Earlier quoted context omitted.
> Missing damage tracking, always painting everything (even when the window is a full 4k monitor), Out of curiosity, what GPU accelerated terminal does this.
+1, no idea. But maybe to add a little bit of context, "damage tracking" means for example, that if there is any ongoing animation (like a spinner), then only a small part of the screen will be re-rendered (with proper vertex-time scissors, so only relevant pixels will be computed). I am not sure if it makes sense in the context of a terminal emulator, but it's certainly a big issue for any non-toy GUI toolkits. GPUs…
Without, even if you only redrew your spinner, your display server ends up having to redraw what might be a full screen 4k window, as well as every intersecting window above and below until an opaque surfaces are hit to stop blending.