QTableWidget QTableWidgetItem

[jpn]

There is no colour change to be seen. I can colour any other item in the table this way, but not those from the headers. What do I need to do?

You must either override
QHeaderView::paintSection()or
use a custom style and implement:
QStyle::drawControl(QStyle::CE_Header)

Another thing...
the signal QTableWidget::itemDoubleClicked ( QTableWidgetItem * /*item*/ )
gets called on double click on any cell, except those in the headers.

QHeaderView::sectionDoubleClicked()

PS. Headers are accessible through QTableView::horizontalHeader() and QTableView::verticalHeader()