Specifying thumbnailers as a service

Lubos Lunak l.lunak at suse.cz
Mon Sep 1 04:59:43 PDT 2008

On Monday 01 of September 2008, Philip Van Hoof wrote:
> On Mon, 2008-09-01 at 10:25 +0200, Lubos Lunak wrote:
> > On Friday 29 of August 2008, Philip Van Hoof wrote:
> >
> >  Is this API also intended to be used by filemanagers? It appears to have
> > several performance problems for use in those:
> >
> > - there is no notification about progress (i.e. when a thumbnail is
> > done), so a filemanager showing a directory would have to wait for all
> > thumbnails created there (unless it wants to watch the thumbnail
> > directories for a change). Also, even if there was such a signal, it
> > would probably be nice to also have a request for cancelling the create
> > request, in order to change what should be generated when the user
> > scrolls around in a view with many files
> I have not seen many other thumbnailers have progress or status
> information.

 You mean, besides those built-in in image viewers or file browsers.

> I think canceling is overkill. Making a thumbnail doesn't take longer
> than a minute (and a minute is an extreme case). Users don't cancel
> that.

 It wasn't meant for a user. If the user scrolls the view, then the visible 
files should get thumbnails first. The simplest idea seemed to be cancelling 
and starting anew. (This was meant under the assumption that it would be for 
real-time generation of thumbnails, which appears to be false.)

> > - thumbnail generators usually don't go via saving to disk but use some
> > more efficient way (e.g. pass data in-process)
> Passing pixbuf data over IPC doesn't sound very efficient to me. I also
> wonder why you would do that over IPC?!
> Just make a library that does it for your application (like your
> `create_image` below).

 I'll take this as "no" to my original question about whether your proposal is 
also meant for apps like file managers (i.e. real-time generation). In that 
case, however, I suggest you use a better fitting name. A thumbnailer I would 
say is something that creates a thumbnail (that is, a picture) out of a file. 
What you are suggesting is thumbnail management.

> For some files (and file-types) will the generation of a thumbnail take
> a lot of time, so when most applications request a thumbnail, they mean:
> 	"create me the thumbnailcache for this file and callback"
> when they request the creation of the thumbnail.

 The problem already exists even now, doesn't it? And presumably has been 
already solved somehow.

> For the purpose of specifying the storage of that cache, we already have
> 	http://jens.triq.net/thumbnail-spec/index.html
> This proposal is about specifying requesting the creation of a thumbnail
> in that cache.
>    ^^^^
> You can of course still make a library that just creates the thumbnail.

 So, again, this is not about thumbnailers, this is about thumbnail management 
then. It was not clear to me from your original mail.

Lubos Lunak
KDE developer
SUSE LINUX, s.r.o.   e-mail: l.lunak at suse.cz , l.lunak at kde.org
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190 00 Prague 9      fax: +420 284 028 951
Czech Republic       http://www.suse.cz

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