Add custom class init and instance init functions [glibmm-2-58]
Custom widget implementations should be able to contain code that is executed in
the class init function or the instance init function. E.g. gtk_widget_class_set_css_name()
can only be called in the class init function, and gtk_widget_set_has_window()
should only be called in the instance init function.
This is now possible in the newest ABI-breaking releases in the master branch,
at the moment with the ABI name gtkmm-2.60
. It would be fine to have this
possibility also without breaking the ABI of glibmm-2.4
.
This issue is also discussed in gtkmm#17 (closed).