QAbstractSpinBox: improve documentation

QAbstractSpinBox is a superclass not meant to use directly, but to subclass. But the documentation doesn’t explain how to subclass it properly and gives no examples. Subclassing it for long long value was fairly easy. But how do I do it for a complicated data type when I want to store the inner value and have it updated at the right time?

Example of vague documentation:

>void QAbstractSpinBox::interpretText()
>This function interprets the text of the spin box. If the value has changed since last interpretation it will emit signals.

Emit what signals?

Please make a clear documentation for this class and proper complex subclassing tutorial.