Having some kind of access control list or other method of enforcing access rights for windows and clipboards is definitely a good thing.
However, such a thing could be relatively easily added to X11 without changing the X protocol, so this does not appear as a sufficient motivation for the existence of Wayland.
I have not tried Wayland yet, because I have never heard anyone describing an important enough advantage of Wayland, while it definitely has disadvantages, like not being network transparent, which is an X11 feature that I use.
Therefore, I do not know which is the truth, but from the complaints that I have heard the problem seems to be that in Wayland it is not simple to control the access rights to windows and clipboards.
Yes, access to those must be restricted, but it must be very easy for users to specify when to share windows with someone else or between their own applications. The complaints about Wayland indicate that this mechanism of how to allow sharing has not been thought well. It should have been something as easy as clicking a set of windows to specify something like the first being allowed to access the others, or like each of them being able to access all the others.
This should have been a major consideration when designing access control and it appears that a lot of such essential requirements have been overlooked when Wayland was designed and they had to be patched somehow later, which does not inspire confidence in the quality of the design.
Having a medium understanding of graphics hardware and software stack, and being an everyday desktop Linux user recently, it's hard to square these kinds of complaints with the actual technical situation. Like, people say X11 is network transparent but that's not in practice true. People argue the same problems could be solved in X11, but in practice despite a decade + of complaining about Wayland nobody did the work make the improvements to X. Unlike say the systemd situation Wayland just seems like a better and necessary design?
At a higher level, I've never found someone who is deeply familiar with the Linux GUI software stack who also thinks Wayland is the wrong path, while subjectively as a user most or all of my Linux GUI machines are using Wayland and there's no noticeable difference.
From an app dev perspective, I have a small app I maintain that runs on Mac and Linux with GPU acceleration and at no point did I need to a make any choices related to Wayland vs X.
So, overall, the case that Wayland has some grave technical or strategic flaws just don't pass the smell test. Maybe I'm missing something?
That means that I can run a program, e.g. Firefox, either on my PC or on one of my servers, and I see the same Firefox windows on my display and I am able to use Firefox in the same way, regardless if I run it locally or on a server.
The same with any other program. I cannot do the same with Wayland, which can display only the output of programs that are running on my PC.
This an example of a feature that is irrelevant for those who have a single computer, but there are enough users with multiple computers, for which Wayland is not good enough.
Wayland was designed to satisfy only the needs of a subset of the Linux users. This would have been completely fine, except that now many Linux distributions evolve in a direction where they attempt to force Wayland on everybody, both on those for which Wayland is good enough and on those for which Wayland is not good enough.
I have already passed through a traumatic experience when a gang of incompetents have captured an essential open-source project and they have removed all the features that made that project useful and then they have forced their ideas of what the application should do upon the users. That happened when KDE 3.5 was replaced by KDE 4.
After a disastrous testing of KDE 4 (disastrous not due to bugs but due to intentional design choices incompatible with my needs), I reverted to KDE 3.5 for a couple of years, until the friction needed to keep it has become so great that I was forced to switch to XFCE. At least at that time there was an alternative.
Now, Wayland does not have an alternative, despite not being adequate for everybody. For now, X11 works fine, but since it seems unlikely that Wayland will ever be suitable for me, I am evaluating whether I should maintain a fork of X11 for myself or write a replacement containing only the functionality that I need. That would not be so complex as there are many features of X11 or Wayland that I do not use, so implementing only what I really need might be simple enough. The main application that I do not control would be an Internet browser, like Firefox or Chromium, but that I could run in a VM with Wayland, which would be preferable for security anyway.
In practice for some applications, for my purposes X11 forwarding never really worked (due to GLX and bandwidth among other issues). So that's 50/50 anecdote. I just checked and it appears Wayland adoption has helped push apps to adopt EGL which helps. There are tradeoffs both ways but let's not pretend X11 is adequate for everyone or every application. Subjectively, when I use Gnome now it's by far better than any version of desktop Linux I used a decade or two ago.
I use X over SSH all the time. And as a fun aside, i can run an ancient Linux distro on my 386, and it can use a modern machine as its X display! Not useful, but cool. I've actually done this with modern SBCs as well, and i don't think there's any way to replicate this on Wayland.
Window positioning API seems like the biggest oversight to me, as someone developing a multi window desktop app at work. That and global hotkeys and accessibility.
Due to my reliance on X over SSH i only run Wayland where i strictly need it (my HDR display, namely)
> Like, people say X11 is network transparent but that's not in practice true
Not done it for a while, but ssh into remote machine and start a GUI app used to work for me. It needs one setting in ssh config AFAIK.
> subjectively as a user most or all of my Linux GUI machines are using Wayland and there's no noticeable difference.
Not anymore. There used to be though, and i think it may have got a bad name by being rolled out by distros (especially as the default) before it was ready for most users. I can remember several issues, the worst was with screenshots.
I can accept that as I use a rolling release distro as a daily driver, so you expect some issues, but its not OK if those rough edges hit people using more mainstream distros (which I think they did)
I have used X11 over WAN and it worked fine. Even connecting to a different country, which a significantly slower connection than I have now.
I do not know the current state of RDP etc., but does it allow you to open a single application rather than an entire desktop on Linux, and does it display correctly for the device you are using rather than the one the app is running on?
Only certain Linux RDP clients support per-app windows and I'm not sure how to actually set that up on Linux (only used WinBoat which is a Windows host and does all the Linux config automatically)
> preventing apps from having unrestricted access to screen contents and clipboard
My question was "How often has that been a problem. Is it a vulnerability that has been, or or likely to be, exploited in practice?
I would have thought that filesystem access is the biggest issue, followed by network access. There are solutions for these, of course, but in most cases the default is either unrestricted or what the app asked for.