Stylable Component Parts & States

Learn what stylable component parts and states are and how to use them when customizing the styles of Vaadin components.

Stylable Parts of Components
Component States
Component Style Variants

Various types of CSS selectors are used when applying custom CSS to Vaadin components. These can be divided into the parts that comprise the component, and the possible states of component parts.

Stylable Parts of Components

The various HTML elements that make up Vaadin components are listed on the Styling tab of each component documentation page. There are four primary types of parts, each of which is associated with a different type of CSS selector.

Root Elements

Each Vaadin component has a root HTML element whose name starts with the vaadin- prefix, such as vaadin-button or vaadin-combo-box.

vaadin-button {
  background: orange;
}

Shadow Parts

Shadow parts are elements inside the component’s shadow DOM and are styled using the ::part() selector. As an example, the input surface of a Text Field is styled using the input-field shadow part name:

vaadin-text-field::part(input-field) {
  background: white;
  border: 1px solid gray;
}

Some Vaadin components like Grid provide APIs that allow developers to apply their own part names to shadow parts like table cells based on custom logic.

Normal Child Elements

Normal HTML child elements are styled using the > selector. As an example, the Checkbox component’s label is a label element:

vaadin-checkbox > label {
  font-weight: bold;
}

Pseudo-Elements

The pseudo-elements ::before and ::after are elements generated with CSS. They are commonly used for font-based icons and highlight effects for states like hover and focus, often on one of the shadow parts rather than the root element. As an example, the Date Picker’s icon is a pseudo-element in the toggle-button shadow part, and its hover highlight is a pseudo-element on the input-field shadow part:

vaadin-date-picker::part(toggle-button)::before {
  color: blue;
}

vaadin-date-picker::part(input-field)::after {
  background-color: green;
}

Sub-Components

In addition to the above, many components utilize “sub-components” with their own root HTML elements. In many cases, these have their own shadow parts, child elements and pseudo-elements. As an example, the Date Picker’s overlay is a separate component with the root element vaadin-date-picker-overlay. Each month calendar in it is a vaadin-month-calendar component. They both contain various shadow parts.

vaadin-month-calendar::part(date) {
  font-weight: bold;
}

Component States

The various states of a Vaadin component are listed on the Styling tab of each component documentation page. There are three types of CSS selectors used for states: state attributes; state part-names; and pseudo classes. They’re each described below, as well as how to negate state selectors.

State Attributes

Most states of component root elements and their various parts are exposed through state attributes and styled using attribute selectors of the form component-name[state]. As an example, disabled Buttons are identified by the [disabled] selector:

vaadin-button[disabled] {
  background: lightgray;
  color: darkgray;
}

State attributes can be combined with part selectors by placing the attribute selector before the part, child or pseudo-element selector:

vaadin-text-field[disabled]::part(input-field) {
  border-color: lightgray;
}

vaadin-checkbox[disabled] > label {
  color: gray;
}

vaadin-date-picker[disabled]::part(toggle-button)::before {
  visibility: hidden;
}

State Part-Names

Some shadow parts have their own states exposed as additional part names. As an example, a disabled date in the Date Picker’s calendar is styled using the part names date and disabled, combined into the same ::part() selector:

vaadin-month-calendar::part(date disabled) {
  color: red;
}

Pseudo-Classes

Pseudo-classes are CSS features used for certain native HTML states like hover. They can be combined with any other selector:

vaadin-button:hover {
  border-color: blue;
}

vaadin-text-field[disabled]:hover::part(input-field) {
  border-color: red;
}

In the example above, the first style block applies a border color to Buttons on hover, and the second applies a red border color to the input surface of disabled Text Fields on hover.

Negating or Excluding States

To target the opposite of a state exposed as an attribute or a pseudo-class, the state selector can be wrapped in a :not() selector. This is often needed to exclude a particular state from a style block.

vaadin-button:not([disabled]) {
  border-color: blue;
}

Component Style Variants

Many Vaadin components come with built-in style variants, listed on the documentation page for each component, that can be used to change the color, size or other visual aspects of individual component instances through the addThemeVariants Java API.

Built-in style variants of the Button component

These variants are applied with theme attributes on the root elements of components, and can be targeted with CSS attribute selectors, and excluded by wrapping the attribute selector in a :not() selector.

vaadin-button[theme~="primary"] {
  background-color: orange;
}

vaadin-button:not([theme~="primary"]) {
  color: orange;
}

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Documentation