gtree: Constructor for widget to display heirarchical dta
In gWidgets: gWidgets API for Building Toolkit-Independent, Interactive GUIs

Description Usage Arguments Details Examples

This widget allows tree-like data to be presented. Each node on the tree should be a data frame with the same column structure. The first column is treated like a key, and should be unique. Offspring are specified through a function of the keys which are ancestors. This function returns the data frame to be displayed. Values in the tree can be selected with the mouse. This value can be retrieved through a method, or a handler can be assigned to double click events.

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gtree(offspring = NULL, hasOffspring = NULL, offspring.data = NULL,
col.types = NULL, icon.FUN = NULL, chosencol = 1, multiple = FALSE,
handler = NULL, action = NULL, container = NULL, ..., toolkit = guiToolkit())

`offspring`	A function to produce a data frame. The first column of the data frame is used as a key. It should be unique, otherwise the updating will not work properly. The `offspring` function has two arguments, the first being the path (the first column of the offspring data frame is the key, and the path is the vector of keys) and the value of `offspring.data`. The data frame can determine whether an entry has offspring, by having the second column be a logical vector, `TRUE` if there is offspring, `FALSE` if not.
`hasOffspring`	Whether an entry has an offspring is determined by a. if this function is non-`NULL` and it returns a `TRUE` value when called on the offspring data frame for this row, b. if this is NULL and the second column of the offspring data frame is a logical vector and for this row is `TRUE`. If this function is `NULL` and the second column is not a logical vector then it is assumed that there are no offspring.
`offspring.data`	Passed to `offspring` function to parameterize that function.
`col.types`	Used to determine the type of column, given as a data frame with 1 or more rows. Otherwise it is determined by first row of offspring data frame. If the offspring function can return an empty data frame, then this argument should be given.
`icon.FUN`	An optional function to determine an icon place into the first column. This function gets called with the data in `offspring`, and should return a row vector of length `nrow(offspring)`. The icons are stock icons, and should be referenced by name. The helper function `getStockIcons` list all the available stock icons.
`chosencol`	The column used when requesting the selected row's value. Defaults to first
`multiple`	A logical to determine if multiple selection is allowed. Defaults to `FALSE`
`handler`	Handler for double click events
`action`	Passed to handler
`container`	Optional container to attach widget to.
`...`	Passed to `add` method of container
`toolkit`	Which GUI toolkit to use

In an abstract sense, these trees are specified by a function which produces the value at a given node from the ancestry of the given node, and a function specifying if a node has offspring.

The offspring function determines the displayed data for a certain node. It has signature (path, offspring.data), where the path consists of the ancestors and offspring.data is an optional value passed in when the tree object is constructed. This function returns a data frame. Its first column should consist of unique values, as it is treated like a key.

The hasOffspring function is called on the return value of offspring. It should return a logical indicating which rows have offspring. If this argument is not present, then the second column of the return values of offspring are consulted. If these are logical, then they are used to determine if offspring are present. Otherwise, no offspring are assumed.

The icon.FUN function is called on the return value of offspring. If present, it should return a vector of stock icon names.

The svalue method returns the current key. The index argument has changed. If index is TRUE, the path of each selection is returned as a numeric vector, where the numbers represent the sibling count at each level, 1-based. That is c(1,2,3) is the 3rd offspring of the second offspring of the first offspring of the root. If more than one selection is made, then a list of such values is returned. This way – in theory – we can set values by index too. In particular, we should have svalue(obj, index=TRUE) <- svalue(obj, index=TRUE). (Before, using a numeric value for index would give the ith column, as opposed to the chosen column. This behaviour can be found using the "[" method.)

The "[" method refers to the vector of keys for the selected object. That is, svalue gives the current key, and [ returns the path of keys.

The addHandlerDoubleclick handler (also addHandlerChanged) can be set to respond to a double click event.

The addHandlerClicked handler should be called when the selection is changed.

## Not run: 
 ## function to find offspring
 offspring <- function(path, offspring.data=NULL) {
         if(length(path) > 0) 
           directory <- paste(getwd(), .Platform$file.sep,
                              paste(path,collapse=.Platform$file.sep),
                              sep="")
         else
           directory <- getwd()

         files <- file.info(dir(path=directory, full.names=TRUE))[,c(1,2,3)]
         files <- data.frame(filename=dir(path=directory),
                             isdir=files[,2],
                             size=as.integer(files[,1]),
                             mode=as.character(files[,3]),
                             stringsAsFactors=FALSE)
         return(files)
 }
 hasOffspring <- function(children,offspring.data=NULL, ...) {
   return(children$isdir)
 }
 icon.FUN <- function(children,offspring.data=NULL, ...) {
   x <- rep("file", length=nrow(children))
   x[children$isdir] <- "directory"
   return(x)
  }
  ## shows isdir directory, as hasOffspring is specified
  w <- gwindow("test with isdir showing")
  gtree(offspring, hasOffspring, icon.FUN = icon.FUN, container=w)

  ## does not show isdir directory, as hasOffspring=NULL and
  ## second column is a logical
  w <- gwindow("tree test no dir column")
  tr <- gtree(offspring, hasOffspring=NULL, icon.FUN = icon.FUN, container=w)

  ## Show a fixed list using a dynamic tree
l <- list(a=list(
            aa=1,
            ab=2,
            ac=list(ac1=1)
            ),
          b=list(
            ba=list(
              baa=1,
              bab=list(
                baba=1
                )
              )
            ))

offspring <- function(path, ...) {
  print(path)
  ll <- l
  if(length(path) > 0) {
    for(i in path)
      ll <- ll[[i]]
  }
  out <- data.frame(name=names(ll),
                    hasOffspring=!sapply(ll, is.atomic),
                    value=as.character(sapply(ll, function(i) ifelse(is.atomic(i), i, ""))),
                    stringsAsFactors=FALSE)
  out
}

w <- gwindow("Tree from list")
tr <- gtree(offspring=offspring, container=w)

addHandlerDoubleclick(tr, handler=function(h,...) {
  print(svalue(h$obj))		# the key
  print(h$obj[])		# vector of keys
})



## End(Not run)