@material/dialog

MDC Dialog

The MDC Dialog component is a spec-aligned dialog component adhering to the Material Design dialog pattern. It implements a modal dialog window. You may notice that full screen components outlined in the dialog spec do not appear in MDC Dialog. This is because they have been deemed to be outside of the scope of what a dialog should be.

Installation

npm install --save @material/dialog

Dialog usage

Dialogs inform users about a specific task and may contain critical information or require decisions.

<aside id="my-mdc-dialog"
  style="visibility:hidden"
  class="mdc-dialog"
  role="alertdialog"
  aria-labelledby="my-mdc-dialog-label"
  aria-describedby="my-mdc-dialog-description">
  <div class="mdc-dialog__surface">
    <header class="mdc-dialog__header">
      <h2 id="my-mdc-dialog-label" class="mdc-dialog__header__title">
        Use Google's location service?
      </h2>
    </header>
    <section id="my-mdc-dialog-description" class="mdc-dialog__body">
      Let Google help apps determine location. This means sending anonymous location data to Google, even when no apps are running.
    </section>
    <footer class="mdc-dialog__footer">
      <button type="button" class="mdc-button mdc-dialog__footer__button mdc-dialog__footer__button--cancel">Decline</button>
      <button type="button" class="mdc-button mdc-dialog__footer__button mdc-dialog__footer__button--accept">Accept</button>
    </footer>
  </div>
  <div class="mdc-dialog__backdrop"></div>
</aside>

In the example above, we've created a dialog box in an aside element. Note that you can place content inside the dialog. There are two types: dialog & dialogs with scrollable content. These are declared using CSS classes.

Some dialogs will not be tall enough to accomodate everything you would like to display in them. For this there is a mdc-dialog__body--scrollable modifier to allow scrolling in the dialog.

  <aside id="mdc-dialog-with-list"
    style="visibility:hidden"
    class="mdc-dialog"
    role="alertdialog"
    aria-labelledby="mdc-dialog-with-list-label"
    aria-describedby="mdc-dialog-with-list-description">
    <div class="mdc-dialog__surface">
      <header class="mdc-dialog__header">
        <h2 id="mdc-dialog-with-list-label" class="mdc-dialog__header__title">
          Choose a Ringtone
        </h2>
      </header>
      <section id="mdc-dialog-with-list-description" class="mdc-dialog__body mdc-dialog__body--scrollable">
       	<ul class="mdc-list">
          <li class="mdc-list-item">None</li>
          <li class="mdc-list-item">Callisto</li>
          <li class="mdc-list-item">Ganymede</li>
          <li class="mdc-list-item">Luna</li>
          <li class="mdc-list-item">Marimba</li>
          <li class="mdc-list-item">Schwifty</li>
          <li class="mdc-list-item">Callisto</li>
          <li class="mdc-list-item">Ganymede</li>
          <li class="mdc-list-item">Luna</li>
          <li class="mdc-list-item">Marimba</li>
          <li class="mdc-list-item">Schwifty</li>
        </ul>
      </section>
      <footer class="mdc-dialog__footer">
        <button type="button" class="mdc-button mdc-dialog__footer__button mdc-dialog__footer__button--cancel">Decline</button>
        <button type="button" class="mdc-button mdc-dialog__footer__button mdc-dialog__footer__button--accept">Accept</button>
      </footer>
    </div>
    <div class="mdc-dialog__backdrop"></div>
  </aside>

Note that unlike the css classnames, the specific ID names used do not have to be exactly the same as listed above. They only need to match the values set for their corresponding aria attributes.

Using the Component

MDC Dialog ships with a Component / Foundation combo which allows for frameworks to richly integrate the correct dialog behaviors into idiomatic components.

Including in code

ES2015

import {MDCDialog, MDCDialogFoundation, util} from 'mdc-dialog';

CommonJS

const mdcDialog = require('mdc-dialog');
const MDCDialog = mdcDialog.MDCDialog;
const MDCDialogFoundation = mdcDialog.MDCDialogFoundation;
const util = mdcDialog.util;

AMD

require(['path/to/mdc-dialog'], mdcDialog => {
  const MDCDialog = mdcDrawer.MDCDialog;
  const MDCDialogFoundation = mdcDialog.MDCDialogFoundation;
  const util = mdcDialog.util;
});

Global

const MDCDialog = mdc.dialog.MDCDialog;
const MDCDialogFoundation = mdc.dialog.MDCDialogFoundation;
const util = mdc.dialog.util;

Automatic Instantiation

If you do not care about retaining the component instance for the temporary drawer, simply call attachTo() and pass it a DOM element. This however, is only useful if you do not need to pass a callback to the dialog when the user selects Accept or Cancel.

mdc.dialog.MDCDialog.attachTo(document.querySelector('#my-mdc-dialog'));

Manual Instantiation

Dialogs can easily be initialized using their default constructors as well, similar to attachTo.

import {MDCDialog} from 'mdc-dialog';

const dialog = new MDCDialog(document.querySelector('#my-mdc-dialog'));

Using the dialog component

var dialog = new mdc.dialog.MDCDialog(document.querySelector('#mdc-dialog-default'));

dialog.listen('MDCDialog:accept', function() {
  console.log('accepted');
})

dialog.listen('MDCDialog:cancel', function() {
  console.log('canceled');
})

document.querySelector('#default-dialog-activation').addEventListener('click', function (evt) {
  dialog.lastFocusedTarget = evt.target;
  dialog.show();
})

Dialog component API

MDCDialog.open

Boolean. True when the dialog is shown, false otherwise.

