// Valid input. Either there's only 'from' input, or 'from' == 'to'.
// Deactivate OK/Apply if odd/even selection implies no pages.
bool const odd_pages = static_cast<bool>(fl_get_button(dialog_->check_odd_pages));
bool const even_pages = static_cast<bool>(fl_get_button(dialog_->check_even_pages));
bool const odd_only = odd_pages && !even_pages;
bool const even_only = even_pages && !odd_pages;
// Valid input. Either there's only 'from' input, or 'from' == 'to'.
// Deactivate OK/Apply if odd/even selection implies no pages.
bool const odd_pages = static_cast<bool>(fl_get_button(dialog_->check_odd_pages));
bool const even_pages = static_cast<bool>(fl_get_button(dialog_->check_even_pages));
bool const odd_only = odd_pages && !even_pages;
bool const even_only = even_pages && !odd_pages;