Hi,
KWayland is a library that provides convenience wrappers for Wayland
protocols. Usually, when we want to implement some Wayland protocol,
first, we add corresponding wrappers in KWayland and after that we
actually implement the protocol in KWin.
Unfortunately, we made a bad design choice in KWayland. It is common in
KWayland to see abstractions over unstable protocols. We do it in the
name of "don't repeat yourself" principle. This reduces the amount of
duplicated code in KWin, but it also makes much more difficult to extend
KWayland. Abstracting unstable protocols turns out to be really bad when
the next version of an unstable protocol contains big changes, e.g.
xdg-shell-unstable-v5 -> xdg-shell-unstable-v6. Due to the API and ABI
compatibility promises, we can't fix the broken design of those
wrappers. We should not try to abstract over Wayland protocols in the
first place!
We need to fix those wrappers in order to implement the corresponding
protocols properly in KWin (and fix a few bugs).
One option is to make KWayland unstable so we are free to do necessary
changes to fix the wrappers, but it doesn't really go along with the
Frameworks' policies. Another option is to move KWayland somewhere else,
e.g. KWin or Plasma.
Alternatively, we could provide new wrappers and append a suffix to
class names, e.g. "2" or "V2". But I don't like this approach for a
couple of reasons. First, we are going to mix two types of versions in a
single class name, e.g. XdgToplevelV6InterfaceV2, etc. Second, some
protocols are not completely implemented in KWin, so we may still need
to change wrappers in a way that may break API or ABI compatibility.
Arguably, we just don't have to push semi-finished changes, but
implementing everything all at once is a bit difficult and tackling one
problem at a time is much easier.
I'm writing this email to bring problems that we currently have in
KWayland up to discussion and find the way in which we can address them.
For what it's worth the question of moving KWayland out of Frameworks to
somewhere else had been raised before, but the discussion got stalled...
sort of. [1]
Cheers,
Vlad
[1] https://phabricator.kde.org/T11903
