Re: PDF Viewer does not have continuous scrolling

[Riccardo Mottola]

Hi,



On 06/11/2016 10:46, Svetlana Tkachenko wrote:

ViewPDF 1:0.2dfsg1-5+b1 on Debian testing does not have continuous
scrolling. This inconveniences me as I read a line on page #N and I
can't view the next line on page #N+1 at the same time. I filed the bug
at the GAP bug tracker - please let me know if it is a wrong place. I
would appreciate it greatly if someone coded this feature or at least
added a comment with a bug fixing specification - which files to edit,
what to add.

https://savannah.nongnu.org/bugs/index.php?49544


GAP does not host ViewPDF.
GAP offers GSPdf which is essentially a GNUstep frontend to ghostscript 
(GS of gs :) )


I don't know where ViewPDF currently is hosted and if somebody maintains 
it at all - Is it another name for the old Vindaloo viewer?

I could trace that to:
http://gna.org/projects/gsimageapps 

Based on poppler.. it looks another piece of GS software that is 
bitrotting


I think that for  "continuous scrolling" you intend to see at the same 
time one page and the next page? GSPdf at least do not offer that and 
won't in any near future: it essentially render one page after the other 
via ghostscript.



Riccardo
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Re: PDF Viewer does not have continuous scrolling

[Svetlana Tkachenko]

Hi Riccardo,

Thanks for looking into this thoroughly - I am trying to grasp the
picture. Questions in-line below.

Riccardo Mottola wrote:
> Hi,
> 
> 
> 
> On 06/11/2016 10:46, Svetlana Tkachenko wrote:
> > ViewPDF 1:0.2dfsg1-5+b1 on Debian testing does not have continuous
> > scrolling. This inconveniences me as I read a line on page #N and I
> > can't view the next line on page #N+1 at the same time. I filed the bug
> > at the GAP bug tracker - please let me know if it is a wrong place. I
> > would appreciate it greatly if someone coded this feature or at least
> > added a comment with a bug fixing specification - which files to edit,
> > what to add.
> >
> > https://savannah.nongnu.org/bugs/index.php?49544
> 
> GAP does not host ViewPDF.
> GAP offers GSPdf which is essentially a GNUstep frontend to ghostscript 
> (GS of gs :) )

OK.

Riccardo Mottola wrote:
> I don't know where ViewPDF currently is hosted and if somebody maintains 
> it at all - Is it another name for the old Vindaloo viewer?
> I could trace that to:
> http://gna.org/projects/gsimageapps 
> 
> Based on poppler.. it looks another piece of GS software that is 
> bitrotting

Is being based on poppler bad? Is this software bad in its design?

I tried to compile PoppletKit for Vindaloo, and it gives me this error
even though I already installed libpoppler-dev and libpopplerkit0:

Making all for subproject bindings...
make[3]: *** No rule to make target 'obj/bindings.obj/poppler.c.o',
needed by 'obj/subproject.o'.  Stop.
/usr/share/GNUstep/Makefiles/Instance/subproject.make:45: recipe for
target 'internal-subproject-all_' failed
make[2]: *** [internal-subproject-all_] Error 2
/usr/share/GNUstep/Makefiles/Master/rules.make:311: recipe for target
'bindings.all.subproject.variables' failed
make[1]: *** [bindings.all.subproject.variables] Error 2
/usr/share/GNUstep/Makefiles/Master/rules.make:311: recipe for target
'PopplerKit.all.framework.variables' failed
make: *** [PopplerKit.all.framework.variables] Error 2

Riccardo Mottola wrote:
> I think that for  "continuous scrolling" you intend to see at the same 
> time one page and the next page? GSPdf at least do not offer that and 
> won't in any near future: it essentially render one page after the other 
> via ghostscript.

Is it useful for me to try GSPdf and edit it to add continuous scrolling
there?

What is a good starting point for getting continuous scrolling somehow
eventually?

Svetlana

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Re: PDF Viewer does not have continuous scrolling

[Riccardo Mottola]

Hi,


On 06/11/2016 21:22, Svetlana Tkachenko wrote:

I don't know where ViewPDF currently is hosted and if somebody maintains

it at all - Is it another name for the old Vindaloo viewer?
I could trace that to:
http://gna.org/projects/gsimageapps 

Based on poppler.. it looks another piece of GS software that is
bitrotting

Is being based on poppler bad? Is this software bad in its design?


