invalid sizeHint()

Is there any reason why the function sizeHint() should return a invalid QSize?

My code is

Code:

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QTableWidgetItem *header = new QTableWidgetItem("Hello\nWorld");
QSize size = header->sizeHint();

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Are you using a layout? Doesn't look like it, in which case, the QWidget docs state that the function returns an invalid size. QTableWidgetItem::sizeHint() implies that it returns the value from a previous call to setSizeHint().

The problem is that QTableWidgetItem isn't a widget in itself, so it cannot be putted inside a QLayout