The accessor for the
ignore-hidden slot gets or sets
whether unmapped widgets should be ignored when calculating the size.
Warning
This function has been deprecated since version 3.22 and should not be used
in newly written code. Measuring the size of hidden widgets has not worked
reliably for a long time. In most cases, they will report a size of 0
nowadays, and thus, their size will not affect the other size group members.
In effect, size groups will always operate as if this property was
true. Use a
gtk:stack widget instead to hide widgets while
still having their size taken into account.