Nothing bad being based on poppler.. I don't know the design of that 
program so I can't tell.
Poppler or xpdf can give at least some PDF functionality, while for 
ghostscript, like used in GSPdf, each page is just an image, there won't 
be stuff like search and I guess it will be always slower, but the 
rendering quality is quite high.

Different approaches.

The discussion of xpdf vs poppler then goes beyond this thread I guess.



I tried to compile PoppletKit for Vindaloo, and it gives me this error
even though I already installed libpoppler-dev and libpopplerkit0:

Making all for subproject bindings...
make[3]: *** No rule to make target 'obj/bindings.obj/poppler.c.o',
needed by 'obj/subproject.o'.  Stop.
/usr/share/GNUstep/Makefiles/Instance/subproject.make:45: recipe for
target 'internal-subproject-all_' failed
make[2]: *** [internal-subproject-all_] Error 2
/usr/share/GNUstep/Makefiles/Master/rules.make:311: recipe for target
'bindings.all.subproject.variables' failed
make[1]: *** [bindings.all.subproject.variables] Error 2
/usr/share/GNUstep/Makefiles/Master/rules.make:311: recipe for target
'PopplerKit.all.framework.variables' failed
make: *** [PopplerKit.all.framework.variables] Error 2


Sorry I don't know, never built that software myself.


Is it useful for me to try GSPdf and edit it to add continuous scrolling
there?

What is a good starting point for getting continuous scrolling somehow
eventually?


I can't think of an easy way of adding it in GSPdf. THink of GSPdf like 
an image viewer... one image after teh other, just that the images are 
your pages rendered to a /tmp


Riccardo

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Re: PDF Viewer does not have continuous scrolling

[Svetlana Tkachenko]

Dear Riccardo, 

Thanks a lot for your details about functional difference between
ghostscript and the xpdf/poppler PDF libraries. I appreciate it - I
probably wouldn't've figured it out if I didn't ask. I think text
selection is indeed useful for me to be able to take notes out of text
in the PDF documents so I will try to pursue the xpdf/poppler apps from
here.

Hopefully we figure out how to compile PopplerKit so that I can get
Vindaloo running. I will ask at the distribution channels and let you
know if I get enough help there.

Svetlana

Riccardo Mottola  wrote:
> Hi,
> 
> 
> On 06/11/2016 21:22, Svetlana Tkachenko wrote:
> > I don't know where ViewPDF currently is hosted and if somebody maintains
> >> it at all - Is it another name for the old Vindaloo viewer?
> >> I could trace that to:
> >> http://gna.org/projects/gsimageapps 
> >>
> >> Based on poppler.. it looks another piece of GS software that is
> >> bitrotting
> > Is being based on poppler bad? Is this software bad in its design?
> 
> Nothing bad being based on poppler.. I don't know the design of that 
> program so I can't tell.
> Poppler or xpdf can give at least some PDF functionality, while for 
> ghostscript, like used in GSPdf, each page is just an image, there won't 
> be stuff like search and I guess it will be always slower, but the 
> rendering quality is quite high.
> Different approaches.
> 
> The discussion of xpdf vs poppler then goes beyond this thread I guess.
> 
> >
> > I tried to compile PoppletKit for Vindaloo, and it gives me this error
> > even though I already installed libpoppler-dev and libpopplerkit0:
> >
> > Making all for subproject bindings...
> > make[3]: *** No rule to make target 'obj/bindings.obj/poppler.c.o',
> > needed by 'obj/subproject.o'.  Stop.
> > /usr/share/GNUstep/Makefiles/Instance/subproject.make:45: recipe for
> > target 'internal-subproject-all_' failed
> > make[2]: *** [internal-subproject-all_] Error 2
> > /usr/share/GNUstep/Makefiles/Master/rules.make:311: recipe for target
> > 'bindings.all.subproject.variables' failed
> > make[1]: *** [bindings.all.subproject.variables] Error 2
> > /usr/share/GNUstep/Makefiles/Master/rules.make:311: recipe for target
> > 'PopplerKit.all.framework.variables' failed
> > make: *** [PopplerKit.all.framework.variables] Error 2
> 
> Sorry I don't know, never built that software myself.
> 
> > Is it useful for me to try GSPdf and edit it to add continuous scrolling
> > there?
> >
> > What is a good starting point for getting continuous scrolling somehow
> > eventually?
> 
> I can't think of an easy way of adding it in GSPdf. THink of GSPdf like 
> an image viewer... one image after teh other, just that the images are 
> your pages rendered to a /tmp
> 
> Riccardo

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Re: PDF Viewer does not have continuous scrolling

[David Chisnall]

Poppler is based on xpdf (effectively the xpdf core refactored as a library).  
It isn’t a bad library, but due to its history it is GPLv2 (no ‘or later’ 
clause).  It was one of the main reasons that GNUstep remained LGPL2.1+ - 
moving to LGPLv3 would have made it incompatible with Poppler.  The GPL in 
Poppler also makes it difficult to put it in a library that can be used by 
other things (for example, if we want to do full-text searching in PDFs then we 
can’t use Apache Lucene, which is Apache licensed).

