the one used by luaotfload) to do a similar substituation as
>> done by harfbuzz?
>>
>> \starttext
>> \catcode`\^= 7
>> Ạ A^^^^0323  %decomposed input -> U+1EA0 with xetex
>>
>> Ạ  ^^^^1ea0  %precomposed input
>>
>>
>> Ḅ B^^^^0323  %decomposed input
>>
>> ^^^^1e04     %precomposed input -> B+U+0323 with xetex
>>
>>
>> \stoptext
>>
>>
>> (I added the ^^-notation to avoid problems with copy&paste)
> 
> In context one can enable a collapse (last week i found out that it was 
> off by default).
> 
> Anyway, there are two issues here:
> 
> (1) one can in the input stream collapse the dot accent and the other 
> character but of course an altered input might not be what one wants,

No changing the input is imho not a solution as the document fonts
can have different coverage of the glyphs. Whatever is done must be
font dependant. 

> (btw, I suppose that xetex can disable that on demand as from your
> post I deduce that it's default behaviour and fighting defaults
> is a pain).

I don't think that one disable the behaviour in xetex, the internal
harfbuzz library is doing it. There is imho no way to get a
A+combining accent in a document.

I agree that it would be neat to be able to disable it but on the
whole: if I had only the choice between "the xetex-substituation"
and the current luatex/context behaviour I would prefer the first.
For normal documents it is preferable. 

Did you sent the second mail only for me for a reason or did you
only forget to add the list? Imho this is interesting for others
too. 


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

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Re: decomposed and precomposde glyphs

[Hans Hagen]

On 2/23/2017 1:35 PM, Ulrike Fischer wrote:

> Did you sent the second mail only for me for a reason or did you
> only forget to add the list? Imho this is interesting for others
> too.

well, it had an attachment that you can test which is not meant for 
context (to which i'll add a similar collapse feature, off by default of 
course as an escape) .. if that kind of stuff makes it into the latex 
font code is up to others

btw, i suppose most context enter composed glyphs anyway instead of 
separate thingies

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: decomposed and precomposde glyphs

[Ulrike Fischer]

Am Thu, 23 Feb 2017 14:08:54 +0100 schrieb Hans Hagen:

> btw, i suppose most context enter composed glyphs anyway instead of 
> separate thingies

But as my example (for the B with dot below) shows that this fails
if the font hasn't the precomposed glyph.

Also the problem is not so much to control the direct input but
copy&paste.  

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

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Re: decomposed and precomposde glyphs

[Hans Hagen]

On 2/23/2017 3:05 PM, Ulrike Fischer wrote:
> Am Thu, 23 Feb 2017 14:08:54 +0100 schrieb Hans Hagen:
>
>> btw, i suppose most context enter composed glyphs anyway instead of
>> separate thingies
>
> But as my example (for the B with dot below) shows that this fails
> if the font hasn't the precomposed glyph.
>
> Also the problem is not so much to control the direct input but
> copy&paste.

collapsing only can work for direct chars (so not \char for which we 
need that pseudo feature) ... when you put this on the first line it 
should do better

% directives="filters.utf.collapse=yes"

\starttext
     ạ ị Ạ g̣
\stoptext

should work (and it should be on by default which somehow it wasn't, 
probably disabled when i added some other input handling but no one 
noticed so far)

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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: decomposed and precomposde glyphs

[Ulrike Fischer]

Am Thu, 23 Feb 2017 14:08:54 +0100 schrieb Hans Hagen:

>> Did you sent the second mail only for me for a reason or did you
>> only forget to add the list? Imho this is interesting for others
>> too.
> 
> well, it had an attachment that you can test which is not meant for 
> context (to which i'll add a similar collapse feature, off by default of 
> course as an escape) .. if that kind of stuff makes it into the latex 
> font code is up to others

I looked at the code and it actually uses an idea that I had already
tried. The problem I couldn't solve was do decompose a glyph.
Looking at an context example it seems that context can do it. The B
with dot below (U+1E04) ends as BU+0323 in the pdf. But how does
context does it? It doesn't happen with a similar latex example.
There the U+1E04 is simply missing.

And why is the dot of the first B better placed than the second?
 

