bug#20445: excessive redisplay / echo area resizing during byte-compilation

[martin rudalics <rudalics@gmx.at>]

 > This is the problem: in order to "not emit a message" this code emits
 > the message and then immediately hides it by emitting "the empty
 > message" on top of it.
 >
 > Since `message' redisplays right away (rather than waiting for the next
 > "idle" moment to perform redisplay, as is the case for normal buffer
 > changes), this result in a lot of wasted work, and it won't truly do
 > what was intended:
 > - If your machine/display is slow enough, you will see it
 > - If your system "prints" messages by speaking them out loud (e.g. with
 >    emacspeak) you will hear them.
 >
 > Why not just do:
 >
 >       (when byte-compile--interactive
 >         (apply #'message format args))
 >
 > ?

But if there are no errors this would not display a message at all with
Glenn's scenario.  IMHO `byte-compile--interactive' puts the cart before
the horse.  Rather, displaying messages should be the default and the
caller should be able to suppress them via a `byte-compile--no-message'
variable or something the like.  So I'd instead use

   (unless byte-compile--no-message
     (apply #'message format args)))

martin