ItemViews : Checkboxes in headers

Consider a column in a table view that is composed of checkboxes.

It would be nice for the column header to show a checkbox which, when clicked, will change the checked state of all of the checkboxes beneath it.

It could also show the checked state of those checkboxes,
showing a check if all are checked, unchecked if all
are unchecked, and indeterminate if there is a mix of checked and
unchecked.

To do this currently the application needs to return a Pixmap for the
Qt::DecorationRole, with the pixmap being a pixmap constructed using
the drawPrimitive.

It would be nice if this would be supported "out of the box".