Adding QWidget to layout of other QWidget without reparenting

[Joel Bodenmann]

I'm writing an application that allows loading plugins. Each plugin has to manage it's own settings, however, I'd still like to have a global location where I can change the settings of the plugins:

In the screenshot above, each widget is able to populate the Plugin Settings group box in the bottom right hand corner.

To do that, the plugin interface contains the following methods:

class Plugin
{
public:
    virtual ~Plugin() {}

    virtual QWidget* settingsWidget() = 0;
    virtual void settingsApply() = 0;
};

When a plugin is selected in the list box (left side in the screenshot) I simply delete all items from the groupbox layout and add Plugin::settingsWidget() to it. The problem is that when the preferences dialog closes the groubox and the layout are destroyed and the widget that was returned by Plugin::settingsWidget() gets destroyed too.

The obvious solution to this is to make Plugin::settingsWidget() always return a new QWidget instance. However, I'd like to avoid that for two reasons: Firstly, the returned widget holds a reference to the settings data for that plugin. If Plugin::settingsWidget() gets called multiple times this becomes an issue. Secondly, as you can see there's a Plugins::settingsApply() function which is called when the preferences dialog is accepted(). The plugin MUST save it's own settings, therefore, it must have the ownership of the settings widget.

Long story short: I need to be able to add a QWidget to my preferences dialog without changing the parent/ownership of the widget.
Any ideas or recommendations? Maybe I miss an obvious solution to this problem...

[Chris Kawa]

Well no, you can't have a child that is not a child ;)
Focus, painting and event propagation would be impossible if that was the case.

A simple fix is to set the parent back to null when you no longer need the widget e.g. after you call settingsApply().

[Joel Bodenmann]

@Chris-Kawa said:

A simple fix is to set the parent back to null when you no longer need the widget e.g. after you call settingsApply().

Well that gets the job done. I was wondering whether there was a better / proper solution to this.

Thank you for your help! I appreciate it a lot!