[Rd] Could Rstd_Busy do something (src/unix/sys-std.c)?

[Jakson Alves de Aquino]

On Sat, Dec 15, 2012 at 1:09 PM, Simon Urbanek
<simon.urbanek at r-project.org> wrote:
> On Dec 15, 2012, at 6:36 AM, Jakson Alves de Aquino wrote:
>> I could avoid the crash if I knew that R is busy at the moment that
>> it receives the SIGWINCH. Thus my question is: Could Rstd_Busy()
>> set the value of a variable so packages like setwidth could know
>> that R is busy?
>
> You're looking at the wrong spot - the Busy callback is meant for UI
> signaling that R may enter a longer time of processing, it is not
> really an indicator that R is busy - R can be busy even without the
> busy state being signaled.

Thanks for your suggestions!

Although the comment above Rstd_Busy() (at src/unix/sys-std.c) says
"actions during (long) computations", the function is called whenever
any command is entered in R Console.

> But back to your original question - there are a few spots where you
> can process you request : the most obvious one is in the ReadConsole
> callback - that callback doesn't return until the user has entered a
> line - this would be a way to a GUI to handle this.

Both ptr_R_Busy and ptr_R_ReadConsole are declared on Rinterface.h,
but I can't use them because setwidth doesn't provide front-end to R
and Rinterface.h has the following statements:

    This header file is to provide hooks for alternative front-ends,
    e.g. GUIs such as GNOME and Cocoa.  [...] It should not be
    included by package sources unless they are providing such a
    front-end.

> The other way is to register an input handler and signal your FD
> when you get SIGWINCH, that guarantees that your handler will be
> called as soon as possible after the signal has arrived - that is
> probably what you want (see CarbonEL for a simple example how this
> is used).

Based on CarbolEL, I added the following to setwidth_Start() function:

    int fds[2];
    if(pipe(fds))
        Rprintf("pipe > 0\n");
    else
        Rprintf("pipe = 0\n");
    ifd = fds[0];
    ofd = fds[1];
    addInputHandler(R_InputHandlers, ifd, &uih, 32);

And, also based on CarbolEL, I created the following uih() function:

    static void uih(void *data) {
      char buf[16];

      if(read(ifd, buf, 16) == 0){
          Rprintf("read = 0 :: %s\n", buf);
          Rprintf("%d written\n", write(ofd, buf, 16));
      } else {
          Rprintf("read != 0\n");
      }
    }

However, the uih() function never gets called.

Best,

-- 
Jakson Alves de Aquino
Federal University of Ceará
Social Sciences Department
www.lepem.ufc.br/aquino.php