[badsectoracula]

About (1), Linux itself actually does go out of its way to provide stable ABIs as do some very common infrastructure-level libraries like the GNU C libraries. X11 itself is also very stable and both code and the protocol has been compatible going back to the early 90s.

However everything built on top of those is not and does not care about ABI or even API stability and now several desktop projects are actively undermining X11's stability with Wayland. Gtk+ breaks its API and ABI every major version as does Qt - and IMO even if Qt wanted to remain stable, as a C++ library it is very hard to do. Also Qt is really middleware and its developers have very different priorities than what you'd need for an actual platform (not to mention how intentionally misleading they have been towards users of their library).

There is a stable desktop API on Linux, Motif, but that is ugly and nothing targets it anymore and the company behind it nowadays actively promotes Qt instead.

[dkabhina]

Regarding Gtk's frequent breakages, I really can't understand the thought process of whoever is making these decisions.

Gtk is pretty much only relevant on Linux, the Linux desktop is itself a tiny fraction of the desktop market, and the amount of developers who're willing to write GUI apps for Linux, to write documentation or tutorials on the subject, etc. is already extremely low. So you'd think it makes sense to keep things as stable as possible, to make sure that no unnecessary effort is wasted and to encourage people to improve their apps or write new ones.

But apparently the Gtk people don't care. So much effort has been wasted due to stability issues, not even talking about the multitude of good-willing people who got burned in the process and just stopped caring about Gtk altogether. It's really a sad state of affair.