[R-gui] Automatic Widget Creation and Callbacks in RGtk

[Neil E. Klepeis]

Hi,

I apologize if this is not the proper forum.

I am writing a package to automatically create RGtk GUI's with an 
arbitrary number of widgets to act as a "control panel" front end for a 
user-specified plotting or simulation function.      The widgets are 
specified in a list argument to a function and associated with specific 
parameter values for the user function (FUN), which is called whenever a 
widget value is modified.   For example, a call to:

makegui <- function (w=list(x=100, y=200, FUN)) {...}

would result in a GUI with slider widgets for parameters "x" and "y". 
Whenever the sliders are changed, the function FUN is called with the 
new value of "x" or "y" -- possibly drawing a plot or something else.

MY PROBLEM IS THIS:    I want to make callbacks for each widget that 
automatically send new parameter values to the function FUN, but I can't 
find a way to do this with arbitrary numbers of widgets/parameters and 
arbitrary names for the widgets.    For convenience, I set the parameter 
names to be the same as the widget names.

First I store all initial parameter values in an array, e.g., params <- 
list(x=100, y=200).   widget.names <- c("x", "y")

I create each widget with something like:

assign(widget.name, gtkWidget(...))

Then I add a callback:

get(widget.name)$AddCallback("value-changed", function(w) 
{callbackFUN(...)})

I want the callbackFUN() function to be able to get the widget's value 
with something like w$GetValue() and put it into the "params" list, and 
then finally to send the parameter list to the FUN function.

I can't seem to find any way to send a character string of the 
appropriate arbitrary widget name to the callback function so that I can 
put the widget value into the parameter list.   I've tried setting an 
attribute of the widget with its associated parameter name when I create 
the callback, but the attribute seems to disappear when the callback is 
called.

I can get around all this whole problem by simply looping through all of 
the widgets at once by name:

for (i in widget.names) params[[i]] <- get(i)$GetValue()

but this approach is inefficient when only one parameter is changed at a 
time.

Am I missing something easy?

TIA for any ideas.

--Neil Klepeis