The FSF has a newer PDF library which is GPLv3+ (and was created largely 
because of Poppler’s license) and so addresses some of these issues (at least 
it’s Apache and LGPLv3 compatible).

Licensing aside, there’s no technical limitation why either approach couldn’t 
give you continuous scrolling, in the same way that TextEdit provides 
continuous scrolling of pages: you need to create a scroll view that includes 
multiple PDF views, one for each page.  A first cut at this should be under a 
hundred lines of code.  It’s a little bit more complicated to make efficient 
because each PDF page will be using a lot of memory and so you probably need 
work out which pages are visible in the scrollRangeToVisible: method and 
release ones that are more than a few pages away.

David

> On 6 Nov 2016, at 23:45, Svetlana Tkachenko  wrote:
> 
> Dear Riccardo, 
> 
> Thanks a lot for your details about functional difference between
> ghostscript and the xpdf/poppler PDF libraries. I appreciate it - I
> probably wouldn't've figured it out if I didn't ask. I think text
> selection is indeed useful for me to be able to take notes out of text
> in the PDF documents so I will try to pursue the xpdf/poppler apps from
> here.
> 
> Hopefully we figure out how to compile PopplerKit so that I can get
> Vindaloo running. I will ask at the distribution channels and let you
> know if I get enough help there.
> 
> Svetlana
> 
> Riccardo Mottola  wrote:
>> Hi,
>> 
>> 
>> On 06/11/2016 21:22, Svetlana Tkachenko wrote:
>>> I don't know where ViewPDF currently is hosted and if somebody maintains
 it at all - Is it another name for the old Vindaloo viewer?
 I could trace that to:
 http://gna.org/projects/gsimageapps 
 
 Based on poppler.. it looks another piece of GS software that is
 bitrotting
>>> Is being based on poppler bad? Is this software bad in its design?
>> 
>> Nothing bad being based on poppler.. I don't know the design of that 
>> program so I can't tell.
>> Poppler or xpdf can give at least some PDF functionality, while for 
>> ghostscript, like used in GSPdf, each page is just an image, there won't 
>> be stuff like search and I guess it will be always slower, but the 
>> rendering quality is quite high.
>> Different approaches.
>> 
>> The discussion of xpdf vs poppler then goes beyond this thread I guess.
>> 
>>> 
>>> I tried to compile PoppletKit for Vindaloo, and it gives me this error
>>> even though I already installed libpoppler-dev and libpopplerkit0:
>>> 
>>> Making all for subproject bindings...
>>> make[3]: *** No rule to make target 'obj/bindings.obj/poppler.c.o',
>>> needed by 'obj/subproject.o'.  Stop.
>>> /usr/share/GNUstep/Makefiles/Instance/subproject.make:45: recipe for
>>> target 'internal-subproject-all_' failed
>>> make[2]: *** [internal-subproject-all_] Error 2
>>> /usr/share/GNUstep/Makefiles/Master/rules.make:311: recipe for target
>>> 'bindings.all.subproject.variables' failed
>>> make[1]: *** [bindings.all.subproject.variables] Error 2
>>> /usr/share/GNUstep/Makefiles/Master/rules.make:311: recipe for target
>>> 'PopplerKit.all.framework.variables' failed
>>> make: *** [PopplerKit.all.framework.variables] Error 2
>> 
>> Sorry I don't know, never built that software myself.
>> 
>>> Is it useful for me to try GSPdf and edit it to add continuous scrolling
>>> there?
>>> 
>>> What is a good starting point for getting continuous scrolling somehow
>>> eventually?
>> 
>> I can't think of an easy way of adding it in GSPdf. THink of GSPdf like 
>> an image viewer... one image after teh other, just that the images are 
>> your pages rendered to a /tmp
>> 
>> Riccardo
> 
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Re: PDF Viewer does not have continuous scrolling

[Riccardo Mottola]

Hi,

David Chisnall wrote:

Poppler is based on xpdf (effectively the xpdf core refactored as a library).  
It isn’t a bad library, but due to its history it is GPLv2 (no ‘or later’ 
clause).  It was one of the main reasons that GNUstep remained LGPL2.1+ - 
moving to LGPLv3 would have made it incompatible with Poppler.  The GPL in 
Poppler also makes it difficult to put it in a library that can be used by 
other things (for example, if we want to do full-text searching in PDFs then we 
can’t use Apache Lucene, which is Apache licensed).


