I want to do what the base does, but then I want to add some derived stuff.
I tried the following but it did not work: (this function is virtual in AguiWidget)
You were almost there, just one small syntax change.
AguiWidget::onSizeChanged(size);
Close.
Use the scoping operator :: (i.e. AguiWidget::onSizeChanged(size))
::
AguiWidget::onSizeChanged(size)
Change AguiWidget.onSizeChanged(size); to AguiWidget::onSizeChanged(size);.
AguiWidget.onSizeChanged(size);