MDCDialog.show() => void

Shows the dialog

MDCDialog.close() => void

Closes the dialog

Dialog Events

MDCDialog:accept

Broadcast when a user actions on the .mdc-dialog__footer__button--accept element.

MDCDialog:cancel

Broadcast when a user actions on the .mdc-dialog__footer__button--cancel element.

Using the Foundation Class

MDC Dialog ships with an MDCDialogFoundation class that external frameworks and libraries can use to integrate the component. As with all foundation classes, an adapter object must be provided.

NOTE: Components themselves must manage adding ripples to dialog buttons, should they choose to do so. We provide instructions on how to add ripples to buttons within the mdc-button README.

Adapter API

Method Signature	Description
addClass(className: string) => void	Adds a class to the root element.
removeClass(className: string) => void	Removes a class from the root element.
setStyle(propertyName: string, value: string) => void	Sets a style property propertyName on the root element to the value specified
addBodyClass(className: string) => void	Adds a class to the body.
removeBodyClass(className: string) => void	Removes a class from the body.
eventTargetHasClass(target: EventTarget, className: string) => boolean	Returns true if target has className, false otherwise.
registerInteractionHandler(evt: string, handler: EventListener) => void	Adds an event listener to the root element, for the specified event name.
deregisterInteractionHandler(evt: string, handler: EventListener) => void	Removes an event listener from the root element, for the specified event name.
registerSurfaceInteractionHandler(evt: string, handler: EventListener) => void	Registers an event handler on the dialog surface element.
deregisterSurfaceInteractionHandler(evt: string, handler: EventListener) => void	Deregisters an event handler from the dialog surface element.
registerDocumentKeydownHandler(handler: EventListener) => void	Registers an event handler on the document object for a keydown event.
deregisterDocumentKeydownHandler(handler: EventListener) => void	Deregisters an event handler on the document object for a keydown event.
notifyAccept() => {}	Broadcasts an event denoting that the user has accepted the dialog.
notifyCancel() => {}	Broadcasts an event denoting that the user has cancelled the dialog.
trapFocusOnSurface() => {}	Sets up the DOM which the dialog is contained in such that focusability is restricted to the elements on the dialog surface (see Handling Focus Trapping below for more details).
untrapFocusOnSurface() => {}	Removes any affects of focus trapping on the dialog surface from the DOM (see Handling Focus Trapping below for more details).

Handling Focus Trapping

In order for dialogs to be fully accessible, they must conform to the guidelines outlined in https://www.w3.org/TR/wai-aria-practices/#dialog_modal. The main implication of these guidelines is that the only focusable elements are those contained within a dialog surface.

Trapping focus correctly for a modal dialog requires a complex set of events and interaction patterns that we feel is best not duplicated within the logic of this component. Furthermore, frameworks and libraries may have their own ways of trapping focus that framework authors may want to make use of. For this reason, we have two methods on the adapter that should be used to handle focus trapping:

• trapFocusOnSurface() is called when the dialog is open and should set up focus trapping adhering to the ARIA practices in the link above.
• untrapFocusOnSurface() is called when the dialog is closed and should tear down any focus trapping set up when the dialog was open.

In our MDCDialog component, we use the focus-trap package to handle this. You can use util.createFocusTrapInstance to easily create a focus trapping solution for your component code.

The full foundation API

MDCDialogFoundation.open() => void

Opens the dialog, registers appropriate event listeners, sets aria attributes, focuses elements.

MDCDialogFoundation.close() => void

Closes the dialog, deregisters appropriate event listeners, resets aria attributes, focuses elements.

MDCDialogFoundation.accept(notifyChange = false) => void

Closes the dialog. If notifyChange is true, calls the adapter's notifyAccept() method.

MDCDialogFoundation.cancel(notifyChange = false) => void

Closes the dialog. If notifyChange is true, calls the adapter's notifyCancel() method.

MDCDialogFoundation.isOpen() => Boolean

Returns true if the dialog is open, false otherwise.

MDCDialog Util API

util.createFocusTrapInstance(surfaceEl, acceptButtonEl, focusTrapFactory = require('focus-trap')) => {activate: () => {}, deactivate: () => {}};

Given a dialog surface element, an accept button element, and an optional focusTrap factory function, creates a properly configured focus-trap instance such that:

• The focus is trapped within the surfaceEl
• The acceptButtonEl receives focus when the focus trap is activated
• Pressing the escape key deactivates focus
• Clicking outside the dialog deactivates focus
• Focus is returned to the previously focused element before the focus trap was activated

This focus trap instance can be used to implement the trapFocusOnSurface and untrapFocusOnSurface adapter methods by calling instance.activate() and instance.deactivate() respectively within those methods.

The focusTrapFactory can be used to override the focus-trap function used to create the focus trap. It's API is the same as focus-trap's createFocusTrap (which is what it defaults to). You can pass in a custom function for mocking out the actual function within tests, or to modify the arguments passed to the function before it's called.

Theming - Dark Theme Considerations

When using mdc-theme--dark / mdc-dialog--theme-dark, the dialog by default sets its background color to #303030. You can override this by either overridding the --mdc-dialog-dark-theme-bg-color, overridding the $mdc-dialog-dark-theme-bg-color sass variable, or directly in CSS:

.mdc-theme--dark .mdc-dialog__surface,
.mdc-dialog--theme-dark .mdc-dialog__surface {
  background-color: /* custom bg color */;
}