Comment 11 for bug 1297688

poy: one concern about Motif, and I'm not sure how important this will be in practice, is that Motif doesn't support Wayland at all. Major distributions such as Fedora [1] are aggressively trying to get Wayland to be the default windowing system. Within a couple of years X11's going to become a compatibility layer on both Fedora [1] and Ubuntu [2]. I wouldn't push back too strongly against an X11-only Linux solution, though: broadly available X11 support won't disappear in the next few years.

Also, someone actually is looking at implementing Motif on Wayland [3], but it began as an unexpectedly serious April Fools joke [4], so I don't anticipate much.

arne: j2c in general & SWT are indeed intriguing. From what I've read, SWT has a lot of advantages and is a more precisely targeted GUI toolkit than the eveything-compatibility-layer of Qt. You're not the only one with that idea, either: http://www.pure-native.com/swtcpp/ is a commercial version and http://nativeswt.sourceforge.net/ is a now-abandoned open source version.

Regarding Qt, most of what you say still applies. It still depends on a MOC to build [5]. It's still somewhat heavyweight (LXDE/LXQt/Razor-Qt developers, for example, found it routinely added 20MB memory consumption to their Gtk+ 2.x to Qt5 ported software). It's still a matter of taste, but Qt seems to have kept targeting about the same niche, so whatever issues you had with it in that regard likely still apply.

[1] http://blogs.gnome.org/uraeus/2013/09/09/fedora-wayland-update/
[2] http://www.omgubuntu.co.uk/2014/03/mir-default-display-server-ubuntu-2016
[3] "Motif on Wayland", https://madhouse.github.io/motifway/
[4] http://asylum.madhouse-project.org/blog/2014/04/01/motif-on-wayland/
[5] http://qt-project.org/doc/qt-5/why-moc.html