path: root/documentation/components/components-features.asciidoc

---
title: Common Component Features
order: 3
layout: page
---

[[components.features]]
= Common Component Features

The component base classes and interfaces provide a large number of features.
Let us look at some of the most commonly needed features. Features not
documented here can be found from the Java API Reference.

The interface defines a number of properties, which you can retrieve or
manipulate with the corresponding setters and getters.

[[components.features.caption]]
== Caption

((("caption property")))
((("Component interface", "caption")))
A caption is an explanatory textual label accompanying a user interface
component, usually shown above, left of, or inside the component. The contents
of a caption are automatically quoted, so no raw HTML can be rendered in a
caption.

The caption text can usually be given as the first parameter of a constructor of
a component or with [methodname]#setCaption()#.

[source, java]
----
// New text field with caption "Name"
TextField name = new TextField("Name");
layout.addComponent(name);
----

The caption of a component is, by default, managed and displayed by the layout
component or component container inside which the component is placed. For
example, the [classname]#VerticalLayout# component shows the captions
left-aligned above the contained components, while the [classname]#FormLayout#
component shows the captions on the left side of the vertically laid components,
with the captions and their associated components left-aligned in their own
columns. The [classname]#CustomComponent# does not manage the caption of its
composition root, so if the root component has a caption, it will not be
rendered.

[[figure.components.features.caption.layoutmanaged]]
.Caption Management by [classname]#VerticalLayout# and [classname]#FormLayout#.
image::img/features-caption-layoutmanaged.png[width=50%,scaledwidth=65%]

Some components, such as [classname]#Button# and [classname]#Panel#, manage the
caption themselves and display it inside the component.

Icon (see <<components.features.icon>>) is closely related to caption and is
usually displayed horizontally before or after it, depending on the component
and the containing layout. Also the required indicator in field components is
usually shown before or after the caption.

An alternative way to implement a caption is to use another component as the
caption, typically a [classname]#Label#, a [classname]#TextField#, or a
[classname]#Panel#. A [classname]#Label#, for example, allows highlighting a
shortcut key with HTML markup or to bind the caption to a data source. The
[classname]#Panel# provides an easy way to add both a caption and a border
around a component.

=== CSS Style Rules


[source, css]
----
.v-caption {}
  .v-captiontext {}
  .v-caption-clearelem {}
  .v-required-field-indicator {}
----

A caption is be rendered inside an HTML element that has the
[literal]#++v-caption++# CSS style class. The containing layout may enclose a
caption inside other caption-related elements.

Some layouts put the caption text in a [literal]#++v-captiontext++# element. A
[literal]#++v-caption-clearelem++# is used in some layouts to clear a CSS
[literal]#++float++# property in captions. An optional required indicator in
field components is contained in a separate element with
[literal]#++v-required-field-indicator++# style.



[[components.features.description]]
== Description and Tooltips

((("description property")))
((("Component interface", "description")))
((("tooltips")))
All components (that inherit [classname]#AbstractComponent#) have a description
separate from their caption. The description is usually shown as a tooltip that
appears when the mouse pointer hovers over the component for a short time.

You can set the description with [methodname]#setDescription()# and retrieve
with [methodname]#getDescription()#.


[source, java]
----
Button button = new Button("A Button");
button.setDescription("This is the tooltip");
----

The tooltip is shown in <<figure.components.tooltip.plain>>.

[[figure.components.tooltip.plain]]
.Component Description as a Tooltip
image::img/tooltip-plain-withpointer-hi.png[width=30%, scaledwidth=100%]

A description is rendered as a tooltip in most components.

When a component error has been set with [methodname]#setComponentError()#, the
error is usually also displayed in the tooltip, below the description.
Components that are in error state will also display the error indicator. See
<<dummy/../../../framework/application/application-errors#application.errors.error-indicator, "Error Indicator and Message">>.

The description is actually not plain text, but you can use HTML tags to format
it. Such a rich text description can contain any HTML elements, including
images.


