Sunday, November 25, 2012

KDE, Qt, and the segv

Short story: qt-4.8.4 on Fedora 16 might offer you crashes when clicking the menu in the panel. I had this on my main user account, but not another account. Downgrading to 4.8.3 solved this with the exact same .kde, .local et al in place.

The crashes offered my g_iterator type things in the backtrace. Nothing juicy that I could try to work backward from. Digging around seemed to show theme stuff, pointing at the nvidia drivers (which always comes up in searches), and there was a bug I found along the way mentioning qt 4.8.4, so I reverted to 4.8.3 from a mirror that had the old packages still around.

I decided to update the laptop before a trip on thursday, and this was of course when I discovered this little bundle of joy. I'm not sure which part of my config was causing this, but at least I can now use the laptop with my desktop of choice while away!

Wednesday, November 21, 2012

Libferris as a KIO Slave

The libferris virtual filesystem can now be exposed as a KIO Slove too. This allows you to use KDE applications to list, read and write the vast number of virtual filesystems that libferris makes available. For those who don't know, ferris is a little project I've been working on over the last decade to make everything a file: XML, db, relational data, web services, and even applications like XWindow, Amarok, pulseaudio, and gstreamer.

The following will create a Berkeley db4 file from the command line and show it to you. To dig into such files with libferris you can just read the file directly. So in this case I just grab the "base" directory in this db4 file with konq. You should see the sample and file2 files in that directory view and be able to load and save those "files" into kwrite. Sorry about the video being a tad jumpy, I have to work out what part of my desktop is causing that :/

Using libferris through the KIO interface from Ben Martin on Vimeo.

The commands as plain text:

$ cd /tmp
$ db45_load -T -t btree foo.db
value here

$ db_dump -p foo.db
$ konqueror ferris:/tmp/foo.db/base

little tricks I found during the hacking, your listDir() method might call listEntry( e, false ) with a final call using ( e, true ). The last call is impotent with regard to "e" and just a finalizer call. The get() method uses data() to deliver bytes to the KIO user (application). The put() method uses dataReq() in a loop to grab chunks frrom the KIO user. Currently I have lazy methods, for example the put() just grabs everything from the KIO user and then operates on the data once it has everything. Really bad for 4gb files, but for smallish files to get a feel for things it works quite well.

Also, if you are using library init, in my case using gmodule to dynamically load some plugins from libferris itself, you might be in for a world of fun and games. Currently I spawn processes and interact with them from the KIO slave to get around this issue. I imagine for a more efficient implementation being able to tell KDE to load my KIO Slave as an application with a normal full init leading to a main() but haven't looked at that little technicality yet.

I've mostly been tinkering with kioclient, konq, and kwrite on libferris files at the moment. Things are turning out well, though there are still many glitches to this early days integration. This will be released in the next libferris version once I clean it up a bit more.

Monday, November 19, 2012

Mounting KIO with libferris

I know there are more folks interested in going the other way -- seeing libferris through kio glasses. Not that there are hoards of folks in either camp of course. Nonetheless the first move has been to allow libferris to mount kio.

The groundwork is very similar to what I'm thinking of using to allow kio to mount libferris. Top level URL schemes will appear first, allowing you to dig into each URL scheme. For example, in libferris kio appears under the kio: filesystem. The first directory in that filesystem is the KIO URL scheme to use. So something like the following will work:

$ date >| /tmp/df.txt
$ fcat kio:file:/tmp/df.txt

Some of the more fun KIO slaves to access through this are the man and fonts URLs. The following two commands produce the same man page:

$ fcat kio:man:/man
$ kioclient cat man:/man

Support is preliminary and only allows reading the files but not writing to them through the kio: filesystem as yet. Already though the kio: can be exposed to XQuery, SQLite, and through the libferris REST interface. Yay for cooperating!

I notice some really juicy digikam kio slaves but haven't dug into them enough to use them as yet. Although you can already upload to various web services from digikam, once I get access to digikamalbums through ferris kio mounting I can then 'cp' the images directly from the command line to other things that libferris can already mount such as flickr API sites, printers etc.