gtk:button-use-underline (object)

object -- a gtk:button widget
setting -- true if underlines in the text indicate mnemonics

Accessor of the use-underline slot of the gtk:button class. The gtk:button-use-underline function returns whether an embedded underline in the button label indicates a mnemonic. If true, an underline in the text of the button label indicates the next character should be used for the mnemonic accelerator key.