\starttext
\directlua
{
  fonts.handlers.otf.addfeature
  {
    name = "compose",
    type = "ligature",
    data =
        {
          ["Ạ"]={ "A", "̣" },
          ["Ḅ"]={ "B", "̣" },
        },
  }
}

\font\test={file:lmroman10-regular.otf:+compose;}

\test

Ḅ Ạ Ḅ %why are both B in the pdf???

\stoptext




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

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Re: decomposed and precomposde glyphs

[Hans Hagen]

On 2/23/2017 4:12 PM, Ulrike Fischer wrote:
> Am Thu, 23 Feb 2017 14:08:54 +0100 schrieb Hans Hagen:
>
>>> Did you sent the second mail only for me for a reason or did you
>>> only forget to add the list? Imho this is interesting for others
>>> too.
>>
>> well, it had an attachment that you can test which is not meant for
>> context (to which i'll add a similar collapse feature, off by default of
>> course as an escape) .. if that kind of stuff makes it into the latex
>> font code is up to others
>
> I looked at the code and it actually uses an idea that I had already
> tried. The problem I couldn't solve was do decompose a glyph.
> Looking at an context example it seems that context can do it. The B
> with dot below (U+1E04) ends as BU+0323 in the pdf. But how does
> context does it? It doesn't happen with a similar latex example.
> There the U+1E04 is simply missing.
>
> And why is the dot of the first B better placed than the second?
>
>
> \starttext
> \directlua
> {
>   fonts.handlers.otf.addfeature
>   {
>     name = "compose",
>     type = "ligature",
>     data =
>         {
>           ["Ạ"]={ "A", "̣" },
>           ["Ḅ"]={ "B", "̣" },
>         },
>   }
> }
>
> \font\test={file:lmroman10-regular.otf:+compose;}
>
> \test
>
> Ḅ Ạ Ḅ %why are both B in the pdf???
>
> \stoptext

it's not a ligature but a multiple

fonts.handlers.otf.addfeature
   {
     name    = "decompose",
     type    = "multiple",
     nocheck = true, -- new trick
     data    =
         {
           ["Ḅ"] = { "Q", "̣" },
           ["Ạ"] = { "X", "̣" },
         },
   }

as with all features we check against the font so of the font has no Ḅ
nothing happens and you won't see one either (as the font has no)

i'll add the nocheck option (but of course one can expect side effects 
when a font has nothing relevant)


-----------------------------------------------------------------
                                           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: decomposed and precomposde glyphs

[Arthur Reutenauer]

> I looked at the code and it actually uses an idea that I had already
> tried. The problem I couldn't solve was do decompose a glyph.
> Looking at an context example it seems that context can do it. The B
> with dot below (U+1E04) ends as BU+0323 in the pdf. But how does
> context does it?

  It uses the Unicode composition information (part of UnicodeData.txt),
they’re made into a Lua table in ConTeXt (named char-def.lua, if it
hasn’t changed).

	Best,

		Arthur
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Re: decomposed and precomposde glyphs

[Ulrike Fischer]

Am Thu, 23 Feb 2017 16:55:08 +0100 schrieb Hans Hagen:

> it's not a ligature but a multiple
> 
> fonts.handlers.otf.addfeature
>    {
>      name    = "decompose",
>      type    = "multiple",
>      nocheck = true, -- new trick


I updated my context version and changed my luaotfload.conf so that
it uses the context fontloader. Then the following plain tex
document (and a similar latex document) works and gives the wanted
output. 

BUT: If I uncomment the AU+0323 then I get a fatal error:

texmf-var/luatex-cache/generic/fonts/otl/lmroman10-regular.luc)table={
 [7684]={ 66, 803 },
}

! error:  (linebreak): invalid list tail, probably missing glue
!  ==> Fatal error occurred, no output PDF file produced!Drücken Sie
eine beliebige Taste . . .

(that's from the terminal output, the log doesn't show the
"table=..." part).