[source, java]
----
button.setDescription(
    "<h2><img src=\"../VAADIN/themes/sampler/"+
    "icons/comment_yellow.gif\"/>"+
    "A richtext tooltip</h2>"+
    "<ul>"+
    "  <li>Use rich formatting with HTML</li>"+
    "  <li>Include images from themes</li>"+
    "  <li>etc.</li>"+
    "</ul>");
----
See the http://demo.vaadin.com/book-examples-vaadin7/book#component.features.description.richtext[on-line example, window="_blank"].

The result is shown in <<figure.components.tooltip.richtext>>.

[[figure.components.tooltip.richtext]]
.A Rich Text Tooltip
image::img/tooltip-richtext-withpointer-hi.png[width=40%, scaledwidth=75%]

Notice that the setter and getter are defined for all fields in the
[classname]#Field# interface, not for all components in the
[classname]#Component# interface.


[[components.features.enabled]]
== Enabled

((("enabled property")))
((("Component interface", "enabled")))
The __enabled__ property controls whether the user can actually use the
component. A disabled component is visible, but grayed to indicate the disabled
state.

Components are always enabled by default. You can disable a component with
[methodname]#setEnabled(false)#.


[source, java]
----
Button enabled = new Button("Enabled");
enabled.setEnabled(true); // The default
layout.addComponent(enabled);

Button disabled = new Button("Disabled");
disabled.setEnabled(false);
layout.addComponent(disabled);
----

<<figure.components.features.enabled.simple>> shows the enabled and disabled
buttons.

[[figure.components.features.enabled.simple]]
.An Enabled and Disabled [classname]#Button#
image::img/features-enabled-simple.png[width=30%, scaledwidth=50%]

A disabled component is automatically put in read-only state. No client
interaction with such a component is sent to the server and, as an important
security feature, the server-side components do not receive state updates from
the client in the read-only state. This feature exists in all built-in
components in Vaadin and is automatically handled for all [classname]#Field#
components for the field property value. For custom widgets, you need to make
sure that the read-only state is checked on the server-side for all
safety-critical variables.

=== CSS Style Rules

Disabled components have the [literal]#++v-disabled++# CSS style in addition to
the component-specific style. To match a component with both the styles, you
have to join the style class names with a dot as done in the example below.


[source, css]
----
.v-textfield.v-disabled {
    border: dotted;
}
----

This would make the border of all disabled text fields dotted.

// TODO This may change to $v-button-disabled-opacity
In the Valo theme, the opacity of disabled components is specified with the
`$v-disabled-opacity`
ifndef::web[parameter.]
ifdef::web[parameter, as described in <<dummy/../../../framework/themes/themes-valo#themes.valo.variables,"Common Settings">>]

[[components.features.icon]]
== Icon

((("icon property")))
((("Component interface", "icon")))
An icon is an explanatory graphical label accompanying a user interface
component, usually shown above, left of, or inside the component. Icon is
closely related to caption (see <<components.features.caption>>) and is usually
displayed horizontally before or after it, depending on the component and the
containing layout.

The icon of a component can be set with the [methodname]#setIcon()# method. The
image is provided as a resource, perhaps most typically a
[classname]#ThemeResource#.


[source, java]
----
// Component with an icon from a custom theme
TextField name = new TextField("Name");
name.setIcon(new ThemeResource("icons/user.png"));
layout.addComponent(name);

// Component with an icon from another theme ('runo')
Button ok = new Button("OK");
ok.setIcon(new ThemeResource("../runo/icons/16/ok.png"));
layout.addComponent(ok);
----

The icon of a component is, by default, managed and displayed by the layout
component or component container in which the component is placed. For example,
the [classname]#VerticalLayout# component shows the icons left-aligned above the
contained components, while the [classname]#FormLayout# component shows the
icons on the left side of the vertically laid components, with the icons and
their associated components left-aligned in their own columns. The
[classname]#CustomComponent# does not manage the icon of its composition root,
so if the root component has an icon, it will not be rendered.

