[erlang-questions] ErlGuten + a short survey

Wed Sep 26 09:04:21 CEST 2018

As you know I will at some point[0] want to make Asciidoc produce PDF 
files so I may end up wanting to use it. However from what I've seen so 
far I'm not sure it would be very helpful.

My main concern is that from the Asciidoc I get an AST that has little 
pagination information attached. I would therefore need to go from that 
Asciidoc-AST to a sort of PDF-AST which comes with pagination 
information and can then be used to generate the PDF using the PDF 
drawing primitives. I have not seen code to automatically paginate in 
erlguten/erlpress_core but maybe I missed it. Then there's all the 
concerns about table of contents, figure listings and whatnot.

Writing the PDF itself could be done by erlguten/erlpress_core, but it 
could also just be building an iolist on the fly like I do for man 
pages[1]. This would be similar to what projects like PHP's fpdf library 
are doing. Writing the PDF is not a big concern either way since 
Asciidoc has limited capabilities compared to PDF.

In other words, as far as I can tell so far, erlguten seems to solve a 
different problem than the one I am mainly concerned with. But I've only 
done a cursory examination of erlguten/erlpress_core so it's possible 
that I missed something.

[0] This or next Christmas. Probably.
[1] https://git.ninenines.eu/asciideck.git/tree/src/asciideck_to_manpage.erl