This "invalid list tail" is popping up now an then. Philip even
found a version were context crashed:
https://github.com/lualatex/luaotfload/issues/388


\input luaotfload.sty

\directlua
{
  fonts.handlers.otf.addfeature
  {
    name = "compose",
    type = "ligature",
    data =
        {
          ["Ạ"]={ "A", "̣" },
        },
  }
}
\directlua{
fonts.handlers.otf.addfeature
   {
     name    = "decompose",
     type    = "multiple",
     nocheck = true, 
     data    =
         {
           ["Ḅ"] = { "B", "̣" },
         },
   }
}
%\begin{document}
\font\test={file:lmroman10-regular.otf:mode=node;+decompose;+compose;}

\test

Ḅ Ạ % Ạ  %uncomment this to get a fatal error. 
Ḅ

\bye


With the standard fontloader of luaotfload there is no error but the
output is not correct. 

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

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Re: decomposed and precomposde glyphs

[Hans Hagen]

On 2/23/2017 6:26 PM, Ulrike Fischer wrote:
> Am Thu, 23 Feb 2017 16:55:08 +0100 schrieb Hans Hagen:
>
>> it's not a ligature but a multiple
>>
>> fonts.handlers.otf.addfeature
>>    {
>>      name    = "decompose",
>>      type    = "multiple",
>>      nocheck = true, -- new trick
>
>
> I updated my context version and changed my luaotfload.conf so that
> it uses the context fontloader. Then the following plain tex
> document (and a similar latex document) works and gives the wanted
> output.
>
> BUT: If I uncomment the AU+0323 then I get a fatal error:
>
> texmf-var/luatex-cache/generic/fonts/otl/lmroman10-regular.luc)table={
>  [7684]={ 66, 803 },
> }
>
> ! error:  (linebreak): invalid list tail, probably missing glue
> !  ==> Fatal error occurred, no output PDF file produced!Drücken Sie
> eine beliebige Taste . . .
>
> (that's from the terminal output, the log doesn't show the
> "table=..." part).
>
>
> This "invalid list tail" is popping up now an then. Philip even
> found a version were context crashed:
> https://github.com/lualatex/luaotfload/issues/388
>
>
> \input luaotfload.sty
>
> \directlua
> {
>   fonts.handlers.otf.addfeature
>   {
>     name = "compose",
>     type = "ligature",
>     data =
>         {
>           ["Ạ"]={ "A", "̣" },
>         },
>   }
> }
> \directlua{
> fonts.handlers.otf.addfeature
>    {
>      name    = "decompose",
>      type    = "multiple",
>      nocheck = true,
>      data    =
>          {
>            ["Ḅ"] = { "B", "̣" },
>          },
>    }
> }
> %\begin{document}
> \font\test={file:lmroman10-regular.otf:mode=node;+decompose;+compose;}
>
> \test
>
> Ḅ Ạ % Ạ  %uncomment this to get a fatal error.
> Ḅ
>
> \bye
>
>
> With the standard fontloader of luaotfload there is no error but the
> output is not correct.

I think that you cannot drop the new context code in an old otfload, 
because (1) afaik otfload patches code, and (2) because the context code 
assumes luatex 1.0.3 at least. Philip send me some test files a while 
ago so these bugs might have been fixed.

(There are no real fundamental changes, most is performance related and 
there have been improvements in discretionary handling. I have no clue 
if I added all relevant helpers to the generic code but normally  Philip 
checks that.)

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: decomposed and precomposde glyphs

[luigi scarso]

On Thu, Feb 23, 2017 at 6:26 PM, Ulrike Fischer <news3@nililand.de> wrote:
> Am Thu, 23 Feb 2017 16:55:08 +0100 schrieb Hans Hagen:
>
>> it's not a ligature but a multiple
>>
>> fonts.handlers.otf.addfeature
>>    {
>>      name    = "decompose",
>>      type    = "multiple",
>>      nocheck = true, -- new trick
>
>
> I updated my context version and changed my luaotfload.conf so that
> it uses the context fontloader. Then the following plain tex
> document (and a similar latex document) works and gives the wanted
> output.
>
> BUT: If I uncomment the AU+0323 then I get a fatal error:
>
> texmf-var/luatex-cache/generic/fonts/otl/lmroman10-regular.luc)table={
>  [7684]={ 66, 803 },
> }
>
> ! error:  (linebreak): invalid list tail, probably missing glue
> !  ==> Fatal error occurred, no output PDF file produced!Drücken Sie
> eine beliebige Taste . . .
>
> (that's from the terminal output, the log doesn't show the
> "table=..." part).
>
>
> This "invalid list tail" is popping up now an then. Philip even
> found a version were context crashed:
> https://github.com/lualatex/luaotfload/issues/388

https://bitbucket.org/phg/lua-la-tex-tests/src/tip/context/cnt-luatex-2-crash-kern-base.tex?fileviewer=file-view-default
\starttext
  \def \feats {+kern;mode=base} %% “node” works
  \definefontfeature [crash] [kern=yes,mode=base]
  \definedfont [file:Iwona-Regular.otf*crash]
  participated
\stoptext

no crash here with luatex 1.0.4 on my local box
(will commit soon to experimental)


