If characters in @str are preceded by an underscore, they are underlined
indicating that they represent a keyboard accelerator called a mnemonic.
The mnemonic key can be used to activate another widget, chosen
automatically, or explicitly using [method@Gtk.Label.set_mnemonic_widget].
Sets the label’s text from the string @str.
If characters in @str are preceded by an underscore, they are underlined indicating that they represent a keyboard accelerator called a mnemonic. The mnemonic key can be used to activate another widget, chosen automatically, or explicitly using [method@Gtk.Label.set_mnemonic_widget].