Forum: Ruby-Gnome 2 Using Ruby/Poppler without an X display

Hello.

I'd like to use Ruby/Poppler in a server context (Rails application) to
render PDF documents.  However, it appears that the Poppler bindings
require the presence of an X display.  For example, the following code 
will
not run outside of an X session:

----
#!/usr/bin/ruby
require 'poppler'
require 'cairo'

filename = ARGV[0]

document = Poppler::Document.new(filename)
page = document.get_page(0)
(width, height) = page.size
surface = Cairo::ImageSurface.new(width_pt, height_pt)
context = Cairo::Context.new(surface)
page.render(context)
surface.write_to_png('test.png')
----

The code fails with:

/usr/lib/ruby/1.8/gtk2.rb:12:in `init': Cannot open display: 
(Gtk::InitError)
  from /usr/lib/ruby/1.8/gtk2.rb:12
  from /usr/lib/ruby/1.8/poppler.rb:6:in `require'
  from /usr/lib/ruby/1.8/poppler.rb:6
  from ./test_pdf.rb:2:in `require'
  from ./test_pdf.rb:2

(This is with ruby-gnome2 0.17, poppler 0.8.7 on Debian lenny)

AFAICT native Poppler itself can be used independently of an X session, 
so
it'd be nice to have a way to achieve this using the Ruby bindings.

What would need to be done to make this work?

Any suggestions on how to proceed would be much appreciated.

Regards,

-mato

Le mardi 31 mars 2009 à 00:25 +0200, Martin Lucina a écrit :
> What would need to be done to make this work?

Currently I think poppler will work fine without DISPLAY if you don't
have gtk2 binding installed but not if you have it :

begin
  require "gtk2"
rescue LoadError
end
begin
  require "cairo"
rescue LoadError
end

If you just remove LoadError to catch other exceptions while loading
gtk2 it may work

pterjan@linuxfr.org said:
> Currently I think poppler will work fine without DISPLAY if you don't
> have gtk2 binding installed but not if you have it :

I tried that, it didn't work:

/usr/lib/ruby/1.8/x86_64-linux/poppler.so: 
/usr/lib/ruby/1.8/x86_64-linux/poppler.so: undefined symbol: mGdk - 
/usr/lib/ruby/1.8/x86_64-linux/poppler.so (LoadError)
  from /usr/lib/ruby/1.8/poppler.rb:14
  from ./test_pdf.rb:2:in `require'
  from ./test_pdf.rb:2

There's some kind of dependency in there I don't understand...

-mato

Hi,

In <20090330232723.GG20372@nodbug.moloch.sk>
  "Re: [ruby-gnome2-devel-en] Using Ruby/Poppler without an X display" 
on Tue, 31 Mar 2009 01:27:24 +0200,
  Martin Lucina <mato@kotelna.sk> wrote:

> 
> There's some kind of dependency in there I don't understand...

Add the following code before "require 'poppler'":

  begin
    require 'gtk2'
  rescue Gtk::InitError
  end

Thanks,
--
kou

kou@cozmixng.org said:
> Add the following code before "require 'poppler'":
> 
>   begin
>     require 'gtk2'
>   rescue Gtk::InitError
>   end

Thanks Kou, that works.

Looks like I'll be using a different approach in any case, will write 
some
minimal Ruby bindings for MuPDF[1], since Poppler pulls in far too many
dependencies I don't really want installed on a server.

Thanks anyway!

-mato

[1] http://ccxvii.net/fitz/

A better approach might be to require 'gtk2/base' instead?  maybe 
poppler.rb should do that anyway...

Martin Lucina wrote:
> kou@cozmixng.org said:
>> Add the following code before "require 'poppler'":
>> 
>>   begin
>>     require 'gtk2'
>>   rescue Gtk::InitError
>>   end
> 
> Thanks Kou, that works.
> 
> Looks like I'll be using a different approach in any case, will write 
> some
> minimal Ruby bindings for MuPDF[1], since Poppler pulls in far too many
> dependencies I don't really want installed on a server.
> 
> Thanks anyway!
> 
> -mato
> 
> [1] http://ccxvii.net/fitz/