title: How to identify when the current tab is changing in a QTabWidget?
body: <p>I'm using a <code>QTabWidget</code> and I need a way to handle the change of the current tab before it actually happens, and possibly cancel it if certain conditions are met. The <code>QTabWidget::currentChanged</code> signal is received after the current tab has changed, but is there a <code>QTabWidget::currentChanging</code> signal or another way to achieve the behavior I need? </p>