[R] tcltk: Difficulties creating menus

[Peter Dalgaard BSA]

Dirk Eddelbuettel <edd at debian.org> writes:

> I am struggling with adding menus to a tcltk application. The following
> example (from the O'Reilly book on Perl/Tk) works fine:
> 
> #!/usr/bin/perl -w
> use Tk;
> my $mw = MainWindow->new;
> $menub = $mw->Menubutton(-text => "Color")->pack();
> foreach (qw/red yellow green blue grey/) {
>   $menub->radiobutton(-label => $_, -command => \&set_bg,
>                       -variable => \$background_color, -value => $_);
> }
> MainLoop;
> sub set_bg {
>   print "Background value is now: $background_color\n";
>   $mw->configure(-background => $background_color);
> }
> 
> I cannot get anything similar to work under R. Adding a tkmenubutton is
> easy, but I fail to get it to "connect" to an actual menu composed of 
> check or radiobuttons:
> 
> library(tcltk)
> color<-"blue"
> tt <- tktoplevel()
> tkpack(mb <- tkmenubutton(tt, text="Color"))
> ## does nothing
> ## tkradiobutton(mb, variable=color, text="blue", value="blue",
> ##              command=set.bg)
> ##
> ## Error: Error in .Tcl(.Tcl.args(...)) :
> ##  		[tcl] bad option "add": must be cget or configure.
> ## tkadd(mb, tkcheckbutton, label="blue", variable=color)
> ##
> ## Dito
> ## tkcmd("add", tkcheckbutton, label="blue", variable=color)
> tkpack(tkbutton(tt, text="Quit", command=function()tkdestroy(tt)))
> 
> Any pointers or examples would be greatly appreciated.

Variables need special handling. You cannot just link to an R variable
(because they tend to move around in memory when you assign them) as
you can in Tcl or Perl/Tk. The convention is (for now anyway)

tkxxx(...., variable="color",....)
tclvar$color <- "blue"
-etc-

Also note that Perl/Tk does its own sneaky things with the control
language, in particular it bypasses the creation of a menu widget, to
make everything more object oriented.

The R interface would be closer to the Tcl:

library(tcltk)
tclvar$color<-"blue"
tt <- tktoplevel()
tkpack(mb <- tkmenubutton(tt, text="Color"))
m <- tkmenu(mb)
tkconfigure(mb,menu=m)
for ( i in c("red", "blue", "green"))
   tkadd(m, "radio", label=i, variable="color", value=i)

(And I was just getting to this bit for the Rnews paper that Kurt has
been nagging me for. Thanks...)
-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
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