The "activate" signal is emitted when the user presses a mouse button while the cursor is over the widget, or hits the Enter key or spacebar while the widget is selected, or if the activate() method has been called from within the program by the widget, or if the activate_item() method has been called from within the program by the widget's parent.

It is also defined as the accelerator signal, so that any accelerator key associated with the widget will also emit the "activate".when pressed, whether the widget is currently selected or not.

On activation, all GtkMenu widgets that are a part of the cascading selection sequence disappear from the screen, regardless of whether or not the GtkMenuItem has its "activate" signal connected to a function within the program.

Callback function

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