Smooth Tasks is creating blank taskbar entries. Here's a screenshot: http://i.imgur.com/zb8iI.png. They don't go away until I restart plasma-desktop. I'm using the latest revision from the KDE 4.7 branch.
Can you say under which circumstances this happens? Is it possible to produce a similar behavior with plasma’s default task bar?
The past few days, I've been trying to come up with an answer to your first question. Unfortunately, I haven't really noticed anything in particular that is causing it. The only thing I have been doing differently since I started noticing this issue is making more use of Activities. I could be wrong, but it seems to mainly happen when I have 2+ Activities running at once... I tried adding the default task manager plasmoid after a blank entry already appeared in Smooth Tasks and it didn't show the blank entry... It might be worth noting that right-clicking on the blank entries produces the Smooth Tasks context menu, *not* the menu that comes up when right-clicking on a real taskbar entry.
Hello. I experienced this issue too. I'm not sure, but the blank entry appeared after a dialog-like window was opened and closed.
I ran eclipse, opened android library manager, launched library donloading. During these steps several dialog windows (with library selection, confirmation, etc.) appeared.
I managed to reproduce this issue.
1. Set the option to show windows only from current desktop
2. open any window
3. switch to another desktop
4. close opened window (i pressed ctrl+f10 to show all windows)
5. return to the desktop where the window was opened and you'll see a blank entry
Fixed in branch kde-4.7 by copying code from the default task plasmoid. Actually, I think it only works around a real bug in libtaskmanager, since smooth-tasks (and the default task bar) gets signals for added items which do not represent a task, group or launcher at all.