A picture is worth a thousand words:

A slightly longer story follows, resuming from the previous episode, where Gtk seemed to be working.

Making sure Gtk actually works

Since the udebs are quite fat already, I decided to put the contents of the gtk2.0-examples package into a new revision of the new libgtk-x11-udeb package. gtk-demo was running fine (if one forgets that this demo application is really easier to deal with if one uses a window manager), although image handling was broken. Julien and I spent quite some time double-checking that the libpixbufloader-png.so plugin was present; that both previous DirectFB-based udeb and new x11-based udeb were very similar; that configuration was generated properly; we went so far as to include strace in the netboot image, and to check the configuration file was open()’d, but the plugin was never to be even looked for. All this resulting in a Unrecognized file format message every time.

Josselin, our Messiah, enlightened us: although Gtk was previously using some configuration files to determine which pixbufloader plugin to use, it still continues to access those files… but relies on a MIME database in the end. Installing the host’s /usr/share/mime/mime.cache database did the trick (we have a proper fix pending), and all of a sudden, we got image support (which is needed for the logo_installer.png displayed on top of every screen, as well as for some icons during the installation, like the final one).

Tweaking d-i itself

Julien took care of rootskel-gtk. It was mostly about:

• Dropping some DirectFB start-up scripts.
• Dropping a related configuration file.

• Adding a start-up script doing trivial things:

   Xorg -retro -noreset &
   export DISPLAY=:0
  

Another easy step was cdebconf. Mostly: search and destroy on the few bits using DirectFB. An interesting issue we had was that even though a proper cursor theme was installed and made the default, we only had a black cross as X pointer. That’s where we learnt it’s needed to manually set a cursor for the root window, which can be done this way:

GdkCursor *cursor = gdk_cursor_new(GDK_LEFT_PTR);
gdk_window_set_cursor(gdk_get_default_root_window(), cursor);
gdk_cursor_unref(cursor);

Tweaking gtk2-engines was trivial, just a matter of building against the x11 flavour of Gtk instead of the directfb one. Some substitutions in debian/control and debian/rules, and that was done.

Julien also took care of tweaking console-setup so that keyboard-configuration’s and console-setup-udeb’s postinst scripts call setxkbmap when $DISPLAY is set. Meaning we were able to replace kbd-chooser with console-setup-udeb, leading to a correct setting within X right after having selected the layout!

Reverting d-i’s r61645 (which disabled Gtk-based d-i images) was trivial (although while looking back, it was probably unnecessary), and after having messed around with the packages lists (there’s a lot of local udebs at this point), especially to add some fonts, we managed to get an image which seems to work fine (at least in my VirtualBox environment). I tried Chinese, Japanese, Arabic, and French installations, and all of them seem to work fine (installed systems were bootable after an installation in the selected language) while issues were limited to some rendering or translation glitches, which didn’t seem critical at all.

Next steps

Since there were some iterations, and since the “trial-and-error” approach was chosen, the first goal is to generate clean patches against all modified packages, and make sure a single walk through all packages in a clean chroot is sufficient to generate a working d-i image again.

Once that done, which should probably considered (at least, I hope!) quite a good base already, the idea is to look into the various udebs to see whether there are some parts that could be disabled (maybe introducing a trimmed-down flavour especially for the udeb in some non-flavoured-yet libraries), so as to reduce the size of the resulting image.

In the meanwhile, one can fetch the current hand-built netboot image by browsing http://people.debian.org/~kibi/di-x11/. It’s only available for amd64, and weights 23MB. There’s a sha256sum as well as a detached GPG signature in the same directory.