I know it's unrelated, but erasing smart pointer types perhaps is not the greatest idea. Could you please use concrete type instead of auto while you're on this?

Heh, you could make it a bit simpler:

for (const QRect &rect : region) {
    ...
}

Keep includes sorted please.

The "Almost Always Auto" crowd would disagree with you, but sure, your choice. Done.

Heh indeed. I looked at the API, saw begin/end, used begin/end.... I forgot that this means range-for is available too :)