domingo, 11 de agosto de 2013

Qt in Debian: using Qt4 and/or Qt5 in your packages

Hi everyone! We now have both Qt4 and Qt5 in the archive. Those using Qt4 should not need to make any changes in their packages, although you can be extra-safe with a few steps. Don't rush, just read below.

Note 2014-12-12: the current official doc is available here.

Some background

Sune took the time some months ago to consult upstream for a sane way to allow both SDKs to coexist without us distros having to reinvent the wheel choosing which tools have to be in use in each case.

After a long discussion, upstream decided to write qtchooser (already in the archive) to be able to select between Qt4, Qt5 and even special user's cases like cross-platform builds.

So instead of going trough Debian's alternatives as we did with Qt3/Qt4, we will make use of this new tool.

My package uses Qt, how should I proceed?

There are many ways of choosing either of the versions of Qt:

- Using any qtchooser method (preferred):

  * Exporting QT_SELECT with 4, qt4, 5 or qt5 as a value in debian/rules.
  * Call the tool using the '-qtx' parameter, where x can be replaced with any of the options above.

- Build-depending on qt4-default or qt5-default. You can't B-D on both of them, as they can't coexist. Don't build depend nor depend on qt4-default and/or qt5-default.

It is good to notice that:

- any qtchooser method will take precedence over build depending on qtX-default.
- If you export XDG_CONFIG_DIRS it will ignore the default paths to qtchooser's configs we setted up in the packages.

We have also provided qt4-[arch-triplet] and qt5-[arch-triplet] options for special cases.

Once again, if you are already using Qt4, there is no need to rush. See below.

Can is use both Qt4 and Qt5 in my package?

You can't mix Qt4 and Qt5 in the same binary, but you may provide libraries compiled against one or the other. For example, your source package foo could provide both libqt4foo1 and libqt5foo1. You need to mangle your debian/rules and/or build system accordingly to achieve this. At the time of this writing I don't know of any examples yet.

So are you going to break the archive with a big transition?

No, we have done our best to avoid having to make any changes to existing Qt4 packages. Qt tools should default to Qt4 except if overriden by any method described above.

My package uses Qt4, can I leave it as it is?

While there is no need to apply the changes in this case, explicitly setting the Qt version will surely not hurt at all. But don't rush ;-) See note 2014-11-06

Note 2014-05-07: exporting XDG_CONFIG_DIRS is now safe.
Note 2014-07-26: We decided it's not good to build depend or even depend on qt4-default or qt5-default.
Note 2014-11-06: Qt4 will get removed in Jessie+1.
Note 2016-02-08: fixed doc URL.

domingo, 14 de julio de 2013

My experiences with KMail2 in Debian

Thanks to the Qt/KDE team, specially to Maxy who has done most of the packaging and uploading, sid users are now enjoying KDE 4.10.5, including the new KDE PIM stuff that we have held out for the Wheezy release.

I started using KMail2 (inside Kontact) a few days after Wheezy's release, getting it from experimental. And I have to admit that I really like it, just like with KMail1.

But my upgrade did have some bumps on the road, so I'm sharing them here so you can now how I solved them.

Mail import worked as we were waiting: it did work. So it was really useful to hold back Kmail1 until this really worked.

Now, I had a problem with my hard disk: whenever KMail started, it would start accessing it without pause. There where two reasons (for what I could test, I haven't looked at the source to really see if there was some other oddity) for this: I had a nepomuk/virtuoso DB created quite some time ago and initial mail indexing.

The initial mail indexing takes lots of time. For 1GB of DIMAP I had to wait like 5 hours (yes, 5 hours) on a 5600 rpm disk to let it fully finish. My desktop machine, with a faster hard drive, took a little less.

As far as people told me, that should have been enough, but my disk kept crawling. So I remembered someone from the team saying something about people with early-created nepomuk/virtuoso databases will have some speed issues. Mine where more than that, buy trying was worth the shot.

