[R] Tcl/Tk and mouse

[Peter Wolf]

 Within a loop I tried to draw some things in
 dependency on the position of the mouse.
 This works fine with R-1.5.1 but R-1.6.1
 requires to include some delay by
 Sys.sleep(delay)  with  delay>=0.015.
 For smaller values (e.g. 0.0001) the
 top level tcltk-window does not appear
 and so I am not able to control the elements
 to be plotted using the tcltk-widget.

 Question1: How can I force the tcltk-widget
            to appear / to get the position
            of the mouse within the loop?

 Question2: Why isn't it allowed to use the
            locator function with n=0, with
            the meaning to output the
            coordinates of the mouse?
            ( Then my problem can be
              solved without Tcl/Tk )

 Here is an example:

# Definition of function a:
#
####################################
a<-function(delay=0.015){
  library(tcltk)
  state <-tclVar("relax")
  number<-tclVar("100")
  top   <-tktoplevel()
  show  <-tklabel (top,textvariable=number)
  up    <-tkbutton(top,text="up")
  down  <-tkbutton(top,text="down")
  exit  <-tkbutton(top,text="exit",command=function()
tclvalue(state)<-"exit" )
  tkpack(show,up,down,exit)
  tkbind(up,  "<Enter>",function() tclvalue(state)<-"up" )
  tkbind(up,  "<Leave>",function() tclvalue(state)<-"relax" )
  tkbind(down,"<Enter>",function() tclvalue(state)<-"down" )
  tkbind(down,"<Leave>",function() tclvalue(state)<-"relax" )
  plot(1:400,type="n"); old<-1:2; x<-1; y<-200
  repeat{
    Sys.sleep(delay)
    choice <- tclvalue(state)
    if((x<-x+1)>400) break
    if(choice=="exit")break
    if(choice=="up"  ) y<-y+1
    if(choice=="down") y<-y-1
    if(choice=="relax")y<-y
    points(old[1],old[2],col="red")
    points(x,     y,     col="black")
    tclvalue(number) <- as.character(y)
    old<-c(x,y)
  }
  tkdestroy(top)
}
#
###############################
# a(0.01) is ok, a(0.0001) is not ok by:
#
# version:
# platform hppa2.0-hp-hpux10.20
# arch     hppa2.0
# os       hpux10.20
# system   hppa2.0, hpux10.20
# status
# major    1
# minor    6.1
# year     2002
# month    11
# day      01
# language R
##############################

Peter Wolf

-----------------------------

H.P. Wolf
University of Bielefeld, Germany
pwolf at wiwi.uni-bielefeld.de