Event handling in R
...because you're catching the timeout error with try() so it has not
effect, and hence the while(TRUE) {} loop keeps running.
Without knowing anything about graphics event handlers per se, here's
an alternative to catch the timeout event:
library("R.utils");
plot(0, 0);
eventEnv <- getGraphicsEventEnv();
setGraphicsEventHandlers(prompt='Test');
q <- NULL;
evalWithTimeout({
q <- getGraphicsEvent();
}, timeout=1);
print(q);
does it. See print(evalWithTimeout) to see what you are doing differently.
My $.02
/Henrik
On Thu, Dec 15, 2011 at 9:49 PM, beetonn <Nicholas.Beeton at utas.edu.au> wrote:
Dear R-helpers,
I've just started playing with getGraphicsEvent() in R, and was wondering if there is a simple way to stop this function waiting for input after a pre-defined time, instead of relying either on a non-NULL value from one of the event handlers or for a user-interrupt for it to halt (as per the R manual).
The only way that I've thought of to make this work is using setTimeLimit to kill the function after a set time - here's a (messy) example:
setTimeLimit(cpu = 1)
plot(0, 0)
eventEnv <- getGraphicsEventEnv()
setGraphicsEventHandlers(prompt = 'Test')
while(TRUE)
{
? err <- try(q <- getGraphicsEvent(), silent=TRUE)
? print(err)
}
# Not run
setTimeLimit(cpu = Inf)
but setTimeLimit doesn't seem to kill getGraphicsEvent() properly, as running this code just ends up with the repeated returned error of "Error in getGraphicsEvent(): recursive use of getGraphicsEvent not supported" instead of the intended "Error: reached CPU time limit" every second.
Is there a way to get around this problem, or a different method to make this work? ?Or should I quit dabbling in things beyond my ken?
Thanks,
Nick
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