def toggle_pac(self):
        """Enable and disable PAC options."""
        if Pac is not None:
            pac_on = self.pac['pac_on'].get_value()
            self.pac['prep'].setEnabled(pac_on)
            self.pac['box_metric'].setEnabled(pac_on)
            self.pac['box_complex'].setEnabled(pac_on)
            self.pac['box_surro'].setEnabled(pac_on)
            self.pac['box_opts'].setEnabled(pac_on)

            if not pac_on:
                self.pac['prep'].set_value(False)

        if Pac is not None and pac_on:

            pac = self.pac
            hilb_on = pac['hilbert_on'].isChecked()
            wav_on = pac['wavelet_on'].isChecked()
            for button in pac['hilbert'].values():
                button[0].setEnabled(hilb_on)
                if button[1] is not None:
                    button[1].setEnabled(hilb_on)
            pac['wav_width'][0].setEnabled(wav_on)
            pac['wav_width'][1].setEnabled(wav_on)

            if pac['metric'].get_value() in [
                    'Kullback-Leibler Distance',
                    'Heights ratio']:
                pac['nbin'][0].setEnabled(True)
                pac['nbin'][1].setEnabled(True)
            else:
                pac['nbin'][0].setEnabled(False)
                pac['nbin'][1].setEnabled(False)

            if pac['metric'] == 'ndPac':
                for button in pac['surro'].values():
                    button[0].setEnabled(False)
                    if button[1] is not None:
                        button[1].setEnabled(False)
                pac['surro']['pval'][0].setEnabled(True)

            ndpac_on = pac['metric'].get_value() == 'ndPac'
            surro_on = logical_and(pac['surro_method'].get_value() != ''
                                       'No surrogates', not ndpac_on)
            norm_on = pac['surro_norm'].get_value() != 'No normalization'
            blocks_on = 'across time' in pac['surro_method'].get_value()
            pac['surro_method'].setEnabled(not ndpac_on)
            for button in pac['surro'].values():
                button[0].setEnabled(surro_on and norm_on)
                if button[1] is not None:
                    button[1].setEnabled(surro_on and norm_on)
            pac['surro']['nblocks'][0].setEnabled(blocks_on)
            pac['surro']['nblocks'][1].setEnabled(blocks_on)
            if ndpac_on:
                pac['surro_method'].set_value('No surrogates')
                pac['surro']['pval'][0].setEnabled(True)
Enable and disable PAC options.