On 09/25/2018 09:42 PM, lloyd@REDACTED wrote:
> Hi folks,
> 
> As Theepan says,  "PDF generation library is crucial to most of the commercial
> applications."
> 
> If you are using ErlGuten, please help inform my work on erlpress_core:
> 
> 1. What are you using it for?
> 2. What features do you wish it has but doesn't?
> 
> Many thanks,
> 
> Lloyd
> 
> -----Original Message-----
> From: "Theepan" <vasdeveloper@REDACTED>
> Sent: Tuesday, September 25, 2018 2:55pm
> To: "Lloyd Prentice" <lloyd@REDACTED>
> Cc: "Erlang Questions Mailing List" <erlang-questions@REDACTED>, "Joe Armstrong" <erlang@REDACTED>
> Subject: Re: [erlang-questions] ErlGuten
> 
> Hi Lloyd,
> 
> You are right. PDF generation library is crucial to most of the commercial
> applications. The code base is not very complicated, but then again we need
> somebody who has time and willingness to take on the work. Please find what
> have written to Sean on what improvements can be crucial short term.
> 
> Wish work arounds and short fixes we could achieve the required scemantics,
> performance and throughput out of ErlGuten.
> 
> Best,
> Theepan
> 
> 
> 
> On Tue, Sep 25, 2018 at 10:21 PM <lloyd@REDACTED> wrote:
> 
>> Hi Theepan,
>>
>> Other than display in my demo PDF, I haven't worked much with images.
>>
>> The issues you've run across seem serious. Getting at the root of the
>> problems will likely involve a deep dive into both the PDF reference
>> manuals and core ErlGuten source code.
>>
>> As I noted in my earlier email, ErlGuten source code is very challenging.
>> It would benefit significantly from re-write, possibly refactoring in some
>> cases and definitely systematic documentation of functions and parameters.
>>
>> I'm not confident that my skills are up to this. My take is that it would
>> require some amount of community effort to put ErlGuten/erlpress_core on a
>> solid, maintainable base. I would dearly love to see this happen.
>>
>> Is there a CS major or intern out there with time to take on the
>> challenges?
>>
>> Joe showed us the way and I, for one, am deeply grateful. Given that PDF
>> is a significant standard in the print media world, Erlang deserves to have
>> a world-class library and suite of tools to generate PDF documents and
>> decode them back into Erlang structures.
>>
>> This will take community effort.
>>
>> All the best,
>>
>> Lloyd
>>
>>
>>
>>
>>
>> -----Original Message-----
>> From: "Theepan" <vasdeveloper@REDACTED>
>> Sent: Monday, September 24, 2018 7:27pm
>> To: "Lloyd Prentice" <lloyd@REDACTED>
>> Cc: "Erlang Questions Mailing List" <erlang-questions@REDACTED>, "Joe
>> Armstrong" <erlang@REDACTED>
>> Subject: Re: [erlang-questions] ErlGuten
>>
>> Wanted to add to the issues the reasons --
>>
>> ** When some JPEG image is embedded into the PDF, it turns out dark in the
>> generated PDF file [Happens due to CYMK color profile.]
>> ** When some PNG file is embedded, it takes too long (unto 5 minutes) to
>> generate the PDF file. Debugging shows that the delay is on defilter(Method
>> , Line1, Line2, Offset, Width, Iter) of eg_pdf_image module.[Happens due to
>> Alpha channel presence]
>>
>>
>>
>> On Tue, Sep 25, 2018 at 4:45 AM Theepan <vasdeveloper@REDACTED> wrote:
>>
>>> Thanks Lloyd for your detailed explanation on what has been done, and
>> your
>>> vision for the library. However we are already using ErlGuten in one of
>> our
>>> production systems, and the issues is mainly with the images.
>>>
>>> I will definitely keep an eye on the development of erlpress_core in the
>>> future, as you seem enthusiastic about making it a lively library.
>>>
>>> The issues we have are:
>>>
>>> ** When some JPEG image is embedded into the PDF, it turns out dark in
>> the
>>> generated PDF file
>>> ** When some PNG file is embedded, it takes too long (unto 5 minutes) to
>>> generate the PDF file. Debugging shows that the delay is on defilter(
>>> Method, Line1, Line2, Offset, Width, Iter) of eg_pdf_image module.
>>>
>>> Did you come acrsoss this?
>>>
>>> Best,
>>> Theepan
>>>
>>>
>>>
>>>
>>>
>>> On Tue, Sep 25, 2018 at 2:56 AM <lloyd@REDACTED> wrote:
>>>
>>>> Hi Theepan,
>>>>
>>>> 1. If you look at ErlGuten source, you'll see that function
>> documentation
>>>> is fairly minimal and many parameters have single character names with
>>>> little to no documentation. This makes maintenance and revision very
>>>> difficult. I consider the core ErlGuten modules diamonds-in-the-rough.
>>>>
>>>> I also found the high-level page make-up functions provided by Hugh and
>>>> Carl limited with respect to professional page make-up and, to me at
>> least,
>>>> a bit confusing.
>>>>
>>>> But erlpress_core owes a deep debt and much gratitude to the ErlGuten
>>>> lineage.
>>>>
>>>> erlpress_core is based on Joe's font-handling, justification, and XML
>>>> parsing code with few if any changes. But it provides map structures to
>>>> represent nearly all of the PDF objects represented in eg_pdf_op.erl.
>> These
>>>> map structures incorporate many default parameters so generating PDF
>>>> documents is syntactically simple and consistent without sacrificing
>>>> expressive flexibility. You can easily customize display by
>> instantiating
>>>> map parameters with your own values.
>>>>
