I am not sure this is a bug or not, but xnviewmp and the gimp do not play well together. There are bug reports that go back years on the gimp bug trackers, but tracking down the exact problem has been elusive. Just recently a connection was made between these 2 programs which I can reproduce myself.
With both xnviewmp and gimp open at the same time, make a selection in gimp on a largish (2000x2000px?) image and copy to clipboard.
Gimp will crash.
Close xnviewmp and repeat
Everything works as expected.
Unfortunately I am not savvy enough to troubleshoot this further in any meaningful way, but maybe these 2 programs are sharing a resource somehow? All I know is these 2 programs are the best of their kind and work hand in hand for anyone who does a lot of graphics work. I really hope that both sides will work to resolve this. I'm happy to follow any instruction to help troubleshoot this further.
My Setup:
Arch Linux: 4.18.7-arch1-1-ARCH
XnView MP Linux Version 0.92 64bits (Sep 18 2018)
GIMP 2.10.6
Bug on Gnome site:
https://gitlab.gnome.org/GNOME/gimp/issues/1943
xnviewmp crashes gimp
Moderators: XnTriq, helmut, xnview
xnviewmp crashes gimp
Arch Linux
XnView MP
XnView MP