Re: [Tracker] fd.o compliant thumbnailing

[Erlend Davidson <E R M Davidson sms ed ac uk>]

Jamie McCracken wrote:
> Erlend Davidson wrote:
> > Jamie McCracken wrote:
> > > Erlend Davidson wrote:
> > >
> > > > That would require a whole standard for thumbnailers... the thunar 
> > > > ones take three or four command-line arguments (input file, size, 
> > > > output file and optionally the URI of the file), this should be 
> > > > sufficient, but someone might want more and then the standard would 
> > > > break.
> > > not really the same arguments are used by gnome in its gconf based 
> > > thumbnailers so its already a de facto standard. (A;though I dont 
> > > know what KDE uses?)
> > KDE is slightly different I think.  For example with kwebdesktop 
> > (which is used to thumbnail webpages),
> >
> > kwebdesktop 640 480 output_file input_file.
> >
> >
> > This is not an impossible problem to overcome however, as the thunar 
> > way of calling external thumbnailers involves the use of a .desktop 
> > file, like:
> >
> > ---< html-thumbnailer.desktop >---
> > [Desktop Entry]
> > Version=1.0
> > Encoding=UTF-8
> > Type=X-Thumbnailer
> > TryExec=kwebdesktop
> > MimeType=text/html;
> > Name=HTML Thumbnailer
> > X-Thumbnailer-Exec=kwebdesktop 640 480 %o %u
> >
> >
> > which can be used to change the order of arguments.
> > > > Incidently tracker uses the same command-line arguments as thunar 
> > > > for thumbnailers.  Coud you possibly change tracker to use the same 
> > > > directory as thunar?
> > > thats my point - the only thing not standardised is the location of 
> > > the scripts and thats why a freedesktop specified location would be 
> > > preferred by tracker.
> > I might e-mail the xdg list.
> > > In the short term, I can of course check for gnome thumbs using 
> > > GConfTool (which does not require linking in GConf) and as you say 
> > > the thunar directory if it exists so patches welcome for that.
> > >
> > > feel free to add a bugzilla enhancement request 
> > > (http://bugzilla.gnome.org) to tracker and I will get round to it 
> > > eventually if no patch is forthcoming
> > What area of the source should I look in to?
>
> src/trackerd/tracker-metadata.c
>
> function tracker_metadata_get_thumbnail
Actually it's src/tracker-thumbnailer/tracker-thumbnailer.c
just after the comment:
/* do we have a thumbnailer for this mime type? */

Is there an easy way to process .desktop files?  What needs to be done 
is all .desktop files in /usr/local/share/thumbnailers/ read and only 
those with "MimeType=argv[2]" selected.  Then read 
TryExec=DEPEND_ON_THIS_BINARY and check that DEPEND_ON_THIS_BINARY is 
executable and on the path, if so run the command specified by the key 
X-Thumbnailer-Exec.
e.g.  convert "ps:$ifile[0]" -scale "$sizex$size" "png:$ofile"