Review Request 114895: Guard against null QX11Info::connection()

[Martin Gräßlin]

> On Jan. 7, 2014, 3:14 p.m., Martin Gräßlin wrote:
> > checking obviously makes sense, though it shouldn't be needed. There must be something else which is wrong here, too.
> > 
> > Could you try what the value of WId is in these cases? I wouldn't be surprised if it were 0.
> > 
> > Oh and that code has unit tests, so I would appreciate if you extend the tests for that case.
> 
> David Edmundson wrote:
>     WId seems to be valid. If I check the dialog with xwininfo before closing plasmoidviewer it shows the same ID.
>     
>     Here is a full backtrace of it being needed: http://pastebin.kde.org/pxjhgw95d
>     
>     I can guard against it inside plasma with 
>     if (!QApplication::closingDown()) around the KWindowEffects calls.
>     
>     I changed to guarding in the library as I can imagine others hitting it in the future and in general library code shouldn't crash on reasonable inputs.
>     
>     
>     
>
> 
> Martin Gräßlin wrote:
>     The backtrace includes QWindow::destroy which as the name says will do an xcb_destroy_window. After that the DialogProxy::onVisibleChanged will be invoked. At that point the window doesn't exist any more so the X calls are just wrong. I'd say this needs fixing in DialogProxy to not call the X specific calls for a destroyed window.
>     
>     Then one could think about whether invoking the methods without a valid xcb_connection is supposed to work. I'd say we should add asserts there instead of the null checks. What do you think?

I just had a look at the QWindow implementation and whether it could provide us a useable way to figure out whether there is a window at all. Unfortunately it doesn't. So ShipIt!


- Martin


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On Jan. 7, 2014, 2:57 p.m., David Edmundson wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://git.reviewboard.kde.org/r/114895/
> -----------------------------------------------------------
> 
> (Updated Jan. 7, 2014, 2:57 p.m.)
> 
> 
> Review request for KDE Frameworks, Martin Gräßlin and Marco Martin.
> 
> 
> Repository: kwindowsystem
> 
> 
> Description
> -------
> 
> Guard against null QX11Info::connection()
> 
> This can fail if the application is currently shutting down,
> this is currently causing a crash on closing plasma with dialogs
> open.
> 
> 
> Diffs
> -----
> 
>   src/kwindoweffects_x11.cpp 72cbb71 
> 
> Diff: https://git.reviewboard.kde.org/r/114895/diff/
> 
> 
> Testing
> -------
> 
> Opened plasmoidviewer -a org.kde.example.widgetgallery expanded the applet, then closed plasmoidviewer
> It used to crash, now it doesn't.
> 
> 
> Thanks,
> 
> David Edmundson
> 
>

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