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    #1

    Alt-Tab Box Switch crashes KWin

    (Aside - I'm pretty new to the forums. Do you like new member introduction posts, and if so, where? ... And if not, hi! )

    I've dabbled with Kubuntu for a few releases but only seriously got stuck into it since ~ 1 Dec. I love it - but there are some serious little issue I need help fixing. Here's one:


    Very often, when I hit alt-tab and release it quickly, to go back to the last-used window, KWin crashes on me. This is annoying (but KWin manages to restart in a few seconds as if nothing had happened, which is quite impressive).

    I have Meta-Tab set to use the present windows switcher and this works flawlessly. But I prefer the box switcher for quick use.

    I get a Crash Handler window (and KWin restarts automatically).
    Executable: kwin PID: ... Signal: Segmentation fault (11)
    Unfortunately, it says "The generated crash information is probably not useful" no matter how many times I've tried to Install Debug Symbols. The list of files link says I need debug info for /usr/bin/kwin and /usr/lib/kde4/libkdeinit/libkdeinit4_kwin.so.

    Q - how can I install the necessary debug info?

    If I go ahead and try to report it, it says bugs Bug 260365 - KWin crashes frequently on alt-tab and Bug 245193 - carsh after alt+tab and Bug 237345 - Crash in KWin::TabBox::ClientModel::data are possible matches, the first two being duplicates of the last one.

    Q - should I go ahead and add mine? I don't understand half of what's in those bug reports. How do I know if I should report this to KDE or Kubuntu/Launchpad?

    thanks for any guidance - Joe


    Relevant settings:
    Window Behaviour: Task Switcher: list windows current desktop, sort order recently used, highlight selected window, show outline
    Main: Effect = Box Switch
    Alternative: Effect = Present Windows
    Shortcuts and Gestures: Global Keyboard Shortcuts: Walk through windows = Alt-Tab; Walk through windows (alternate) = Meta-Tab
    Desktop Effects: window switching = Box Switch

    Kubuntu 11.10 Oneiric
    Qt: 4.7.4
    KDE Development Platform: 4.7.3 (4.7.3)
    Desktop theme: Air; Window decorations: Oxygen; Widget style: Oxygen; colours mostly default

    I'd rather be locked out than locked in.
    Tags: None
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    #2
    Re: Alt-Tab Box Switch crashes KWin

    Odd/undesirable behavior can often be linked to video graphics cards/drivers, and you haven't told us anything about what make/model/version of GPU you have.

    However, one quick think to check is if you have the Desktop Blur effect enabled. If you do, try disabling it and see if things don't improve.
    Windows no longer obstructs my view.
    Using Kubuntu Linux since March 23, 2007.
    "It is a capital mistake to theorize before one has data." - Sherlock Holmes​
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      #3
      Re: Alt-Tab Box Switch crashes KWin

      It's NVIDIA ...

      VGA compatible controller: nVidia Corporation GT216 [GeForce GT 320M] (rev a2)

      and I'm running the proprietary driver nvidia-current Version: 280.13-0ubuntu6

      Do you think I should abandon that driver? I can't now remember why I installed it instead of nouveau.
      I'd rather be locked out than locked in.
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        #4
        Re: Alt-Tab Box Switch crashes KWin

        Install newest drivers and see if crash still happens (post-release one from Additional Drivers).
        Plasma 5 look&feel for KDE4: http://kde-look.org/content/show.php...content=166438
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          #5
          Re: Alt-Tab Box Switch crashes KWin

          I updated to nvidia-current-updates (via Additional Drivers) - unfortunately the crash has occurred again.

          I'm now running with Blur turned off (for testing purposes only ... I like blur!)
          I'd rather be locked out than locked in.
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            #6
            Re: Alt-Tab Box Switch crashes KWin

            Meanwhile, should I be worried that I can't get a "useful" bug report for this?

            I get the usual "The generated crash information is probably not useful", but when I click Install debug symbols it thinks for a while and responds "Could not find debug symbol packages for this application." Surely debug symbols for KWin must be available.
            I'd rather be locked out than locked in.
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              #7
              Re: Alt-Tab Box Switch crashes KWin

              No. Not every package has debug symbols, and the 'generic' set doesn't always suffice. It is what it is. :P
              Windows no longer obstructs my view.
              Using Kubuntu Linux since March 23, 2007.
              "It is a capital mistake to theorize before one has data." - Sherlock Holmes​
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                #8
                Re: Alt-Tab Box Switch crashes KWin

                Originally posted by SecretCode
                I'm now running with Blur turned off (for testing purposes only ... I like blur!)
                Blur can be a bit of a CPU hog and also increase heat generation. Using the top utility, check the CPU usage of KWin with blur enabled and compare to the usage with blur disabled. Also observe the changes in heat production and how often your fan runs. I'm more than happy to give up blur in exchange for lower overall CPU utilization and much quieter fans on my ThinkPad T420 with nVidia 3100M.
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                  #9
                  Re: Alt-Tab Box Switch crashes KWin

                  I have almost never seen kwin using a lot of CPU. Firefox yes plasma-desktop sometimes; dbus-daemon and knotify4 sometimes. Not a scientific analysis, but I do quite often look at top or htop or System Activity.

                  Process 'Xorg' does use quite a lot of CPU. Would KWin settings affect that significantly?
                  I'd rather be locked out than locked in.
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                    #10
                    Re: Alt-Tab Box Switch crashes KWin

                    It could be dependent on one's graphics card and other settings like OpenGL. I notice a greater difference on my Acer with Intel Mobile Graphics 4 than I do on my ThinkPad with nVidia 3100M.
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