Even though Gtk3 is still riddled with regressions compared to Gtk2, and there's no stable theme interface, and for example the Raleigh theme engine completely broke in 3.20, the GNOME devs seem to have decided to take it to the next level.
That means, unless I'm reading things wrong, this is the gist:
1. API and ABI breakage twice a year
2. Applications that have been linked for 4.2 on a system with 4.2 dev files installed will still run when the system gtk4 is 4.4. But you're not allowed to build a 4.2 app anymore once 4.4 is on the system. This means, the 4.2 .so can exist in parallel but not the development files. Those are allowed to exist for only one gtk4 release.
3. (2) combined with (1) is a nice way to prevent adoption
Now, this may sound rude, but given the state of Gtk3 after 10 major releases and the overall way devs have dealt with the community, I must say I welcome this, because it can be a nice motivator for everyone that still believed in Gtk3 to look at Qt.
* Wireshark has a Qt frontend now
* wxWidgets has a Qt backend now (experimental for now)
* mkvtoolnix is Qt only now
* the list goes on
If anyone believes developers ported from Gtk2 to Qt for fun, please consider the effort it takes.
Yes, gtk2 has limitations, but there was ABI and API stability on all layers. Since gtk3, the development model seems to be inspired by web applications in that breakage is frequent and stability is mostly not guaranteed. It starts with drawing regressions and extends to a theming api which is unstable and therefore could also not exist, because each theme has to exist for each major gtk3 version.
Had Gtk3 only added Wayland and HiDPI support, and kept API stability for the most part, we wouldn't find ourselves in this unfortunate situations. Since, more than a few applications have migrated to Qt.
I don't like some of the things in Qt5 like the file selector, but that's a minor nuisance for avoiding gratuitous regressions.
I have to use Firefox ESR because the switch to Gtk3 broke too much in the UI (in addition to general non-existence of stable Gtk3 themes).
That means, unless I'm reading things wrong, this is the gist:
1. API and ABI breakage twice a year
2. Applications that have been linked for 4.2 on a system with 4.2 dev files installed will still run when the system gtk4 is 4.4. But you're not allowed to build a 4.2 app anymore once 4.4 is on the system. This means, the 4.2 .so can exist in parallel but not the development files. Those are allowed to exist for only one gtk4 release.
3. (2) combined with (1) is a nice way to prevent adoption
Now, this may sound rude, but given the state of Gtk3 after 10 major releases and the overall way devs have dealt with the community, I must say I welcome this, because it can be a nice motivator for everyone that still believed in Gtk3 to look at Qt.
* Wireshark has a Qt frontend now
* wxWidgets has a Qt backend now (experimental for now)
* mkvtoolnix is Qt only now
* the list goes on
If anyone believes developers ported from Gtk2 to Qt for fun, please consider the effort it takes.
Yes, gtk2 has limitations, but there was ABI and API stability on all layers. Since gtk3, the development model seems to be inspired by web applications in that breakage is frequent and stability is mostly not guaranteed. It starts with drawing regressions and extends to a theming api which is unstable and therefore could also not exist, because each theme has to exist for each major gtk3 version.
Had Gtk3 only added Wayland and HiDPI support, and kept API stability for the most part, we wouldn't find ourselves in this unfortunate situations. Since, more than a few applications have migrated to Qt.
I don't like some of the things in Qt5 like the file selector, but that's a minor nuisance for avoiding gratuitous regressions.
I have to use Firefox ESR because the switch to Gtk3 broke too much in the UI (in addition to general non-existence of stable Gtk3 themes).