gcombobox: combobox implementation
In gWidgetsWWW2: Toolkit implementation of the gWidgets API for use with web pages

Description Usage Arguments Details Value Note Examples

The svalue<- method is used to specify value by name or by index.

The name gdroplist is an alternative (not encouraged) for gcombobox

gcombobox(items, selected = 1, editable = FALSE, coerce.with = NULL,
  handler = NULL, action = NULL, container = NULL, ..., width = NULL,
  height = NULL, ext.args = NULL, autocomplete = FALSE,
  initial.msg = "", tpl = NULL)

gdroplist(items, selected = 1, editable = FALSE, coerce.with = NULL,
  handler = NULL, action = NULL, container = NULL, ..., width = NULL,
  height = NULL, ext.args = NULL, autocomplete = FALSE,
  initial.msg = "", tpl = NULL)

`items`	a vector or data frame of items to choose from. Coerced to character class. Use `coerce.with` to get a numeric value, say. If a data frame then one can add an icon, tooltip, and possibly extra information: with 1 column (items), two columns (items, icons), or three columns (items, icons, tooltip)). If 4 or more, then extra columns can be incorporated by specifying a template. The icon is a url, not a stock name. For stock icons, convert with `getStockIconByName` with `css=FALSE` specified.
`selected`	initially selected item, by index. Use `0L` for none.
`editable`	logical. Does combobox allow editing. A bug (or package writer's limitations) in extjs do not allow one to set the value if it is a potential index (when `items` is integer). Go figure. Use 4.0, not 5 if you want numeric values ...
`coerce.with`	Function. If given, called on value before returning
`handler`	optional means (to `addHandlerChanged`) to specify a handler for the default signal. A handler is a function with signature `(h,...)` where `h` is a list with components `obj` referring to the object emitting the signal, `action` containing values passed to the `action` argument, and possible other values.
`action`	Passed to handler to parameterize a call
`container`	A parent container. In gWidgetsWWW2 a parent container is not optional (though it can be substituted with the `parent` argument in some circumstances). The parent specifies the widget heirarchy and the `...` argument is used to pass along arguments to layout the child component in the parent container. Typically, these are passed to the `add` method of the parent container.
`...`	Used to pass along argument to the parent container's `add` method and possible other arguments to the underlying ference class constructors.
`width`	width in pixels of component. Sizing in gWidgetsWWW2 is sometimes necessary as the arguments `expand` and `fill` are not well implemented.
`height`	height in pixels of the component.
`ext.args`	The contructors of gWidgetsWWW2 ultimately call an Ext constructor. The options passed to the Ext constructor may be added to or overridden by use of this argument. Values are passed in as named list components and with values converted into JavaScript objects by `asJSObject`.
`autocomplete`	If `TRUE`, will hide the trigger and make editable. When the user types the matching values are presented. (This is also the default behaviour, but if the object is not editable, only valid values are stored.)
`initial.msg`	If `selected=0`, then one can assign an initial message here
`tpl`	a template for the item. This is an HTML snippet, where the column names, when wrapped in braces, will be substituted for the values. The first three columns have their names normalized to `name`, `icon`, `tooltip`.

The default change handler differs depending whether the field is editable. If not, then the handler is called before the selection is finalized. Otherwise, the handler is called on the "change" event, which is to track "user-initiated change is detected in the value of the field." This does not always fire on selection by an item. To force that, use the add_handler_select method.

an ExtWidget instance

The [<- method is note working. The tpl argument is not working as we'd like.

w <- gwindow()
sb <- gstatusbar("Powered by gWidgetsWWW and Rook", cont=w)
g <- ggroup(cont=w, horizontal=FALSE)
cb <- gcombobox(state.name, cont=g)
addHandlerChanged(cb, handler=function(h,...) {
galert(paste("You selected ", svalue(h$obj), sep=""), parent=w)
})
## initial message
gcombobox(state.name, cont=g, selected=0, initial.msg="Choose a state...")
## autocomplete
 cb <- gcombobox(state.name, cont=g, autocomplete=TRUE)
## template
w <- gwindow()
g <- gvbox(container=w)
tmp <- "http://upload.wikimedia.org/wikipedia/commons/thumb/"
icons = paste(tmp, c("5/5c/Flag_of_Alabama.svg/22px-Flag_of_Alabama.svg.png",
                     "e/e6/Flag_of_Alaska.svg/22px-Flag_of_Alaska.svg.png",
                     "9/9d/Flag_of_Arizona.svg/22px-Flag_of_Arizona.svg.png"), sep="")
d <- data.frame(name=c("Alabama", "Alaska","Arizona"),
                icon=icons,
                tooltip=c("Audemus jura nostra defendere",
                  "North to the future",
                  "Ditat Deus"
                  ),
                extra=c(
                  "Montgomery",
                  "Juneau",
                  "Phoenix"),
                stringsAsFactors=FALSE)
cb <- gcombobox(d,
                tpl="<img src=\"{icon}\"></img><span data-qtip=\"{tooltip}\"> {name},
                      Capital is <em>{extra}</em></span>",
                cont=g)