[[figure.components.features.icon]]
.Displaying an Icon from a Theme Resource.
image::img/features-icon.png[width=40%, scaledwidth=60%]

Some components, such as [classname]#Button# and [classname]#Panel#, manage the
icon themselves and display it inside the component.

In addition to image resources, you can use __font icons__, which are icons
included in special fonts, but which are handled as special resources. See
<<dummy/../../../framework/themes/themes-fonticon#themes.fonticon,"Font Icons">>
for more details.

=== CSS Style Rules

An icon will be rendered inside an HTML element that has the
[literal]#++v-icon++# CSS style class. The containing layout may enclose an icon
and a caption inside elements related to the caption, such as
[literal]#++v-caption++#.



[[components.features.locale]]
== Locale

((("locale property", "in [classname]#Component#")))
((("Component interface", "locale")))
The locale property defines the country and language used in a component. You
can use the locale information in conjunction with an internationalization
scheme to acquire localized resources. Some components, such as
[classname]#DateField#, use the locale for component localization.

You can set the locale of a component (or the application) with
[methodname]#setLocale()# as follows:


[source, java]
----
// Component for which the locale is meaningful
InlineDateField date = new InlineDateField("Datum");

// German language specified with ISO 639-1 language
// code and ISO 3166-1 alpha-2 country code.
date.setLocale(new Locale("de", "DE"));

date.setResolution(Resolution.DAY);
layout.addComponent(date);
----
See the http://demo.vaadin.com/book-examples-vaadin7/book#component.features.locale.simple[on-line example, window="_blank"].

The resulting date field is shown in <<figure.components.features.locale.simple>>.

[[figure.components.features.locale.simple]]
.Set locale for [classname]#InlineDateField#
image::img/features-locale-simple.png[width=40%, scaledwidth=60%]

ifdef::web[]
[[components.features.locale.get]]
=== Getting the Locale

((("[methodname]#getLocale()#")))
You can get the locale of a component with [methodname]#getLocale()#. If the
locale is undefined for a component, that is, not explicitly set, the locale of
the parent component is used. If none of the parent components have a locale
set, the locale of the UI is used, and if that is not set, the default system
locale is set, as given by [methodname]#Locale.getDefault()#.

The [methodname]#getLocale()# returns null if the component is not yet attached
to the UI, which is usually the case in most constructors, so it is a bit
awkward to use it for internationalization. You can get the locale in
[methodname]#attach()#, as shown in the following example:

[source, java]
----
Button cancel = new Button() {
    @Override
    public void attach() {
        super.attach();
        ResourceBundle bundle = ResourceBundle.getBundle(
            MyAppCaptions.class.getName(), getLocale());
        setCaption(bundle.getString(MyAppCaptions.CancelKey));
    }
};
layout.addComponent(cancel);
----
See the http://demo.vaadin.com/book-examples-vaadin7/book#component.features.locale.get-attach[on-line example, window="_blank"].

However, it is normally a better practice to use the locale of the current UI to
get the localized resource right when the component is created.

[source, java]
----
// Captions are stored in MyAppCaptions resource bundle
// and the UI object is known in this context.
ResourceBundle bundle =
    ResourceBundle.getBundle(MyAppCaptions.class.getName(),
        UI.getCurrent().getLocale());

// Get a localized resource from the bundle
Button cancel =
    new Button(bundle.getString(MyAppCaptions.CancelKey));
layout.addComponent(cancel);
----
See the http://demo.vaadin.com/book-examples-vaadin7/book#component.features.locale.get-ui[on-line example, window="_blank"].
endif::web[]

ifdef::web[]
[[component.features.locale.selecting]]
=== Selecting a Locale

A common task in many applications is selecting a locale. This is done in the
following example with a [classname]#ComboBox#, which gets the available locales
in Java.


