Create a Dialog instance

Description

A dialog is like an item group, in that it combines items into a model. However, an item group is meant to be incorporated into other GUIS, whereas a dialog creates its own window and decorations. A dialog has default buttons, and options for adding in menubars, toolbars, and statusbars. The choice of buttons can be specified at construction.

Usage

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aDialog(items = list(), title = "", help_string = "", buttons = c("OK",
  "SPACE", "Cancel", "Help"), ...)

Arguments

items

List of item instances to create the model for the dialog object. May also be an item group (anItemGroup).

title

Title of dialog

help_string

String for default Help button

buttons

Character vector of button names. "OK","Cancel","Help","Undo","Redo" are some standard ones. "SPACE" and "SPRING" adjust the layout.

...

How to pass in other properties and methods of the dialog object. For example OK_handler.

Details

Methods:

The main method that a dialog has is its OK_handler which is a method called when the "OK" button is clicked (one of the default buttons).

The getters and setters for the main value for an item are get_NAME and set_NAME, where NAME is the item name. The name is specified when the item is constructed (through its name property) or more conveniently, taken from the name of the component in the items list that defines the items for dialog or item group.

The method to_R returns the items' values as a list (useful in combination with do.call).

The method get_item_by_name returns an item object by its name. (Names should be unique.) This is useful if more properties than the main one for an item are needed to be set. (The main value is set via the setter.) The example shows how the validate property of some items can be set.

The method is_valid is TRUE if all items validate and FALSE otherwise.

The method model_value_changed(.) is called whenever an item property is changed either through the GUI. A dialog observes itself.

For each item one can listen for changes with the method property_NAME_value_changed(., value, old_value).

Properties that are of interest:

  1. status_text If non-NULL, when GUI is drawn, a status bar will be made with this text. The method set_status_text can be used to update the status

  2. menu_list A menu list to specify a menubar. (See gmenu.)

  3. toolbar_list A menu list to specify a toolbar. (See gtoolbar.)

  4. buttons A list of buttons names. The default is c("OK", "SPACE", "Cancel", "Help"). The special names SPACE and SPRING adjust their positioning, otherwise the values are button names. When a button is clicked, the handler buttonname_handler is called, where the buttonname is stripped on non-alphanumeric characters. The basic buttons and Redo and Undo have default handlers. Likely, only OK_handler will need redefining. The property default_button can be specified to make a button the default one (so that it is activated when a user presses the enter key).

Value

Returns a proto object. See its show_help method for details.

Examples

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##
## a Basic example
dlg <- aDialog(items=list(
                 a = numericItem(0),
                 b = stringItem("a")
                 ),
               title="The title",
               help_string="Help on this dialog"
               )
## Not run: dlg$make_gui()
##
##
## example with model_value_changed
plotIt <- function(n, mean, sd, ...) hist(rnorm(n, mean, sd))
dlg <- aDialog(items=list(
  n = integerItem(10),
  mean = numericItem(0),
  sd = numericItem(1),
  out=graphicDeviceItem()
),
buttons="Cancel",
model_value_changed=function(.) if(.$is_valid()) do.call("plotIt", .$to_R())
)
##
## validation for n, sd
n <- dlg$get_item_by_name("n")
n$validate <- function(., rawvalue) {
  if(rawvalue <= 1) stop("n must be positive integer") else rawvalue
}
sd <- dlg$get_item_by_name("sd")
sd$validate <- function(., rawvalue) {
  if(rawvalue <- 0) stop("sd must be positive") else rawvalue
}
## Not run: dlg$make_gui()
##
##
## subtle point about scope. Proto methods can be defined via $<- or [[<- but there is a difference.
## $<- does not have lexical scope whereas [[<- does. The $<- might be more natural to type,
## but [[<- might be more natural to use. In this example,
## The "b" button does not work, as it can't find the
## function a -- the frame of evaluation is the environment dlg (not its enclosing frame).
## Thanks to Gabor for his help with this.
scope_example <- function() {
a <- function(...) print("hi")
dlg <- aDialog(items=list(),
                buttons=c("a","b","c"),
                a_handler=function(.) a(),   ## like [[<-, not $<-
                title="a, c work; b doesn't"
                )
 dlg$b_handler <- function(.) a()  ## $<- has unbound variables found in dlg
 dlg[['c_handler']] <- a           ## [[<- uses lexical scope for unbound variables
}
## Not run: scope_example()
## See ?anItemGroup for an example of a modal dialog

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