You are expected to type a character (which names the register) at the prompt Copy rectangle to register:
. When you just hit RET
that provides the event return
for the register name, and that is rejected.
Type, for example, a
, and your problem should be solved. IOW, this is pilot error combined with a UI that is not sufficiently clear.
The relevant code, which reads an input event and tries to interpret it as a character, is register-read-with-preview
, in register.el
. This is the test that leads to the error message:
(if (characterp last-input-event)
last-input-event
(error "Non-character input-event"))
Predicate characterp
returns nil
for event return
.
(setq foo (read-event))
Hit the "Enter" key. That binds foo
to return
.
(characterp foo) ;; Returns nil.