[source, java]
----
// The locale in which we want to have the language
// selection list
Locale displayLocale = Locale.ENGLISH;

// All known locales
final Locale[] locales = Locale.getAvailableLocales();

// Allow selecting a language. We are in a constructor of a
// CustomComponent, so preselecting the current
// language of the application can not be done before
// this (and the selection) component are attached to
// the application.
ComboBox<Locale> select = new ComboBox<>("Select a language") {
    @Override
    public void attach() {
        super.attach();
        setValue(getLocale());
    }
};

select.setItems(Arrays.asList(locales));
select.setCaptionGenerator(locale -> locale.getDisplayName(displayLocale));
select.setValue(getLocale());

layout.addComponent(select);

// Locale code of the selected locale
Label localeCode = new Label("");
layout.addComponent(localeCode);

// A date field which language the selection will change
InlineDateField date =
    new InlineDateField("Calendar in the selected language");
date.setResolution(Resolution.DAY);
layout.addComponent(date);

// Handle language selection
select.onValueChange(locale -> {
    date.setLocale(locale);
    localeCode.setValue("Locale code: " +
                        locale.getLanguage() + "_" +
                        locale.getCountry());  
});
----
See the http://demo.vaadin.com/book-examples-vaadin7/book#component.features.locale.selection[on-line example, window="_blank"].

The user interface is shown in <<figure.components.features.locale.selection>>.

[[figure.components.features.locale.selection]]
.Selecting a locale
image::img/features-locale-selection.png[]

endif::web[]


[[components.features.readonly]]
== Read-Only

((("read-only property")))
((("Component interface", "read-only")))
The property defines whether the value of a component can be changed. The
property is mainly applicable to [classname]#Field# components, as they have a
value that can be edited by the user.

[source, java]
----
TextField readwrite = new TextField("Read-Write");
readwrite.setValue("You can change this");
readwrite.setReadOnly(false); // The default
layout.addComponent(readwrite);

TextField readonly = new TextField("Read-Only");
readonly.setValue("You can't touch this!");
readonly.setReadOnly(true);
layout.addComponent(readonly);
----

The resulting read-only text field is shown in
<<figure.components.features.readonly.simple>>.

[[figure.components.features.readonly.simple]]
.A read-only component
image::img/features-readonly-simple.png[width=50%, scaledwidth=80%]

Setting a layout or some other component container as read-only does not usually
make the contained components read-only recursively. This is different from, for
example, the disabled state, which is usually applied recursively.

Notice that the value of a selection component is the selection, not its items.
A read-only selection component doesn't therefore allow its selection to be
changed, but other changes are possible. For example, if you have a read-only
[classname]#Table# in editable mode, its contained fields and the underlying
data model can still be edited, and the user could sort it or reorder the
columns.

Client-side state modifications will not be communicated to the server-side and,
more importantly, server-side field components will not accept changes to the
value of a read-only [classname]#Field# component. The latter is an important
security feature, because a malicious user can not fabricate state changes in a
read-only field.

Also notice that while the read-only status applies automatically to the value
of a field, it does not apply to other component variables. A
read-only component can accept some other state changes from the client-side
and some of such changes could be acceptable, such as change in the scroll bar
position of a [classname]#Table#. Custom components should check the read-only
state for variables bound to business data.

////
TODO: Note this also in the Advanced: Security section.
Possibly also in the GWT chapter.
////

=== CSS Style Rules

Setting a normally editable component to read-only state can change its
appearance to disallow editing the value. In addition to CSS styling, also the
HTML structure can change. For example, [classname]#TextField# loses the edit
box and appears much like a [classname]#Label#.

A read-only component will have the [literal]#++v-readonly++# style. The
following CSS rule would make the text in all read-only [classname]#TextField#
components appear in italic.


[source, css]
----
.v-textfield.v-readonly {
    font-style: italic;
}
----



[[components.features.stylename]]
== Style Name

((("style name property")))
((("Component interface", "style name")))
The __style name__ property defines one or more custom CSS style class names for
the component. The [methodname]#getStyleName()# returns the current style names
as a space-separated list. The [methodname]#setStyleName()# replaces all the
styles with the given style name or a space-separated list of style names. You
can also add and remove individual style names with [methodname]#addStylename()#
and [methodname]#removeStyleName()#. A style name must be a valid CSS style
name.


