[ESS] How to tell if R is ready after ess-eval-*?

[Ulrich Keller]

Dear list members,

maybe I am missing something obvious here, but how can I tell when R is
ready after sending a longer-running command with e.g. ess-eval-line?
For example, if I send this:

Sys.sleep(5)

with ess-eval-line, the minibuffer will immediately say "Finished
evaluation" and the process buffer will show the usual prompt (">").
However, R will not accept input for 5 seconds.

To take very slightly more realistic example, running this:

for(i in 1:1e7) tmp <- sin(i)
for(i in 1:1e7) tmp <- sin(i)

using ess-eval-region results in much the same problem. "Finished
evaluation" appears immediately, and the prompt looks as if R was ready
to accept input, but it isn't.

Rstudio, for example, has a little "stop sign" in its interface that is
greyed out when R is ready, and red when it's running (it can be clicked
to interrupt a running calculation). The same is true, I think, for
Rkward and the Windows R GUI. Is there any way to get something similar
in ESS?

I'm using ESS 5.13 in Emacs 23.3.1 with R 2.12.2 (Arch Linux i686).

Thanks in advance,

Uli