Creating slots in Designer

When you are editing signals and slots in Designer, there is a possibility to add a custom slot to a widget. What's the point of this operation? How would you "fill in" the code of this slot, since you don't really have access to the source of the widget?

You "fill in" the code of the extra slots when you define the class which uses the designer form.
Using the slots in designer only results in one line of code connecting the widgets (which dosen't require the slots to be implemented because the signal and slot arguments of QObject::connect are just char*).
If you have a QPushButton connecting to a custom slot of your QWidget form this code could look something like this:

Code:

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QObject::connect(neatPushButton, SIGNAL(clicked()), yourForm, SLOT(foo()));

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So you just have to define and implement the slot in the class using the form. (which makes the direct approach pretty pointless; you would have to write a QWidget subclass either way)