XnView Software

update:
"FIXED"
I nuked the entire xnviewmp folder in .config.
Now it works. (I just have to re-do all my settings...)
Perhaps an older setting was in conflict with a newer version of xnviewmp.

I tried using both packages in the AUR (standard and system-libs) both have the white rectangle.
fwiw, launching from console spews this:
MDK 0.15.0 (git e8c668a) - Multimedia Development Kit. Copyright (c) 2016-2022 WangBin(QtAV author) <wbsecg1 at gmail.com>
Build for: Linux x86_64; Clang14.0.6 ...

yes, size changes every so slightly on the x axis mostly. ( i assume this is just adjustment from the RGB values of low range to high range going from 0,0,0 to 255, 255, 255 (wider) But I don't know. I don't consider this (the rectangle size) a bug, just reporting what ever I can, so I can find a ...

Is your screenshot showing Help > About a composite image??

Yes. I noted this in the Edited part of my original post. Just to show the information.

Using Linux, Arch XFCE 4.18. I cannot find anywhere to adjust colors that affects SCI.
Noted: It seems to change size as I move the cursor over pixels. As if it is white text on white background.
See attached image. (edited: "about screen" pasted in)