[R] Argument visible of addTaskCallback

[Duncan Temple Lang]

Hi Eric.

  It appears that the visible flag is being unset in the act of
printing.  So the internal R variable (R_Visible) which is being
reported in the task callback is off/False, even though the object is
being printed.

  I'll add a snippet of code to handle this and report the value of
R_Visible as it is before the printing is called. That should
help avoid the confusion.

  We could call the task callbacks before printing and have them
"vote"/indicate whether to cancel the printing. But I have a more
general mechanism in mind for setting different output "filters".

 D.



Eric Lecoutre wrote:
> 
> Hello,
> 
> I have a question about addTaskCallback
> 
> It is said that the argument visible allows to know wether the result of 
> the top-level evaluation was printed or not.
> 
> Nevertheless, in the following example, I encountered a problem, as it 
> seems not all printed objects are visible...
> 
> Could someone tell me where is the tip?
> 
> TIA
> 
> 
> -----------------------------------------------------------------------------
> SimpleTask <- function()	{
> 	function(expr,value,ok,visible){
> 		print(visible)
> 		return(TRUE)  }		}
> 	
>  > addTaskCallback(SimpleTask())
> 
>  > x<-rnorm(10)
> 	[ Visible= FALSE]
>  > x
> 	[ Visible= TRUE]
>  > summary(x)
> 	[ Visible= FALSE] !!
> -----------------------------------------------------------------------------
> 
> Eric Lecoutre
> 
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-- 
_______________________________________________________________

Duncan Temple Lang                duncan at research.bell-labs.com
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