I had nepomuk disabled since I tried it the first version due to this exact problem. So I closed my KDE session and removed the nepomuk/virtuoso data:

rm -r ~/.kde/share/apps/nepomuk/

Then I logged back in KDE and waited (again) the 5 hours to let nepomuk re index my mail, this time totally finishing after 5 hours. Starting from that point, I get some one or two minutes of disk trashing some times I log in (not always), but it's actually not that bad. And I heard that in KDE 4.11 this has been improved a lot, so I should see a better behavior from that point on.

Please understand that this was my trial-and-error fix, it may be possible that someone comes with a better solution :-)

miércoles, 29 de mayo de 2013

Presenting qtchooser

A few days ago we the Qt/KDE team uploaded a new tool in the Qt ecosystem: qtchooser.

This tool is a wrapper tool used to select between different Qt versions. Of course, the first and easiest example is choosing between Qt4 and Qt5. But it doesn't end there: it can also be used to select a user's build of Qt.

To experienced Debian users, at first sight, it might resemble Debian's alternatives system. But it goes much further than that, allowing users (not sysadmins) to decide their defaults, and even adding new ones, user-wide. All this can be done using different methods like command line arguments, environment variables and configuration files.

Apart from all that, this is the recommended upstream way of managing Qt, being picked up by several (if not all) distributions, so it can easily be supported by upstream in their documentation.

My Qt4 package in Debian does not uses qtchooser, do I need to change anything?

No, we have tried to make things as smooth as possible. Your Qt4 packages should be safe. There will be more info on this later.

miércoles, 22 de mayo de 2013

Debian/Ubuntu packages caching and mobile workstations

Not so long ago I read Dmitrijs' blog post on how to configure apt-cacher-ng to advertise it's service using avahi. As I normally use my laptop in my home and at work, and both networks have apt-cacher-ng running, I decided to give it a try.

I have been administering apt-cacher-ng for three networks so far, and I really find it a useful tool. Then, thanks to the aforementioned blog post, I discovered squid-deb-proxy. I don't use squid, so it's not for my normal use case, but some people will surely find it interesting.

But I found it's client package to be really interesting. It will discover any service providing _apt_proxy._tcp through avahi and let apt use it. But then the package wasn't available in Debian. So, I contacted Michael Vogt to see if he was interested in putting at least the client in Debian's archive. He took the opportunity to upload the full squid-deb-proxy, so thanks a lot Michael :-)

I then filled a wishlist bug against apt-cacher-ng to provide the avahi configuration for publishing the service, which Eduard included in the last version of it. So thanks a lot Eduard too!


You know only need apt-cacher-ng >= 0.7.13-1 and avahi-daemon installed on your server and your mobile users just need squid-deb-proxy-client. Then the proxy autoconfiguration for apt will just work.

One again, thanks a lot to the respective maintainers for allowing this into Jessie :-)


Yes, there are still some rough edges. On one of the networks I'm behind a proxy. While configuring my machine to use apt-cacher-ng's service as a proxy trough apt.conf, apt-listbugs would just work. But now, using the service as discovered by squid-deb-proxy-client, apt-listbugs just times out. Maybe I need to fill some other bug yet...

miércoles, 15 de mayo de 2013

Qt 4.8.4 in experimental.

Since a few days we have Qt 4.8.4 (4:4.8.4+dfsg-3) in some archs of the experimental Debian archive. This release allows Qt4 to coexist with Qt5 while avoiding FTBFSs of current Qt4 packages in the archive.

So if you maintain a Qt4 app and want to check how it works with 4.8.4, you should be ready to go.

domingo, 21 de abril de 2013

On the road to Qt 5: Qt 5 base, tools, jsbackend and xmlpatterns in experimental

The first Qt 5 packages have been accepted in Debian experimental.