[source, java]
----
Label label = new Label("This text has a lot of style");
label.addStyleName("mystyle");
layout.addComponent(label);
----

The style name will appear in the component's HTML element in two forms:
literally as given and prefixed with the component-specific style name. For
example, if you add a style name [literal]#++mystyle++# to a
[classname]#Button#, the component would get both [literal]#++mystyle++# and
[literal]#++v-button-mystyle++# styles. Neither form may conflict with built-in
style names of Vaadin. For example, [literal]#++focus++# style would conflict
with a built-in style of the same name, and an [literal]#++content++# style for
a [classname]#Panel# component would conflict with the built-in
[literal]#++v-panel-content++# style.

The following CSS rule would apply the style to any component that has the
[literal]#++mystyle++# style.

[source, css]
----
.mystyle {
    font-family: fantasy;
    font-style:  italic;
    font-size:   25px;
    font-weight: bolder;
    line-height: 30px;
}
----

The resulting styled component is shown in <<figure.components.features.stylename>>

[[figure.components.features.stylename]]
.Component with a custom style
image::img/features-stylename-simple.png[width=50%, scaledwidth=75%]

[[components.features.visible]]
== Visible

((("visible property")))
((("Component interface", "visible")))
Components can be hidden by setting the __visible__ property to __false__. Also
the caption, icon and any other component features are made hidden. Hidden
components are not just invisible, but their content is not communicated to the
browser at all. That is, they are not made invisible cosmetically with only CSS
rules. This feature is important for security if you have components that
contain security-critical information that must only be shown in specific
application states.

[source, java]
----
TextField invisible = new TextField("No-see-um");
invisible.setValue("You can't see this!");
invisible.setVisible(false);
layout.addComponent(invisible);
----

The resulting invisible component is shown in
<<figure.components.features.visible.simple>>.

[[figure.components.features.visible.simple]]
.An invisible component
image::img/features-visible-simple.png[]

Beware that invisible beings can leave footprints. The containing layout cell
that holds the invisible component will not go away, but will show in the layout
as extra empty space. Also expand ratios work just like if the component was
visible - it is the layout cell that expands, not the component.

If you need to make a component only cosmetically invisible, you should use a
custom theme to set it [literal]#++display: none++# style. This is mainly useful
for some special components that have effects even when made invisible in CSS.
If the hidden component has undefined size and is enclosed in a layout that also
has undefined size, the containing layout will collapse when the component
disappears. If you want to have the component keep its size, you have to make it
invisible by setting all its font and other attributes to be transparent. In
such cases, the invisible content of the component can be made visible easily in
the browser.

A component made invisible with the __visible__ property has no particular CSS
style class to indicate that it is hidden. The element does exist though, but
has [literal]#++display: none++# style, which overrides any CSS styling.


[[components.features.sizeable]]
== Sizing Components

((("[classname]#Sizeable# interface")))
Vaadin components are sizeable; not in the sense that they were fairly large or
that the number of the components and their features are sizeable, but in the
sense that you can make them fairly large on the screen if you like, or small or
whatever size.

The [classname]#Sizeable# interface, shared by all components, provides a number
of manipulation methods and constants for setting the height and width of a
component in absolute or relative units, or for leaving the size undefined.

The size of a component can be set with [methodname]#setWidth()# and
[methodname]#setHeight()# methods. The methods take the size as a floating-point
value. You need to give the unit of the measure as the second parameter for the
above methods. The available units are listed in
<<components.features.sizeable.units.table>> below.


[source, java]
----
mycomponent.setWidth(100, Unit.PERCENTAGE);
mycomponent.setWidth(400, Unit.PIXELS);
----

Alternatively, you can speficy the size as a string. The format of such a string
must follow the HTML/CSS standards for specifying measures.


[source, java]
----
mycomponent.setWidth("100%");
mycomponent.setHeight("400px");
----

The "[literal]#++100%++#" percentage value makes the component take all
available size in the particular direction (see the description of
[parameter]#Unit.PERCENTAGE# in the table below). You can also use the
shorthand method [methodname]#setSizeFull()# to set the size to 100% in both
directions.

