While a button pressed on a screen is held, UpdateCatcher checks every tick
whether the laser is still on one of the screen's overlays. It built that list
from s.All().begin() and s.All().end(), but All() returns a std::array by
value: iterators into two different temporaries, which is undefined behaviour.
A clang build of ft-screens got a garbage length, threw std::length_error, and
aborted on the first click, taking KWin and the desktop with it.
A new /dev/input node is root:root 0600 until udev applies GROUP=input. The
scan probed each new node once and marked it seen even when the open failed, so
a node caught in that gap was never opened. Behind a KVM, a switch brings back a
hub of devices at once: on the Frame, four nodes failed with EACCES in one switch,
the keyboard was never grabbed, and its keys went to gamescope instead of the
desktop screens. A node that isn't readable yet now waits for the next scan.
CuriousJ