What's there

To start building Qt 5 apps you will need to export QT_SELECT=qt5, install the package qt5-defaults or read qtchooser's man page. Note that exporting QT_SELECT has precedence over installing qt5-defaults.

What's not there


AMD64 is already there because it's the arch used by maintainers to build the packages. i386 should be following as soon as buildds catch up. Most surely ARM-based archs will be there at some point too.

Other archs will need some love. Not strange, the Qt project supports amd64, i386 and ARM, but we Debian have normally prepared patches to make it build in other archs. And yes, we try to push them upstream for everyone's benefit. So, if you are missing it in your arch, take a look. You may be the one who enables Qt 5 in it :-)

GLES2 and Wayland

We don't have GLES2 or Wayland support yet. Building it will most probably break the desktop for people using proprietary video drivers (or at least I was told so). I'll surely provide non-official packages with GLES2/Wayland enabled to allow people testing it, but not soon.

This also means that we are not currently able to split X11 and framebuffer support. But we have time to work on it :-)

Non DFSGs compliant files

If you get the original source code tarball from Debian you will notice that it has dfsg in it's name. That means that we had to remove some non DFSG compliant stuff from the original tarball, namely:

  • Every RFC.
  • Three files used for testing the build, which are made of RFCs.
  • Some fonts.

What's following

Other parts of Qt 5 are on the way. And remember, this packages would not have been possible if it weren't for the great Debian's pkg-kde team. My kudos to them.

lunes, 1 de abril de 2013

On the road to Qt 5: Qt 4.8.4 and qtchooser uploaded to experimental

I have just uploaded Qt 4.8.4 to experimental. Apart from being the newest upstream release of the 4 series, it adds the basic support for coexisting with Qt 5. Because of this support it will need to go trough the NEW queue though, so we will need to be patient.

Developers will be interested in qtchooser, the tool that allows to switch between Qt 4 and 5 development apps. It has also been uploaded to experimental.

Of course, all this has been possible thanks to the efforts of the wonderful Qt/KDE team =)

Update: our efficacious FTP masters have already made Qt pass the NEW queue. Thanks a lot!

lunes, 25 de marzo de 2013

Entrevista en La Nueva Provincia

Hace unos dias Guillermo Burastero me llamó para comentarme que le habían pedido una nota en el diario local de Bahía Blanca, La Nueva Provincia, para que habláramos de software libre. La entrevista se concretó y he aquí el resultado (y acá en PDF).

Hice algunas menciones a Debian, pero bueno, no todo es posible a veces :-)

Tip: los nombres no coinciden con las fotografías. Les dejo adivinar el orden correcto ;-)

lunes, 18 de marzo de 2013

Día de la libertad del hardware

El sábado 20 de Abril se va a llevar a cabo el Hardware Freedom Day en todo el mundo, y Argentina no es excepción. Este año tenemos la suerte que se realice en dos lugares: La Plata (que cuenta con Alejo como uno de los coordinadores) y Buenos Aires.

A mi me van a quedar un poco lejos, pero invito al que pueda a acercarse al evento.

No se lo pierdan :-)

lunes, 4 de marzo de 2013

My Debian freeze experience (so far)

This is the first freeze in which I'm involved with upload rights. And it turned out to be a quite interesting ride so far, so I thought it would be nice to write about it.

As some of you may know, I'm a part of the Qt/KDE team. Before the freeze I was mostly involved in leaf packages, with some patch here or there, nothing fancy. And then the freeze came...

Bugs in Qt

...and bugs appeared in Qt. But they didn't get solved, even if the patches were there. Due to personal reasons, the manpower in Qt/KDE land decreased below normal levels (which were already low).

I took the time to review them, apply them in a local branch, build and test the fixes. I did a Qt upload before, but it was a team-consented one. This time there was not much reaction in our IRC channel as it used to be, so I was doubting if going ahead or not. I asked Ana, my great friend and former sponsor, for an opinion on the subject, and she gave me a really important advice: the patches were looking good and there is one really big true: if something get's broken, it can be fixed with a later upload.

