---
title: Sub-Windows
order: 7
layout: page
---

[[layout.sub-window]]
= Sub-Windows

ifdef::web[]
[.sampler]
image:{live-demo-image}[alt="Live Demo", link="http://demo.vaadin.com/sampler/#ui/structure/window"]
endif::web[]

__Sub-windows__ are floating panels within a native browser window. Unlike
native browser windows, sub-windows are managed by the client-side runtime of
Vaadin using HTML features. Vaadin allows opening, closing, resizing, maximizing
and restoring sub-windows, as well as scrolling the window content.

[[figure.layout.sub-window.basic]]
.A Sub-Window
image::img/subwindow-basic.png[width=50%, scaledwidth=70%]

Sub-windows are typically used for __Dialog Windows__ and __Multiple Document
Interface__ applications. Sub-windows are by default not modal; you can set them
modal as described in <<layout.sub-window.modal>>.

[[layout.sub-window.openclose]]
== Opening and Closing Sub-Windows

You can open a new sub-window by creating a new [classname]#Window# object and
adding it to the UI with [methodname]#addWindow()#, typically in some event
listener. A sub-window needs a content component, which is typically a layout.

In the following, we display a sub-window immediately when a UI opens:


[source, java]
----
public static class SubWindowUI extends UI {
    @Override
    protected void init(VaadinRequest request) {
        // Some other UI content
        setContent(new Label("Here's my UI"));

        // Create a sub-window and set the content
        Window subWindow = new Window("Sub-window");
        VerticalLayout subContent = new VerticalLayout();
        subWindow.setContent(subContent);

        // Put some components in it
        subContent.addComponent(new Label("Meatball sub"));
        subContent.addComponent(new Button("Awlright"));

        // Center it in the browser window
        subWindow.center();

        // Open it in the UI
        addWindow(subWindow);
    }
}
----

The result was shown in <<figure.layout.sub-window.basic>>. Sub-windows by
default have undefined size in both dimensions, so they will shrink to fit the
content.

The user can close a sub-window by clicking the close button in the upper-right
corner of the window. The button is controlled by the __closable__ property, so
you can disable it with [methodname]#setClosable(false)#. You can also use keyboard
shortcuts for closing a sub-window.  You can manage the shortcuts with the [methodname]#addCloseShortcut()#,
[methodname]#removeCloseShortcut()#, [methodname]#removeAllCloseShortcuts()#,
[methodname]#hasCloseShortcut()#, and [methodname]#getCloseShortcuts()# methods.

You close a sub-window also programmatically by calling the
[methodname]#close()# for the sub-window, typically in a click listener for an
[guibutton]#OK# or [guibutton]#Cancel# button. You can also call
[methodname]#removeWindow()# for the current [classname]#UI#.

[[layout.sub-window.openclose.example]]
=== Sub-Window Management

Usually, you would extend the [classname]#Window# class for your specific
sub-window as follows:


[source, java]
----
// Define a sub-window by inheritance
class MySub extends Window {
    public MySub() {
        super("Subs on Sale"); // Set window caption
        center();

        // Disable the close button
        setClosable(false);

        setContent(new Button("Close me", event -> close()));
    }
}
----

You could open the window as follows:


[source, java]
----
// Some UI logic to open the sub-window
final Button open = new Button("Open Sub-Window");
open.addClickListener(event -> {
    MySub sub = new MySub();

    // Add it to the root component
    UI.getCurrent().addWindow(sub);
});
----


[[layout.sub-window.position]]
== Window Positioning

When created, a sub-window will have an undefined default size and position. You
can specify the size of a window with [methodname]#setHeight()# and
[methodname]#setWidth()# methods. You can set the position of the window with
[methodname]#setPositionX()# and [methodname]#setPositionY()# methods.


[source, java]
----
// Create a new sub-window
mywindow = new Window("My Dialog");

// Set window size.
mywindow.setHeight("200px");
mywindow.setWidth("400px");

// Set window position.
mywindow.setPositionX(200);
mywindow.setPositionY(50);

UI.getCurrent().addWindow(mywindow);
----


[[layout.sub-window.scrolling]]
== Scrolling Sub-Window Content

((("scroll bars", id="term.layout.sub-window.scrolling.scrollbars", range="startofrange")))


If a sub-window has a fixed or percentual size and its content becomes too big
to fit in the content area, a scroll bar will appear for the particular
direction. On the other hand, if the sub-window has undefined size in the
direction, it will fit the size of the content and never get a scroll bar.
Scroll bars in sub-windows are handled with regular HTML features, namely
[literal]#++overflow: auto++# property in CSS.
((("overflow")))

((("[interfacename]#Scrollable#")))
As [classname]#Window# extends [classname]#Panel#, windows are also
[interfacename]#Scrollable#. Note that the interface defines __programmatic
scrolling__, not scrolling by the user. Please see
<<layout-panel#layout.panel,"Panel">>.

(((range="endofrange", startref="term.layout.sub-window.scrolling.scrollbars")))

[[layout.sub-window.modal]]
== Modal Sub-Windows

A modal window is a sub-window that prevents interaction with the other UI.
Dialog windows, as illustrated in <<figure.layout.sub-window.modal>>, are
typical cases of modal windows. The advantage of modal windows is limiting the
scope of user interaction to a sub-task, so changes in application state are
more limited. The disadvantage of modal windows is that they can restrict
workflow too much.

You can make a sub-window modal with [methodname]#setModal(true)#.

[[figure.layout.sub-window.modal]]
.Modal Sub-Window
image::img/subwindow-modal.png[width=70%, scaledwidth=100%]

Depending on the theme, the parent window may be grayed when the modal window is
open.


[WARNING]
.Security Warning
====
Modality of child windows is purely a client-side feature and can be
circumvented with client-side attack code. You should not trust in the modality
of child windows in security-critical situations such as login windows.

====