Launcher doesn't autohide

Work around:
This article explains the how to set the hide policy:
http://katastrophos.net/andre/blog/2011/04/24/disable-the-auto-hide-functionality-of-ubuntu-unity-2d/

autohide may be
  0 - do not hide
  1 - always hide
  2 - dodge window

I'm able to reproduce this bug (with all i386 daily-lives after 20110618, up to the most recent I have tried: 20110623, with unity-2d/unity-2d-launcher 3.8.8-0ubuntu1 and metacity 1:2.34.0-0ubuntu1), but only on live CD systems, and only in unity-2d sessions that I did not manually log in to. That is, the first session on live CD after selecting Try Ubuntu has this bug, but when I log out and back in, the launcher auto-hides (and auto-unhides) without problems. I have not been able to reproduce this bug on any installed system.

For me, this bug is always accompanied by the initial absence of any application icons in the launcher--at the start of the session, only the Workspaces, Applications, and Files & Folders icons (and the Trash icon at the bottom) are present in the launcher. If no icons are pinned to (bookmarked in) the launcher during the first unity-2d session on the live CD, then all the expected application icons (e.g., Install Ubuntu, Firefox, Software Center, and LibreOffice applications) show up on the second (manually logged in unity-2d session).

It is also accompanied by two more (seemingly interrelated) problems: (1) Moving the mouse pointer to the upper half of the topmost application icon causes the launcher's contents to scroll, so that the icon disappears off the top of the launcher; and (2) when a running application is pinned to the launcher ("Keep In Launcher") and then exited, its icon remains in the launcher but is not always displayed. In both (1) and (2), moving the mouse pointer out of the launcher toggles whether or not the affected icons are displayed (moving it into the launcher has no special result, except to make it possible for it to be moved out of the launcher). In (1) but not (2), clicking in the unoccupied space in the launcher (above Trash and below all other icons) fixes the problem (until next time it is triggered). Like the launcher's failure to hide, all these problems occur only on the live CD, and only in the first unity-2d session after booting.

I booted the same live CD on another exactly identical system (these are VMware Workstation 7.1.4 build-385536 virtual machines on a Natty amd64 host, and they are running the same live CD image). That system also lacks initial application icons. But on the duplicate virtual machine, problem (1) occurs but not problem (2), and moving the mouse pointer out of the launcher produces no change.

On the first of the two virtual machines, bug 801161 occurred. On the second, it did not. Perhaps that (or the resulting restarting of unity-2d) is what made the difference.

On both virtual machines, before pinning any applications to the launcher, gconftool-2 -R /desktop/unity-2d/launcher" produces no output, and after pinning an application to the launcher (in this case, gnome-terminal), it's output is

 favorites = [gnome-terminal.desktop]

with the hide_mode and use_strut keys conspicuously missing. If no icons are pinned to the launcher in the first unity-2d session, then as described above, the second session has all the usual icons; in that case, the second session's gconf2 keys in /desktop/unity-2d/launcher are:

 hide_mode = 2
 favorites = [ubiquity-gtkui...

I don't boot from a liveCD but on my HDD with Ubuntu 11.10. On lightDM, the selected session is Unity but I use the fallback while Unity doesn't work.
Sinse I use Unity 2D on Oneiric I have the problem of a non working autohide. I reinstall the system once, and the but is still present.

In gconf, /desktop/unity-2d/launcher contains only one key, "favorites". I have no hide_mode super_key_enable or use_strut keys. I didn't found any entry for unity-2d in dconf.
Icons are always loaded, and Unity-2D never crash (only metacity sometimes, but because of Wine).

System :
Ubuntu Oneiric Ocelot 64bits
Intell i5 2500k on ASUS P8P67-LE
4Go RAM (3.9 detected by gnome-system-monitor)
linux-image-3.0-1-generic (if I remember well)

@RIVIERE Aurélien
Do you have any of the other problems I listed (application icons not appearing, or appearing and disappearing, or the Unity launcher's contents scrolling so the topmost icon is invisible)?

"On lightDM, the selected session is Unity but I use the fallback while Unity doesn't work.
Sinse I use Unity 2D on Oneiric I have the problem of a non working autohide. "

If you explicitly select "Ubuntu 2D" instead of "Ubuntu" as the session type in the lightdm login screen, do you still experience the unity-2d autohide problem?

No, the whole set of icon is correctly loaded and never disappears, and I have no problems with the launcher except when the first app rises above the panel, or when I have a white strip at the left side of the launcher (easily removable by scrolling the app-shortcuts).

I wondered if it couldn't solve my problem, me too, but when I log me in, I rarely take the time of switch the session. But indeed, set Ubuntu 2D instead of Ubuntu do the launcher hide himself correctly.

This bug was fixed in the package unity-2d - 3.8.10-0ubuntu1

---------------
unity-2d (3.8.10-0ubuntu1) oneiric; urgency=low

  [ Florian Boucault ]
  * debian/unity-2d-launcher.install:
    - do not install launcher/launchermenu.css anylonger as its now shipped as
      part as libunity-2d-private-qml.so using the Qt resource system
  * debian/libunity-2d-private0:
    - move symbolic link to /usr/share/backgrounds/warty-final-ubuntu.png from
      /usr/share/unity-2d/places/artwork to /usr/share/unity-2d
  * debian/control:
    - add pkg-config as a build dependency

  [ Didier Roche ]
  * New upstream release:
    - FTBFS due to erroneous check on libwnck (LP: #800550)
    - [dash] Search is slow and freezes (LP: #774569)
    - Some community lenses do not display anything - UnityHorizontalRenderer
      not implemented (LP: #790319)
    - [underthehood] the ListAggregatorModel class is not unit tested
      (LP: #794482)
    - Missing a GConf schema file for the /desktop/unity-2d/… keys
      (LP: #750303)
    - [dash] home screen search hint should be 'Search' (LP: #797825)
  * debian/unity-2d.gconf-defaults,
    debian/20_ubuntu-2d-gconf-default:
    - transition some gconf keys from session-wide to system-wide
      (LP: #797672, #797676)
  * debian/control:
    - ensure we are still using gtk2 indicator for alpha2 (LP: #804938)
    - bump standards-version
 -- Didier Roche <email address hidden> Mon, 04 Jul 2011 11:05:54 +0200