You might be asking yourself why I was that afraid of doing the upload. Well, when one maintains such a medular package for many users one has to be careful  And I also got used that those "big ones" like Qt where normally handled by hand skilled people. Do not take me wrong here, it's not that those people where keeping them for themselves, it's knowing that one does not has the same skills nor experience as them.

But again, no one was able to upload and I had the chance and will to do another upload if needed, so off it went. That was Qt 4:4.8.2-2.

Then new experiences followed: asking a buildd maintainer for a giveback, asking the Release Team for an unblock (more on this later), etc. While sponsoring me, Ana gave me another excellent advice which I always keep in my mind:

You can't know **everything** about Debian.

And that also includes a not so technical skill: communicating with other teams. But finally we got this new version of Qt in testing. Cool :-)

Of course, new bugs appeared, and my lack of skills (and sometimes, time) where replaced by team work: Pino looking at patches and Sune contacting upstream. The eleven uploads that followed are a nice example of team work, even if I was the one who signed and did the uploads. Whoever uses Qt must know that these wonderful people (including those who are not so active nowadays like Modestas or Fathi) have done lots to bring the better to their users.Thank you guys!

Be careful, they might bite you back!

Coming back to the non-technical skills, sometimes you have to communicate with other teams in Debian. And each team is (naturally) a separate world: possibly different people, different goals, etc. Of course, we share the goal to make Debian the best experience we can, but we do not necessarily agree on the paths to achieve so.

During the freeze, there is a team that gets lots of pressure, and not by chance: the Release Team. They handle a very important task, which is to ride the freeze to get to a release. OK, that's what everyone knows. Now, one thing is knowing that and another is really understanding what does that means.

Of course I was in the first group. From the outside, communicating with the RT was a kind of "special art", and not an easy one. I have even been advised to not ask for more than one or two unblocks per weekend, as they might "bite me back". So I put on my flamesuit on and... launched reportbug

Now I'm really happy to say that my experience was far from what I described above. And yes, I had the chance to even disagree on some stuff. But remember: non-technical skills, a.k.a. social skills. Once I started to know what was going on inside the RT (joining #debian-release was a big help for that) I learnt some nice tips to approach them. Please allow me to list some of them:

  • Remember: you are the maintainer of the package, they are like gatekeepers that are there to help us coordinate to do a release. But they don't maintain the code, you do that. So try to be verbose when needed, explain the changes and don't forget a nice diff. They need to understand what is going on: they can't read your mind.
  • They are human beings too: not everyday might be their best day (the same goes for you too!). And they are under the pressure of a release. Be patient, that finally pays off.
  • Does your changes seem not so clear? try to improve them.
  • The package has a lot of changes but you really feel they are needed? Try to explain that as good as you can.
  • Try to put yourself in their position: do we really want this? If in doubt, there is a nice way to know what they think: a pre-approval bug.
I want to make a stop in this last point. A pre-approval bug it's an unblock bug in which you edit the subject to add "pre-approval" in it. Easy, isn't it? It gives you the opportunity to know what the RT thinks before doing the upload. In other words: it gives you the chance to communicate and do things in the best possible way for all the parts involved.

I've have also seen pre-approval bugs that were really not needed. But to learn where the threshold of what can be directly uploaded and what deserves a pre-approval bug is you need to know the guidelines the RT gives you. Do you still have doubts? fire a pre-approval bug and try to be clear.

Of course, this are all fruits of my experience with the RT during this time. If the RT thinks different from what I'm writing here, please stand up: we are hear to listen to you and learn :-)

As a side note, I think I should file a wishlist bug to include the pre-approval bug option in reportbug. Yes, I'm lazy :-)

Summing up

Overall this was a very nice and positive experience. We are not done yet. Are we really done at some point? Let's hope not, because this is where the fun comes from :-)