gWidgets2 (version 1.0-9)

gbutton: Basic button widget

Description

The basic button widget is a standard means to provide the user a mechanism to invoke an action. This action may be specified by a handler or by a gaction object. The main property for GButton is the label text. If this text matches a stock icon name and the toolkit supports it, an icon will accompany the button.

The svalue method for a button object refers to its main property, the button label

Usage

gbutton(
  text = "",
  handler = NULL,
  action = NULL,
  container = NULL,
  ...,
  toolkit = guiToolkit()
)
.gbutton(toolkit, text, handler, action, container, ...)
# S3 method for GButton
addHandlerChanged(obj, handler, action = NULL, ...)
# S3 method for GButton
svalue(obj, index = NULL, drop = NULL, ...)

Arguments

text

label text. If text matches a stock icon name, that is used as well

handler

A handler assigned to the default change signal. Handlers are called when some event triggers a widget to emit a signal. For each widget some default signal is assumed, and handlers may be assigned to that through addHandlerChanged or at construction time. Handlers are functions whose first argument, h in the documentation, is a list with atleast two components obj, referring to the object emitting the signal and action, which passes in user-specified data to parameterize the function call.

Handlers may also be added via addHandlerXXX methods for the widgets, where XXX indicates the signal, with a default signal mapped to addHandlerChanged (cf. addHandler for a listing). These methods pass back a handler ID that can be used with blockHandler and unblockHandler to suppress temporarily the calling of the handler.

action

User supplied data passed to the handler when it is called

container

A parent container. When a widget is created it can be incorporated into the widget heirarchy by passing in a parent container at construction time. (For some toolkits this is not optional, e.g. gWidgets2tcltk or gWidgets2WWW2.)

...

These values are passed to the add method of the parent container. Examples of values are expand, fill, and anchor, although they're not always supported by a given widget. For more details see add. Occasionally the variable arguments feature has been used to sneak in hidden arguments to toolkit implementations. For example, when using a widget as a menubar object one can specify a parent argument to pass in parent information, similar to how the argument is used with gaction and the dialogs.

toolkit

Each widget constructor is passed in the toolkit it will use. This is typically done using the default, which will lookup the toolkit through guiToolkit.

obj

object receiving event and emitting a signal to the handler

index

NULL or logical. If TRUE and widget supports it an index, instead of a value will be returned.

drop

NULL or logical. If widget supports it, drop will work as it does in a data frame or perhaps someother means.

Value

a GButton instance. While this object has its own (reference) methods, one primarily interacts with it through S3 methods defined within the package.

Examples

# NOT RUN {
if(interactive()) {

  w <- gwindow("Buttons", visible=FALSE)
  g <- ggroup(cont=w, horizontal=FALSE)

  ## various buttons

  ## with icons
  b1 <- gbutton("open", cont=g)

  ## without icon
  b2 <- gbutton("ouvrir", cont=g)

  ## by an action
  act <- gaction("open", tooltip="open", icon="open", handler=function(...) {})
  b3 <- gbutton(action=act, cont=g)

  ## with a handler
  b4 <- gbutton("click me", cont=g, handler=function(h,...) {
    if(svalue(b2) == "open")
      svalue(b2) <- "ouvrir"
    else
      svalue(b2) <- "open"
  })


  ## handlers can be blocked/unblocked
  b5 <- gbutton("Click me for a message", cont=g)
  id <- addHandlerClicked(b5, function(h,...) print("Ouch"))
  b6 <- gcheckbox("toggle handler message", cont=g, use.togglebutton=TRUE, handler=function(h,...) {
      if (svalue(b6)) {
          blockHandler(b5, id)
      } else {
          unblockHandler(b5, id)
      }
  })
  
  visible(w) <- TRUE
}
# }