Look for a whole column at once so we don't have to iterate all draw objects for every cell, but only once per column. Follow-up for 3a2a430ae8e2c1647c18d8904477949f6e2e7941 Change-Id: Ic8740fca7d595528785b432c1cedf4fad4f13ba1 Reviewed-on: https://gerrit.libreoffice.org/48416 Tested-by: Jenkins <ci@libreoffice.org> Reviewed-by: Eike Rathke <erack@redhat.com>