alt Hacker NewsXdamage isn’t a thing if you’re using a compositor for what it’s worth. It’s more expensive to try to incrementally render than to just render the entire scene (for a GPU anyway).
And regardless, the HW path still involves copying the entire frame buffer - it’s literally in the name.
Thats not true. I wrote a compositor based on xcompmgr, and there damage was widely used. It's true that it's basically pointless to do damage tracking for the final pass on gl, but damage was still useful to figure out which windows required new blurs and updated glows.