The size can be __undefined__ in either or both dimensions, which means that the
component will take the minimum necessary space. Most components have undefined
size by default, but some layouts have full size in horizontal direction. You
can set the height, width, or both as undefined with the methods [methodname]#setWidthUndefined()#,
[methodname]#setHeightUndefined()#, and [methodname]#setHeightUndefined()#, respectively.

Always keep in mind that _a layout with undefined size may not contain components with defined relative size_, such as "full size", except in some special cases.
See <<dummy/../../../framework/layout/layout-settings#layout.settings.size,"Layout Size">> for details.

The <<components.features.sizeable.units.table>> table lists the available units and their codes defined in the [interfacename]#Sizeable# interface.

[[components.features.sizeable.units.table]]
.Size units
[cols="5,2,10", options="header"]
|===============
|Constant|Unit|Description
|[parameter]#Unit.PIXELS#|px|The _pixel_ is the basic hardware-specific measure of one physical display pixel.
|[parameter]#Unit.POINTS#|pt|The _point_ is a typographical unit, which is usually defined as 1/72 inches or about 0.35 mm. However, on displays the size can vary significantly depending on display metrics.
|[parameter]#Unit.PICAS#|pc|The _pica_ is a typographical unit, defined as 12 points, or 1/7 inches or about 4.233 mm. On displays, the size can vary depending on display metrics.
|[parameter]#Unit.EM#|em|A unit relative to the used font, the width of the upper-case "M" letter.
|[parameter]#Unit.EX#|ex|A unit relative to the used font, the height of the lower-case "x" letter.
|[parameter]#Unit.MM#|mm|A physical length unit, millimeters on the surface of a display device. However, the actual size depends on the display, its metrics in the operating system, and the browser.
|[parameter]#Unit.CM#|cm|A physical length unit, _centimeters_ on the surface of a display device. However, the actual size depends on the display, its metrics in the operating system, and the browser.
|[parameter]#Unit.INCH#|in|A physical length unit, _inches_ on the surface of a display device. However, the actual size depends on the display, its metrics in the operating system, and the browser.
|[parameter]#Unit.PERCENTAGE#|%|A relative percentage of the available size. For example, for the top-level layout [parameter]#100%# would be the full width or height of the browser window. The percentage value must be between 0 and 100.
|===============

If a component inside [classname]#HorizontalLayout# or [classname]#VerticalLayout# has full size in the namesake direction of the layout, the component will expand to take all available space not needed by the other components.
See <<dummy/../../../framework/layout/layout-settings#layout.settings.size,"Layout Size">> for details.

== Managing Input Focus

When the user clicks on a component, the component gets the __input focus__,
which is indicated by highlighting according to style definitions. If the
component allows inputting text, the focus and insertion point are indicated by
a cursor. Pressing the Tab key moves the focus to the component next in the
__focus order__.

Focusing is supported by all [classname]#Field# and [classname]#Select# components and also by
components such as [classname]#Button#, [classname]#Upload#, and [classname]#TabSheet#.

The focus order or __tab index__ of a component is defined as a positive integer
value, which you can set with [methodname]#setTabIndex()# and get with
[methodname]#getTabIndex()#. The tab index is managed in the context of the page
in which the components are contained. The focus order can therefore jump
between two any lower-level component containers, such as sub-windows or panels.

The default focus order is determined by the natural hierarchical order of
components in the order in which they were added under their parents. The
default tab index is 0 (zero).

Giving a negative integer as the tab index removes the component from the focus
order entirely.

=== CSS Style Rules

The component having the focus will have an additional style class with the
[literal]#++-focus++# suffix. For example, a [classname]#TextField#, which
normally has the [literal]#++v-textfield++# style, would additionally have the
[literal]#++v-textfield-focus++# style.

For example, the following would make a text field blue when it has focus.


[source, css]
----
.v-textfield-focus {
    background: lightblue;
}
----