(*) make all the methods that require an external mutex take a std::unique_lock as a parameter, so that call sites cannot forget (*) make the forEach method drop the lock when firing listener methods, to reduce the odds of deadlock Change-Id: I0a80e3b3d1c1c03b7de4a658d31fcc2847690903 Reviewed-on: https://gerrit.libreoffice.org/c/core/+/128415 Tested-by: Jenkins Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>