Gnome 3.22 Wayland is eating my chess pieces (unicode chess font)

[Stefan Salewski <mail ssalewski de>]

Some days ago my Gentoo box finally updated to Gnome 3.22.

First surprise: GtkSourceView ignores Text Scaling settings -- seems to
be a well known bug:
https://bugzilla.redhat.com/show_bug.cgi?id=1382840
Not a real problem, but surprising.

Today I logged in using wayland session, selected by gears menu of GDM
login screen and launched my chess game. I got this:

http://ssalewski.de/tmp/nimchesswayland.png

When I log out and in again with ordinary Gnome X session all is fine
again as in

https://github.com/ngtk3/nim-chess2

The cutoff effect is large for a small window, and decreases for a very
large window. So there seems to be a fixed wrong offset in font glyph
size? I have still no real idea, and I wonder why wayland can make a
difference at all for pango font rendering.

Any ideas?