[R] tcltk and locator interaction

[Denham Robert]

I was trying to write a small routine using the tcltk library which
allows a little bit of interaction with a plot.  Basically, using the
function locator(1), a user could click on an area of a graph which
would cause a little tcltk window to pop up.  When they have finished
with the window, they click on a tcltk button, the window disappears,
allowing the user to select another point on the graph and repeat the
procedure.

This sort of works, but I can't get the tcltk window to disappear in
between mouse clicks, so the user clicks, the window pops up, they press
ok, but the window remains until _after_ a new point has been selected.
Here is an example:

plot(1)
for(i in 1:3) {
tq()
# I want the window from tq to disappear after pressing ok
# then wait until after a point has been selected before
# reappearing.  But how?
locator(1)
}

where 

"tq" <-
function(){
  base <- tktoplevel()
  done <- tclVar(0)
  q.but <- tkbutton(base,text="Quit",
                    command=function()tclvalue(done) <- 1)
  tkpack(q.but)
  tkbind(base, "<Destroy>", function()tclvalue(done) <- 2)
  tkwait.variable(done)
  if(tclvalue(done)=="2") stop("aborted")
  tkdestroy(base)
}

I am working on Solaris using R 1.5.0.

Robert Denham




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