-- 
luigi
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Re: decomposed and precomposde glyphs

[Ulrike Fischer]

Am Thu, 23 Feb 2017 18:41:28 +0100 schrieb Hans Hagen:


> I think that you cannot drop the new context code in an old otfload, 
> because (1) afaik otfload patches code,

Well not every fontloader version works, and it is always possible
that a too new (or too old) context fontloader breaks, but it
doesn't hurt to try

> and (2) because the context code  assumes luatex 1.0.3 at least.

Bingo. With luatex 1.0.4 it works and the fatal error is gone ;-)



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

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Re: decomposed and precomposde glyphs

[Hans Hagen]

On 2/23/2017 6:26 PM, Ulrike Fischer wrote:

> With the standard fontloader of luaotfload there is no error but the
> output is not correct.

btw, plain tests can be done with

mtxrun --script plain --make

mtxrun --script plain yourfile

(at least that is how Luigi and I test generic when plain crashes are 
reported)

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: decomposed and precomposde glyphs

[Ulrike Fischer]

Am Thu, 23 Feb 2017 18:45:04 +0100 schrieb luigi scarso:

> no crash here with luatex 1.0.4 on my local box

I just tried the lualatex examples with my luatex 1.0.4 too (I got
it from w32tex.org) and the error seems to be gone. 


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

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Re: decomposed and precomposde glyphs

[luigi scarso]

On Thu, Feb 23, 2017 at 6:50 PM, Ulrike Fischer <news3@nililand.de> wrote:
> Am Thu, 23 Feb 2017 18:45:04 +0100 schrieb luigi scarso:
>
>> no crash here with luatex 1.0.4 on my local box
>
> I just tried the lualatex examples with my luatex 1.0.4 too (I got
> it from w32tex.org) and the error seems to be gone.
ah w32tex.. right.
(offtopic)
So... can you check if the png/svg backed of mplib in luatex is still
available ?

-- 
luigi
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Re: decomposed and precomposde glyphs

[Ulrike Fischer]

Am Thu, 23 Feb 2017 17:20:05 +0100 schrieb Arthur Reutenauer:

>> I looked at the code and it actually uses an idea that I had already
>> tried. The problem I couldn't solve was do decompose a glyph.
>> Looking at an context example it seems that context can do it. The B
>> with dot below (U+1E04) ends as BU+0323 in the pdf. But how does
>> context does it?
> 
> It uses the Unicode composition information (part of UnicodeData.txt),
> they’re made into a Lua table in ConTeXt (named char-def.lua, if it
> hasn’t changed).

I know of char-def.lua but the question was more *how* the
information is used and *when*. In an input call back? Through a
font feature?

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

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Re: decomposed and precomposde glyphs

[Hans Hagen]

On 2/24/2017 10:35 AM, Ulrike Fischer wrote:
> Am Thu, 23 Feb 2017 17:20:05 +0100 schrieb Arthur Reutenauer:
>
>>> I looked at the code and it actually uses an idea that I had already
>>> tried. The problem I couldn't solve was do decompose a glyph.
>>> Looking at an context example it seems that context can do it. The B
>>> with dot below (U+1E04) ends as BU+0323 in the pdf. But how does
>>> context does it?
>>
>> It uses the Unicode composition information (part of UnicodeData.txt),
>> they’re made into a Lua table in ConTeXt (named char-def.lua, if it
>> hasn’t changed).
>
> I know of char-def.lua but the question was more *how* the
> information is used and *when*. In an input call back? Through a
> font feature?

in the case of the feature i sent you it's a font feature (so it 
operates on the stream of characters that the font machinery sees)

but in context we can also do it in the input (several ways)

Hans


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