Hey Peter,
2008/7/10 Peter Klar <[EMAIL PROTECTED]>:
> so far I understood objects derived from WObject are automatically deleted
> once their parent is deleted (similar to Qt QObjects), e.g.
> new WLabel(parent)
> is automatically deleted once parent is deleted.
>
> When only using
> new WLabel()
> it has to be deleted manually.
That is indeed the case (as in Qt).
> I recognized that when using (nested) layouts at least within a
> WContainerWidget I have to create my WObjects without making it a child of
> the parent WContainerWidget, else I get a warning like
> Warning: WContainerWidget: ignoring twice addWidget!
The warning has been fixed a few days ago in CVS, and the behaviour
has been documented better.
The warning has been changed to read "WContainerWidget::addWidget():
reparenting widget." only if a widget changes parent as result of
adding it to a container. Otherwise, the whole operation is ignored
(which would be in your case).
Thus, you can add the widget to a container immediately. If not, the
layout will do this for you.
> Simplified ctor:
>
> SampleClass::SampleClass(...) : WContainerWidget(...)
> {
> WVBoxLayout* vLayout = new VBoxLayout(this);
> WGridLayout* gridLayout = new WGridLayout();
> WLabel* foobar = new WLabel();
>
> vLayout->addItem(gridLayout);
> gridLayout->addWidget(foobar, 0, 0);
> }
>
> This works fine but I'm unsure whether I have to delete foobar manually.
So, you are find, since the layout will parent the widget itself.
> If I specify 'this' (derived from WContainerWidget) to the WLabel ctor I get
> the above warning message.
Which was a bit confusing, and this behaviour is no longer.
> I just want to be sure whether WObjects added to a WLayout become part of
> the object tree and are automatically deleted.
>
> Also I'm unsure about the WLayouts itself as they don't derive from
> WObject - what's about them in this context?
This has been documented now as well: the container assumes ownership
of the layout (included nested layouts).
Admittedly, the 2.1.4 release, the maiden release for our layout
managers, was indeed a bit confusing with respect to all this. It also
contained some bugs related to the life-cycle of layouts that are
added to a container that has already been rendered, and the behavior
of WContainerWidget::clear() with respect to layouts.
These have all been fixed in CVS.
Regards,
koen
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