It sounds like Dark Mode isn't even fully supported yet in Qt5.12 to me. It's getting better, it sounds like, but still not perfect. And even then, it appears that apps need to be built with the very latest versions of of macOS and Xcode for Dark Mode to just almost work correctly (and only when run on those same newest macOS versions).
For obvious reasons, we can't build Sigil with the very latest Qt, on the very latest version of macOS, targeting only the very latest version of macOS.
|