[quotemstr]

> the mouse pointer being affected by heavy load of any kind on the GPU/UI thread.

It's because of stuff like this that we should treat UIs more like real time systems. There's really no good reason at all that a modern machine can't render every frame perfectly every time regardless of system load --- it's due to inadequate attention paid to isolating real-time-ish paths like mouse cursor movement, composition, input event dispatch, and so on from app-induced loads that we get weird responsiveness issues. X actually did a better job in this particular respect than your typical Wayland compositor --- it used interrupt driven mouse cursor rendering, for example.