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Modals, windows and toasts

A KVision application can use three types of windows - modal dialogs, floating, re-sizable windows and toasts. Modals can be used to create popups with information messages, alerts, warnings or custom forms and buttons. Floating windows can be used to split your GUI into any number of separate parts, to work with them simultaneously (multiple documents, floating toolbars etc.). With Bootstrap toasts you can display lightweight notifications, designed to mimic the push notifications that have been popularized by mobile and desktop operating systems.
These components are only available with the kvision-bootstrap module.


Modal components are grouped in the io.kvision.modal package. The base class for all modals is io.kvision.modal.Modal. You can use this class to create a modal with any content you need - just add your components to the container. You can use the standard add method to add typical components or containers to your modal. You can also use the addButton method to add some buttons to the footer of the modal (these buttons will be right-aligned by default).
Modal dialogs are automatically added to the components tree, so there is no need to add them to any container. Modals are invisible by default. Use show method of the Modal class to make it visible.
val modal = Modal("Custom modal dialog")
modal.add(H4("Lorem ipsum dolor sit amet, consectetur adipiscing elit."))
modal.addButton(Button("Close").onClick {
The Modal class constructor has additional parameters for a caption, the size of the modals text, visibility of the close button, disabling animation effects and the function of the Escape key.
val modal = Modal("A caption", size = ModalSize.LARGE, closeButton = false,
animation = false, escape = false)
There are some ready to use, convenience subclasses of the Modal class.

Alert popups

Alert popup is a simple modal window that shows information text and an OK button. You can use the companion function Alert.show(...) to easily create and display an Alert window. You can define a callback function for the OK button. You can also change some other parameters of the popup (e.g. size, align, rich content or disabling animation effect).
Alert.show("Alert dialog", "Lorem ipsum dolor sit amet, consectetur adipiscing.") {
// A callback function body for the OK button.

Confirm popups

Confirm popup is a simple modal window which displays a question and two (YES / NO) or three (YES / NO / CANCEL) buttons. You can also use the companion function Confirm.show(...) to easily create and display a Confirm popup. You can define two distinct callback functions for the YES and NO buttons. You can also change button titles (e.g. to support I18N) and some other parameters of the popup (e.g. size, align, rich content or disabling animation effect).
"Confirm dialog",
"Lorem ipsum dolor sit amet?",
animation = false,
align = Align.LEFT,
yesTitle = tr("YES"),
noTitle = tr("NO"),
cancelVisible = false,
noCallback = {
Alert.show("Result", "You pressed NO button.")
}) {
Alert.show("Result", "You pressed YES button.")

Dialog with a result

A io.kvision.modal.Dialog component allows you to create a dialog, which can return any data as a result. This class has a suspending method getResult(), which must be called inside a Kotlin coroutine. You can create a subclass of the Dialog class or use a Dialog instance directly. You should call setResult() method from your own code to pass your data back to the caller.
GlobalScope.launch {
val dialog = Dialog<String>("Dialog with result") {
add(Span("Press a button"))
addButton(Button("Button").onClick {
setResult("STRING RESULT")
val result = dialog.getResult()


The io.kvision.window.Window component allows you to create a number of floating, re-sizable windows inside your application. Every window has a frame, which can be used to change its size and position. The Window class constructor takes a number of parameters, two of which allow you to create windows that are not draggable and not re-sizable as well. When the window is not draggable, the close, minimize and maximize buttons are hidden and the caption is null - the caption bar won't be rendered at all.
Windows overlap each other - one is shown on top of the others. The window clicked (inside the window caption bar) is brought to the front. You can also use toFront() method to bring a given window to the front programmatically.
Unlike modals, window components have to be added to a container, and they are displayed in the context of their parent (e.g. you can hide all windows by hiding their parent container). But windows are not confined to the parent container area - they can be positioned anywhere inside the browser window.
window("Window", 600.px, 300.px, closeButton = true,
maximizeButton = true, minimizeButton = true, icon = "fas fa-edit") {
left = ((Random.nextDouble() * 800).toInt()).px
top = ((Random.nextDouble() * 300).toInt()).px
span("A window content")
Window caption can contain both minimize and maximize buttons, but the actual implementation of minimize and maximize functions must be done within the application. The Window component sends "maximizeWindow" and "minimizeWindow" events and both operations can be implemented by overriding toggleMaximize() and toggleMinimize() methods.


Bootstrap toasts are created using io.kvision.toast.ToastContainer class. First you need to create an instance of the container class with the appropriate position parameter. You should create only one container for a given position. Toast containers are automatically added to the components tree, so there is no need to add them to any other container.
You can display toasts with the showToast() method of the ToastContainer class.
val toastContainer = ToastContainer(ToastContainerPosition.TOPRIGHT)
"Some information message",
"Toast title"
With additional parameters of the showToast() method you can set text color, background color, turn off the animation effect, set auto-hide delay or disable auto-hide at all.