[R] Passing a pointer to .C() in Win32

[James Wettenhall]

Hi,

Is there any way to pass an integer from R to C and have 
it cast as a pointer?  

# Win32 Example:

library(tcltk)
tt <- tktoplevel()
hWndString <- tclvalue(tkwm.frame(tt))
# I'll avoid posting code to this function:
source("http://bioinf.wehi.edu.au/folders/james/R/hexStringToDecimalInteger.R")
hWnd <- hexStringToDecimalInteger(hWndString)
system32 <- file.path(Sys.getenv("windir"),"system32")
user32 <- file.path(system32,"user32.dll")
dyn.load(user32)

# WARNING: THIS NEXT LINE WILL PASS AN INVALID WINDOW HANDLE TO 
# USER32.DLL AND PROBABLY CRASH YOUR R SESSION!!!!
.C("SetForegroundWindow",hWnd)

# This above won't work, because .C() will pass a pointer to the 
# integer hWnd to SetForegroundWindow (in user32.dll) whereas 
# I want the integer hWnd to be cast as a pointer.

So for each DLL function I want to call with a pointer argument, 
do I have to define my own C function e.g. my_SetForegroundWindow 
(using the Windows API) which takes an integer argument instead 
and then casts it as a pointer in order to call the real 
SetForegroundWindow function?

Of course environments behave like pointers but they are 
read-only.  You can't do this (below), right?
mode(hWnd) <- "environment"

WHY WOULD I WANT TO DO ANYTHING LIKE THIS ABOVE?

I know that I can use tkfocus for Tk windows, but I have other 
applications in mind.  In Win32, when I run RGui with MDI, the 
bringToTop in tcltk's .onLoad brings the console to the top, but 
doesn't focus it, i.e. after library(tcltk), I can't type into 
the console until I click on it.  Now if I had RConsole->handle 
from the GraphApp code for RGui, maybe I could try something 
like SetForegroundWindow... For more info, go to 
http://msdn.microsoft.com and search for "BringWindowToTop", 
search for "SetForegroundWindow", and compare...

Maybe for this particular application, something like 
show(RConsole) might be better, (see R-devel thread below)
http://www.mail-archive.com/r-devel@stat.math.ethz.ch/msg01829.html

but I'm still wondering if casting to pointers can be done...

Another application is specifying a Tk window to be "Always On 
Top" using user32.dll's SetWindowPos function (again, search 
for it on http://msdn.microsoft.com).

Regards,
James