Qt. QSplitter. Handle double click when cursor is under splitter - c++

Question

I need to handle double click for QSplitter when cursor is under splitter.
I redefined mouseDoubleClickEvent. But this does not work for this case.
When I do doulble click when cursor is under splitter (ready to move splitter) the method is not calling.

Answer 1

You can use an event filter to filter all events going to the handle of Qsplitter :
bool MyClass::eventFilter(QObject * obj, QEvent * event)
{
if(event->type()==QEvent::MouseButtonDblClick)
{
...
}
return false;
}
Also don't forget to install event filter in the constructor of your class :
MyClass::MyClass(QWidget *parent):QWidget(parent)
{
...
ui->splitter->handle(1)->installEventFilter(this);
...
}

Answer 2

I needed the same in order to be able to evenly space the widgets in the splitter when the user double clicks on the handle (this was my use case). Overriding QSplitter.mouseDoubleClickEvent() does not work because it seems that the handle consumes the double click event itself so it is not propagated to the parent QSplitter. The solution proposed in the accepted answer using eventFilter is quite good but is has the disadvantage that it is not 'dynamic', i.e. the event filter is not installed when the user adds new widgets to the splitter during runtime. So we need to find a way to install the event filter dynamically. There are two options to achieve this:
Override QSplitter.addWidget() and QSplitter.insertWidget():
# inside class MySplitter
def addWidget(self, widget):
super(MySplitter, self).addWidget(widget) # call the base class
self.handle(self.count() - 1).installEventFilter(self)
def insertWidget(self, index, widget):
super(MySplitter, self).insertWidget(index, widget) # call the base class
self.handle(index).installEventFilter(self)
but this is a bit problematic when the user adds widgets by not using these two methods but by setting parent to the child widget, though this is discouraged by the docs - see: http://doc.qt.io/qt-5/qsplitter.html#childEvent
Intercept the childEvent(), which feels a bit hacky but is error proof:
# inside class MySplitter
def childEvent(self, event):
if event.added():
# Note that we cannot test isinstance(event.child(), QSplitterHandle)
# because at this moment the child is of type QWidget,
# it is not fully constructed yet.
# So we assume (hacky but it works) that the splitter
# handle is added always as the second child after
# the true child widget.
if len(self.children()) % 2 == 0:
event.child().installEventFilter(self)
super(MySplitter, self).childEvent(event) # call the base class
I am using b) and it works for me quite well. This has the advantage that you do not need to subclass (I do, however, for teh sake of simplicity), you can install another event filter to intercept the childEvent and install the event filter from outside.
Sorry my code is in PyQt, but I think it is idiomatic enough and easily translated to C++.