GNOME+Kwin: desktops aren't drawn

[Sridhar Dhanapalan]

I've got Kwin set as my window manager in GNOME (I prefer it to Metacity and Compiz). This is set in the Session Manager (System > Preferences > Sessions), where I add an item that executes "kwin --replace" and disable Metacity/Compiz from loading.

I've got multiple desktops set up via the Kwin settings. On the first desktop, wallpaper and desktop icons are drawn as expected. All the other desktops, however, are completely black with nothing on them.

Tested with Ubuntu 8.10.

[Sridhar Dhanapalan (sridhar)]

I should add that this doesn't happen when using Kwin with KDE.

[Martin Gräßlin (ubuntu-martin-graesslin)]

I'm not totally sure, but I think you have to set the number of desktops with the GNOME pager. The pager is allowed to change the number of desktops and it's possible that GNOME desktop relys on the pager changing the number of desktops. I know that Compiz has some hacks to work with GNOME.

Lubos Lunak blogged about running KWin in different environments. You might want to have a look at it: http://www.kdedevelopers.org/node/3848

[Harald Sitter (apachelogger)]

Hey,

I just did some research on this.

First of all, the GNOME pager-like applet, which shows the virtual desktops, only offers the option to add new "workspaces" when using metacity (possibly also with compiz ... wether or not that is a sensible thing or not, since I would expect that it is possible to get information about the amount of virtual desktops directly from the WM, and also to be able to influence the amount [dbus?]...).
So, setting the amount of desktops only works form within the appropriate KDE control module.

The actual rendering issue is however in GNOME, and not KWin.
Scenario 1:
metacity is default, gets replaced by kwin => shown desktops follow the setting defined in KDE (i.e. the amount KWin actually exposes) and get rendered properly, adding them on-the-fly (via the appropriate KCM) works as expected

Scenario 2:
kwin is default (e.g. through WINDOW_MANAGER environmental variabe) => shown desktops follow the setting defined in KDE but anything but the first desktop is not rendered at all

Scenario 3:
kwin is default, gets replaced by metacity, gets replaced by kwin => see Scenario 1

This leads me to the conclusion that probably GNOME either expects KWin something to do, in order to render the desktops (which would be weird, since GNOME obviously knows about the virtual desktops AKA workspaces, so not having them rendered is everything but sensible) or there is just some flaw within GNOME that prevents the desktops from rendering.

Workaround: invoke metacity and then replace it with kwin (something like gnome-wm&& kwin --replace as start command)

I am bouncing this bug to gnome-session, hoping it is the appropriate package :)

Have a nice day, and thanks for the report.

[Sridhar Dhanapalan (sridhar)]

I have discovered that with compositing (3D effects) turned on, I can see the wallpaper and icons on desktop 1 but the others are just plain black. If I deactivate compositing, I can see the wallpaper on all desktops but the icons are only shown on desktop 1. This is in Ubuntu 9.04.