I do well know these licensing issues (the other being the Linux code in 
Terminal).
xpdf made a leap forward and was relicensed in its latest release and 
now contains the "or later clause". The stupid part is however that I 
can't get PDFKit to work with the newer version, they removed one of the 
options needed to work as a library.
I made several attempts but failed failed and lost time. It would be 
nice to collaborate with the guy.


Riccardo

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Re: PDF Viewer does not have continuous scrolling

[Svetlana Tkachenko]

Dear Riccardo,

> they removed one of the 
> options needed to work as a library.

Which option? Here is the xpdf upside-down (!) change-log:
http://www.foolabs.com/xpdf/CHANGES

Would you like me to forward your email to derekn 
and ask them to bring the option back? As mentioned at
http://www.foolabs.com/xpdf/home.html, http://freecode.com/projects/xpdf
? It is the right version, yes?

Svetlana

Riccardo Mottola  wrote:
> Hi,
> 
> David Chisnall wrote:
> > Poppler is based on xpdf (effectively the xpdf core refactored as a 
> > library).  It isn’t a bad library, but due to its history it is GPLv2 (no 
> > ‘or later’ clause).  It was one of the main reasons that GNUstep remained 
> > LGPL2.1+ - moving to LGPLv3 would have made it incompatible with Poppler.  
> > The GPL in Poppler also makes it difficult to put it in a library that can 
> > be used by other things (for example, if we want to do full-text searching 
> > in PDFs then we can’t use Apache Lucene, which is Apache licensed).
> 
> I do well know these licensing issues (the other being the Linux code in 
> Terminal).
> xpdf made a leap forward and was relicensed in its latest release and 
> now contains the "or later clause". The stupid part is however that I 
> can't get PDFKit to work with the newer version, they removed one of the 
> options needed to work as a library.
> I made several attempts but failed failed and lost time. It would be 
> nice to collaborate with the guy.
> 
> Riccardo
> 
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Re: PDF Viewer does not have continuous scrolling

[Riccardo Mottola]

Hi,

Svetlana Tkachenko wrote:

Which option? Here is the xpdf upside-down (!) change-log:
http://www.foolabs.com/xpdf/CHANGES

Would you like me to forward your email to derekn
and ask them to bring the option back? As mentioned at
http://www.foolabs.com/xpdf/home.html,http://freecode.com/projects/xpdf
? It is the right version, yes?


the xpdf bridge uses a special "pdfkit" target in the xpdf makefile. I 
don't remeber now how this interacted with xpdf. I essentially need to 
compile xpdf as a library and without X. this special target needed to 
compile certain things "only" in xpdf...


I attempted that over a year ago without success. I can try again, but 
only if I can get some help. It would be really excellent to get all 
those fixes and especially the license change! I will try to reconstruct 
what the special pdfkit target needed.


Riccardo

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Re: PDF Viewer does not have continuous scrolling

[Riccardo Mottola]

Hi,

Riccardo Mottola wrote:
the xpdf bridge uses a special "pdfkit" target in the xpdf makefile. I 
don't remeber now how this interacted with xpdf. I essentially need to 
compile xpdf as a library and without X. this special target needed to 
compile certain things "only" in xpdf...


I attempted that over a year ago without success. I can try again, but 
only if I can get some help. It would be really excellent to get all 
those fixes and especially the license change! I will try to 
reconstruct what the special pdfkit target needed. 


I started working on this again - I was able to reinstantiate the old 
target for now and the main issues I have is that the bridge needs to be 
updated: several methods changed and need to be updated and not 
everything appears super-trivial at a first glance.
I commited the sources of 3.04 in the SVN repository, they contain 
already the changes in the makefiles, however everything is set-up 
against 3.02 so no harm yet.


Someone wants to share the pain? I can share the current patch I have, 
build still fails though.


Stefan, are you still with us? would be nice, after soo many years! :)

Riccardo

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