bug#5645: 23.1.92; read-event blocks in batch mode

[Michael Albinus <michael.albinus@gmx.de>]

Chong Yidong <cyd@stupidchicken.com> writes:

> Michael Albinus <michael.albinus@gmx.de> writes:
>
>> Call
>>
>> # emacs -Q --batch --eval '(read-event nil nil 0.1)'
>>
>> It does not return.
>
> This is a technical limitation of batch mode.  Input is acquired via
> getchar(): see kbd_buffer_get_event in keyboard.c.  Unfortunately,
> getchar() blocks until input in submitted on standard input.

I see. In my use case, which has caused this bug report, I am waiting
for D-Bus events. This shall be possible also in batch mode; maybe we
can fix this later.

For the time being (23.2 preparation), I'll document this limitation in
dbus.texi, and I'll avoid asynchronous calls in dbus.el, when
noninteractive is nil.

Best regards, Michael.