>>>> You can see most of the PDF objects currently supported by
>> erlpress_core,
>>>> including boxed text, justification options, and various line and text
>>>> objects, demonstrated in ep_show_n_tell.pdf and the source in
>>>> ep_show_n_tell.erl.
>>>>
>>>> If you look at the map definitions of the various PDF objects, you'll
>> see
>>>> how to customize display.
>>>>
>>>> At some point if would be good to re-write the base Erlguten modules
>> with
>>>> more explicit function and parameter documentation, but I'm not up to
>> that
>>>> at this point. But, anyone looking for a challenge is free to jump in.
>>>>
>>>> I'm currently working on tables and text flow across pages (think
>> reports
>>>> and book chapters). Hope to deliver these features plus much code
>> polishing
>>>> in the next release coming "real soon now."
>>>>
>>>> High on my wish/to-do list are:
>>>>
>>>> -- Easy-to_use page-grid design functions
>>>> -- Imposition (printing multiple page impressions on a single sheet of
>>>> paper stock)
>>>> -- Articles and beads (think text jumping across  columns and pages)
>>>> -- Easy-to-use and expressive page make-up functions
>>>> -- Example templates for various print formats
>>>> -- Markdown input
>>>> -- Support of TTF and OTF fonts
>>>>
>>>> Joe Armstrong expressed the following goal when he first announced
>>>> ErlGuten:
>>>>
>>>> "Better than TeX."
>>>>
>>>> That's a tall order, yet to be realized. My hope is that erlpress will
>>>> move the ball further down the field.
>>>>
>>>> 2. I haven't done anything with image formats beyond what you'll find in
>>>> eg_pdf_image.erl. I'd welcome work in that direction.
>>>>
>>>> 3. erlpress_core is still at Version 0.01. It's just out. I'm working
>>>> toward sufficient functionality and stability to support a web
>> application
>>>> that we have currently under development.
>>>>
>>>> 4. I developed erlpress_core on Erlang/OTP 19. It does require support
>>>> for maps.
>>>>
>>>> I see the erlpress_core library as a valuable library for embedding PDF
>>>> generation into Erlang applications and as the basis for many exciting
>>>> Erlang-based print production tools.
>>>>
>>>> So, Treepan, I appreciate your interest and would welcome your
>>>> involvement in testing and feature development.
>>>>
>>>> I would jump for joy if some Erlang guru were to step forward take on
>> the
>>>> TTF/OTF support issue. I've done some research and have a few ideas on
>> how
>>>> expanded font support might be accomplished, but have too little time
>> over
>>>> the next several months to dig into it.
>>>>
>>>> Incidentally, in my previous post my iPad decided it was smarter than me
>>>> and erroneously corrected my GitHUb address.it should be
>>>> writersglen/erlPress_core.
>>>>
>>>> My intention is to bag the camel case in my next release with luck in a
>>>> week or two so it should look like writersglen/erlpress_core.
>>>>
>>>> All the best,
>>>>
>>>> Lloyd
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: "Theepan" <vasdeveloper@REDACTED>
>>>> Sent: Monday, September 24, 2018 3:59pm
>>>> To: lloyd@REDACTED
>>>> Cc: "Erlang Questions Mailing List" <erlang-questions@REDACTED>, "Joe
>>>> Armstrong" <erlang@REDACTED>
>>>> Subject: Re: [erlang-questions] ErlGuten
>>>>
>>>> Hi Lloyd,
>>>>
>>>> Thank you for your response. I have some quick clarifications --
>>>>
>>>> * What are the major improvements made on the source ErlGuten? Did you
>>>> improve support to different image formats? Any critical bugs fixed?
>>>> * Is erlPress_core used in commercial applications, specifically of high
>>>> throughput types?
>>>> * What is the minimum erlang/OTP version required?
>>>>
>>>> Best,
>>>> Theepan
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> On Mon, Sep 24, 2018 at 6:36 AM Lloyd R. Prentice <
>> lloyd@REDACTED>
>>>> wrote:
>>>>
>>>>> Hi Thepan,
>>>>>
>>>>> I’ve undertaken a major revision of ErlGuten called erlPress_core—
>>>>> announced it on Erlang questions several weeks ago.  It’s available
>> from
>>>>> GitHub as Writersglen/erlPress_core. I think you’ll find it much more
>>>>> accessible than the ErlGutens.
>>>>>
>>>>> I’ve since been polishing up the code and adding a few new features.
>>>> After
>>>>> the launch I learned that camel case is not conventional usage when it
>>>>> comes to the names of Erlang applications and libraries. So I plan to
>>>>> release the updated version as erlpress_core. With smooth sailing I
>>>> hope to
>>>>> release sometime this week or next.
>>>>>
>>>>> All the best,
>>>>>
>>>>> Lloyd
>>>>>
>>>>> Sent from my iPad
>>>>>
>>>>> On Sep 23, 2018, at 8:30 PM, Theepan <vasdeveloper@REDACTED> wrote:
>>>>>
>>>>>
>>>>> Hi Team,
>>>>>
>>>>> I see many forks of ErlGuten. Which one is the latest, most stable and
>>>>> widely used?
>>>>>
>>>>> https://github.com/richcarl/erlguten
>>>>> https://github.com/CarlWright/NGerlguten
>>>>> https://github.com/hwatkins/erlguten/commits/master
>>>>>
>>>>> Best,
>>>>> Theepan
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> erlang-questions mailing list
>>>>> erlang-questions@REDACTED
>>>>> http://erlang.org/mailman/listinfo/erlang-questions
>>>>>
>>>>>
>>>>
>>>>
>>>>
>>
>>
>>
> 
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-- 
Loïc Hoguin
https://ninenines.eu