[R-SIG-Mac] Sys.sleep() in R.app can't be interrupted

[Duncan Murdoch]

This might be a well known issue, but I couldn't spot it in the FAQ or 
bug list or mailing list archives.

If you execute Sys.sleep(60) in R.app, the command can't be interrupted 
by ESC or Cmd-C until it is done.  R.app becomes completely unresponsive.

The number 60 isn't important, as far as I can tell this is true for any 
sleep time.

A simple workaround is to limit the duration of Sys.sleep() calls, e.g. 
using a function like this:

  Sleep <- function(duration) {
   seconds <- floor(duration)
   for (i in seq_len(seconds))
     Sys.sleep(1)
   Sys.sleep(duration - seconds)
  }

R.app handles interrupts every time Sys.sleep returns, so this means the 
biggest delay is 1 second.

In case this isn't universal, here's my session info:

```
R version 4.5.3 (2026-03-11)
Platform: aarch64-apple-darwin20
Running under: macOS Sequoia 15.7.4

Matrix products: default
BLAS: 
/Library/Frameworks/R.framework/Versions/4.5-arm64/Resources/lib/libRblas.0.dylib 

LAPACK: 
/Library/Frameworks/R.framework/Versions/4.5-arm64/Resources/lib/libRlapack.dylib; 
  LAPACK version 3.12.1

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

time zone: America/Toronto
tzcode source: internal

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

loaded via a namespace (and not attached):
[1] compiler_4.5.3
```

Duncan Murdoch