Re: [Tracker] Are thumbnails from trackerd really useful?

[Jamie McCracken <jamiemcc blueyonder co uk>]

Laurent Aguerreche wrote:
> Le dimanche 10 septembre 2006 Ã 17:16 +0100, Jamie McCracken a Ãcrit :
> > Laurent Aguerreche wrote:
> > > Hello,
> > >
> > > currently trackerd generates thumbnails for PDF files. I just wonder
> > > whether it is useful!
> > >
> > > To have this feature, trackerd calls evince (which depends on many
> > > components of X and GNOME...) and those calls slowdown a little bit
> > > trackerd.
> > >
> > > Graphical shells, like Nautilus, Konqueror or Thunar, are supposed to
> > > know how to make thumbnails from files, and I have already many
> > > generated thumbnails in ~/.thumbnails. So I think that trackerd should
> > > not do thumbnails and let other programs do it by themselves.
> > >
> > > Am I missing something?
> > Yes.
> >
> > Doing it in tracker means you wont have to wait for file managers to 
> > thumbnail.
>
> Yes but I don't care about that! IMHO trackerd should be dedicated to
> extract datas from documents for research, and only for research.
>
> In future if trackerd does a thumbnail for each indexed file it will
> spend something like an equal, or greater, time for this task than for
> extracting datas.
> Furthermore I know that I have some documents that I won't never open
> because they are in archives, in big projects, etc. So while trackerd is
> losing its time with thumbnailing for documents that I won't never open,
> live queries aren't as responsives as they could be for instance.
>
> > However:
> >
> > 1) thumbnails should be optional so feel free to add an option to 
> > disable them.
>
> Ok. So I propose a patch.

thanks patch is good and now committed.
> (default is DoThumbnails=true...)
>
> > 2) They dont use the freedesktop spec for thumbnails yet. This is a bug 
> > and a fix would be nice
> > http://lists.freedesktop.org/archives/xdg/2004-October/005067.html
>
> But a fix doesn't seem to be so easy!
> Names in ~/.thumbnails/{normal,large,fail} are md5 hashes. I think it
> isn't a problem since there is a free (in public domain) implementation
> available in libgnomeui (it just takes time to compute uri). But
> problems come right after: thumbnails need to be resized and tagged. In
> libgnomeui, GDK is used. Since GDK is dependent to X, a replacement
> should be found...

MD5 hash does not require gnome. (mysql has a function for it built in 
but as md5's code is so small you could inline the source for it in 
tracker-utils.c)

Its easy to fix and efficient too. Tracker would simply check the mtime 
of the existing thumbnail in ~./tumbnails before deciding whether to 
call a thumbnailer.

Thumbnails are important for a tracker search gui and a possible tracker 
backed file manager which I plan to write some day!

> > 3) long term plan is to add *optional* gconf facility for replacing the 
> > config file and getting access to all the the thumbnailers defined in 
> > gconf (see keys /desktop/gnome/thumbnailers in gconf-editor)
>
> Hum... and a corresponding thing for KDE's users?   ;-)

Im not a c++ programmer and there are no C bindings to KConfig so would 
need a volunteer to do this.

> It could be interesting to have a way to change options dynamically.
> With DBus?

maybe but that would mean updating the backing store too (gconf, ini 
file, kconfig etc) so might be tricky.



--
Mr Jamie McCracken
http://jamiemcc.livejournal.com/