GtkWidget::set_sensitive
Use this function to toggle whether or not the user can interact with a widget. Setting it to false sets the widget's state to GTK_STATE_INSENSITIVE, which 'greys out' the widget.
You might use this if, for instance, you wanted to prevent a button from being pressed in certain situations.
Setting a container as 'insensitive' will make all that container's children insensitive too.
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