send signal from QCombobox

[jpn]

activated and highlighted signals are emitted only when combo box contains items than can be activated or highlighted.

Try this:
Inherit QComboBox and override:

void QWidget::focusInEvent ( QFocusEvent * event )  [virtual protected]

void QWidget::focusInEvent ( QFocusEvent * event )  [virtual protected]

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When the combo box receives focus for the first time (when it's empty), you could emit a signal stating it needs to be populated.