[Qt-interest] Events

[Malyushytsky, Alex]

>>if I have many child objects with many QPushButtons each, do I have to install the event filter for each of them?
And if I don't have an access to the widget (or don't have a rights to change the code) how can deal then?
There should be other way (I hope).

void QObject::installEventFilter ( QObject * filterObj )
does not require you to change the code of existing widget.
The only thing you need is to get a pointer to QObject (QWidget) of each child.

You don't have to list children manually, check the following function
const QObjectList & QObject::children () const

together with QObject::isWidgetType () you can simply iterate through children and install event filter you need on them.

Hope this helps,
    Alex



From: qt-interest-bounces at trolltech.com [mailto:qt-interest-bounces at trolltech.com] On Behalf Of OS Prog
Sent: Sunday, May 02, 2010 6:53 AM
To: qt-interest at trolltech.com
Subject: Re: [Qt-interest] Events

OS Prog wrote:
> Hi,
>
> I'm trying to disable the mouse events to QWidget and its child widgets
> and to replace them with my custom event.
> I have event() function in my parent class and I'm receiving my custom
> events there. After decoding them I'm trying to prepare QMouseEvend and
> send it to the widgets, but their child widget doesn't receive it... I'm
> kind of lost with the events.
>
> I'll try to post some code later.
>
> Regards,
> Nikolay

Nokolay,
IIRC,
Events are send to the widget that has focus (for keyboard), or the mouse is over (for mouse events).

If widget-class is not interested in an QEvent in MyWidget::Event()  then it should call
Event() in its parent class. If the event makes it upto QWidget::Event() (ie no-one is interested in it),
then the event is then sent to the parent (containing) widget of MyWidget.

Therefore, you can't block a child from receiving an event this way.

However, by using the following code, a widget can monitor (and block) any
events sent to another widget.
Here, the containing widget is monitoring its child, but they
don't have to be related.

MyParentWidget::MyParentWidget(...)
{
   QWidget *myChild = ....;

   myChild->installEventFilter(this);

   .....
}

MyParentWidget::eventFilter(QObject *o, QEvent*e)
{
   cout << "Object " << o << " received event " << e->type() << ", blocking." << endl;
   return TRUE;  // TRUE blocks the event, FALSE allows 'o' to see the event.
}


HTH,
Colin S. Miller
Hi Colin,

If I have many child objects with many QPushButtons each, do I have to install the event filter for each of them?
And if I don't have an access to the widget (or don't have a rights to change the code) how can deal then?
There should be other way (I hope).

Other case - if I emulate QMouseEvents, how can I pass them to the child widgets (QWidget with QPushButtons) ?

Regards,
Nik


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