Excellent writeup, thanks for posting. I was involved with efforts to achieve similar things in Windows (Direct Composition, etc.). In practice, it was enlightening to debug various apps and frameworks and discover just how long repainting can take and how many edge cases there are around slow apps, hung apps, and so on. Who knows, maybe someone there still has some of the malicious test apps I wrote (using the language of this article, apps which acknowledge the sync request and then take multiple seconds to actually paint, etc., etc.).<p>It's definitely a hard problem space that's basically incompatible with how most GUI apps and frameworks worked from 1985-2015.
For me, the quickest way to tell that I'm running on Wayland is seeing if multi-lingual keyboard input is broken. I have right-alt-while-pressed set to switch to a Greek layout (because who doesn't math?), and it reliably works on X11 but breaks in all sorts of weird ways under Wayland (sometimes it simply fails to enable/disable, sometimes it shows a notification as if it changed but switches back when input actually happens, ...).<p>On the bright side I'm finally learning how Vim's digraphs work.
Huge respect to any dev who goes out of their way to fix flickering/glitching/black regions when resizing or moving windows, I honestly can't stand it when I see it because I know it can be solved with effort.
Hoping this makes Xwayland Emacs much smoother to resize. It currently resizes at 0.5 fps for me on KDE.<p>If you're wondering why I don't use the native Wayland build of Emacs, it's because it is <i>massively</i> more laggy on HiDPI screens than the X11 version. I reported the issue upstream, probably won't be fixed for a decade when they'll decide to port to GTK4 and its hardware accelerated rendering backend. It took me a long while to notice that the typing lag I was experiencing was not because of native compilation or single-threading, but pgtk being a bit weak at rendering 3840x2160 pixels at 60 fps. In fact, it was not until I tried the Xwayland build that I experienced how much faster Emacs can feel.
I like to run xeyes and see if they move when I interact with the test application. It's not better but they're as charming as they always were.<p>Also consider running an xwayland app under gamescope which smooths out some issues.
Nice results. It's kind of wild that the "before" behavior would be considered acceptable/shippable by anyone. That kind of jank should be a show stopper.
Hmm. Even with the fix it didn't look very smooth even if it is a lot better. I wonder if that is due to the recording, or due to the mouse settings (mouse poll rate and acceleration settings are very impactful on smoothness), due to X or the toolkit, or due to it not being as good as it can be.