Decided to try writing a Wayland compositor for fun. Took me a few days to get things going to a video-able state.
This is scrollable tiling, heavily inspired by PaperWM (which I'm still using and very much enjoying). You've got an infinite strip of windows that you can scroll through.
It's also got dynamic workspaces which work like in GNOME Shell (the Correct™ way to do workspaces), but all monitors have workspaces.
The repo is https://github.com/YaLTeR/niri if you want to peek at the code
Added quite a number of things into the compositor since then. It's at the point where I can somewhat-comfortably use it for working or (Wayland-only) gaming sessions.
Today I figured out how to make it run as a proper session, launched from GDM, with systemd integration and all. It even mostly works!
Also finally implemented the ability to take screenshots—this one is from a real session.
Kinda want to try my hand at the screencast portal for OBS. How hard can it be, right? 🙃
Almost done adding touchpad gesture support to Smithay!
Here you can see the pinch zoom/rotate gesture visually in gtk4-demo, then the swipe gesture only in WAYLAND_DEBUG on the right, then the hold gesture by stopping the kinetic scrolling by putting a finger on the touchpad.
After adding dmabuf feedbacks to niri, I stumbled upon an extremely strange performance problem when using overlay planes. One specific animation, with a GTK 4 window open, stutters, but only when going into one direction.
Spent half a day debugging it with Smithay developers. Couldn't crack it yet; for some reason an AMDGPU kernel worker just... takes a while under those specific conditions, causing delayed frames. Seems to be doing the same thing as in the normal case, just... slower somehow.
I'm quite enjoying playing with the Tracy profiler. Turns out when you run the program with sudo, it records a ton of extra useful info, like CPU core scheduling, monitor VSync events, kernel context switches, what your process is blocked on.
I also annotated my compositor with Tracy Frame events for monitor VBlank cycles. I can then set a target FPS in Tracy and instantly see which frames were too slow! Both in the bar at the top, and in the main area highlighted in red.
Dmabuf screencasting is crazy good. Here's a histogram of the screencasting overhead on my 2560×1600@165 screen—the median is 300 microseconds, and the worst across 12,669 frames was just below 1 ms. Most of that time is spent rendering the frame, perhaps something could even be further optimized in Smithay.
And yeah, if you look at the profiling timeline, I zoomed it in such a way that almost the entire width is taken by one frame, that is 6.05 ms long. Most of it is completely empty!
Ivan Molodetskikh
Alice 