baseline allocation doesn't work
Baseline allocation appears to be broken in Gtkmm:
Compile and run btest.cpp, open the gtk inspector and turn on show baselines and observe that no baselines have been allocated. The Miscellaneous section in the inspector will also show that no baseline got allocated.
I recreated this minimal test case in C btest.c and baselines get allocated.
Gtkmm version 3.24.2-2, Gtk 3.24.21-1, both from arch linux repositories