PopupApplet and setFocus() behaviour

[Marco Martin]

On Thursday 13 August 2009, Dmitry Suzdalev wrote:
> Hi guys and girls!
>
> While making some progress on klipper engine+applet I discovered some
> oddities with focus behavior. I hope you can give me some hints about my
> situation (don't get scared by amount of text below, i tried to make it
> simple to follow).

in the microblogging plasmoid the focus to the input field seems to be 
correctly given.
it sets the focus to the input field in the focusIn event of the applet (that 
always happens after a popup event) would be useful to you?

i am wondering if a setMainInputWidget() api call could be added to the 
popupapplet api, if it's a common case enough


> General layout of applet widgets is the following:
>
> Applet is a PopupApplet.
> It has a QGraphicsProxyWidget as graphicsWidget(),
> which has embedded QWidget (named KlipperWidget)
> which has a QListView inside (it displays clipboard history entries).
>
> What I'm trying to do is to make sure that this QListView will always have
> keyboard focus when popup is shown.
>
> I'm doing it by overriding a PopupApplet::popupEvent() and calling
> KlipperWidget's setFocus() function.
> KlipperWidget has a QListView set as a focus proxy for this to work.
>
> And it works... but only when I launch applet in
> "plasmoidviewer -f horizontal klipper".
>
> Problem: When applet is inside plasma-desktop, no focus gets set.
>
> I tried to debug this and found that when running as a part of
> plasma-desktop, QListView actually gets only FocusOut event, and not a
> single FocusIn.
>
> After looking through souces of a popup applet and debugging a bit, i also
> found that probably the following happens when running in plasma-desktop:
>
> 1. PopupApplet::popupEvent() arrives before popup gets WindowActivated
> event 2. I call setFocus()
> 3. Immediately after this eventloop delivers WindowActivated event ( for
> "dialog" widget inside popupapplet.cpp)
> 4. WindowActivated event gets inside a QGraphicsScene, after this scene
> sends FocusOut event to any active focus item inside it
> 5. FocusIn is sent to popupapplet's toplevel dialog, but my widget gets
> only FocusOut
>
> Somehow this doesn't happen for plasmoidviewer. Maybe order of
> Activation/FocusIn event differs there, dunno.
>
> Anyway, if someone has read until here, let me and with a question:
>
> What to do? :-)
>
> It might be a bug somewhere, it might be not. I'm not sure.
> I can't find a mechanism to defer my setFocus() until i know that popup
> dialog has been shown. I don't want to use a timer as that's not 100% fix
> and can lead to users noticing a slight delay.
>
> In the end I want to simply ensure that my widget will always have focus
> when shown in a popup. Is this possible? Is there some potential workaround
> you see?
>
> Thanks in advance,
> Dmitry.
>
> PS. If you want to look at the code it can be found here:
> http://websvn.kde.org/trunk/playground/base/klipper-ng/plasmoid/applet/
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Cheers, 
Marco Martin