MenuButton

A button that invokes a menu
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Demo: A MenuButton can be used to provide access to less frequently-used commands

Overview

MenuButton is a button that invokes a menu. By default, clicking the button invokes an instance of Menu. You can customize that by setting the menuTag property.

MenuButton is a rather general base class for creating buttons that invoke menus, and as such does not itself do any work in response to selections the user may make from the menu. For a version of MenuButton optimized for selecting a single item from a list of choices, see DropdownList.

Mouse support

MenuButton lets a user select a command with the mouse in two ways:

  1. Select a menu item with two separate clicks. The first click opens the menu; the second picks a command from the menu. To cancel the operation, the user can click outside the menu.

  2. Select a menu item in a single drag operation. The user mouses down on the menu button, which opens the menu underneath the mouse. Keeping the mouse button down, the user drags into the menu. The menu tracks the selection under their mouse. The user releases the mouse to select a command. To cancel the operation, the user can move the mouse off the menu and release the mouse. (The operation will also be canceled if the user releases the mouse over a disabled menu item or menu separator.)

Keyboard support

When the MenuButton has focus and the menu is closed, the user can open the menu by pressing Space or the Up or Down arrow keys.

When the menu is open, the user can move the selection with the arrow keys, Home, End, Page Up, or Page Down. They can also type the letters that begin a command's text. The user can select a command and close the menu by pressing Enter, or dismiss the menu by pressing Esc.

By default, MenuButton displays the items in a Menu which, when open, will give the keyboard focus to the currently-selected item.

See also

DropdownList
Shows a single choice made from a pop-up list of choices
Menu
A menu of choices or commands

API

Ancestry: MenuButton → PopupButtonPopupSourceReactiveElement → HTMLElement

Built with mixins AriaRoleMixin, AttributeMarshallingMixin, DisabledMixin, FocusVisibleMixin, KeyboardMixin, KeyboardMixin, OpenCloseMixin, ReactiveMixin, and ShadowTemplateMixin.

The element defines the following shadow parts:

  • backdrop: the backdrop behind the overlay, default type is Hidden
  • frame: the frame around the overlay, default type is OverlayFrame
  • menu: the menu shown in the popup, default type is Menu
  • popup: the popup element, default type is Popup
  • source: the element used as the reference point for positioning the popup, generally the element that invokes the popup, default type is div element
  • toggle-icon: icon shown in the button that invokes the menu

Extended by class DropdownList.

backdropPartType property

The class, tag, or template used for the backdrop part - the optional element shown behind the popup.

This can help focus the user's attention on the overlay content. Additionally, a backdrop can be used to absorb clicks on background page elements. For example, Dialog uses ModalBackdrop as an overlay backdrop in such a way.

Type: (component class constructor)|HTMLTemplateElement|string

Default: Backdrop

Defined by PopupSource

close(closeResult) method

Close the component (if not already closed).

Some components like AlertDialog want to indicate why or how they were closed. To support such scenarios, you can supply a value to the optional closeResult parameter. This closeResult will be made available in the whenClosed promise and the state.closeResult member.

Parameters:

  • closeResult: objectan indication of how or why the element closed

Defined by OpenCloseMixin

closed property

True if the element is currently closed.

Type: boolean

Defined by OpenCloseMixin

closed event

Raised when the component closes.

Defined by OpenCloseMixin

closeFinished property

True if the element has completely closed.

For components not using asynchronous open/close effects, this property returns the same value as the closed property. For elements that have a true value of state.openCloseEffects (e.g., elements using TransitionEffectMixin), this property returns true only if state.effect is "close" and state.effectPhase is "after".

Type: boolean

Defined by OpenCloseMixin

disabled property

True if the component is disabled, false (the default) if not.

The value of this property will be reflected to the disabled attribute so that it can be referenced in CSS. Note that this non-native implementation of the disabled attribute will not trigger the :disabled CSS pseudo-class, so your style rules will have to reference the presence or absence of the disabled attribute. That is, instead of writing

my-component:disabled { ... }

write this instead

my-component[disabled] { ... }

Like the native disabled attribute, this attribute is boolean. That means that it's existence in markup sets the attribute, even if set to an empty string or a string like "false".

Type: boolean

Default: false

Defined by DisabledMixin

framePartType property

The class, tag, or template used to create the frame part – the popup's primary content.

The frame element can be used to provide a border around the popup content, and to provide visual effects such as a drop-shadow to help distinguish popup content from background page elements.

Type: (component class constructor)|HTMLTemplateElement|string

Default: OverlayFrame

Defined by PopupSource

highlightSelectedItemAndClose() method

Highlight the selected item (if one exists), then close the menu.

horizontalAlign property

The alignment of the popup with respect to the source button.

  • start: popup and source are aligned on the leading edge according to the text direction
  • end: popup and source are aligned on the trailing edge according to the text direction
  • left: popup and source are left-aligned
  • right: popup and source are right-aligned
  • `stretch: both left and right edges are aligned

Type: 'start'|'end'|'left'|'right'|'stretch'

Default: 'start'

Defined by PopupSource

[internal.defaultState] property

The default state for the component. This can be extended by mixins and classes to provide additional default state.

Type: State

Defined by ReactiveMixin

[internal.ids] property

A convenient shortcut for looking up an element by ID in the component's Shadow DOM subtree.

Example: if component's template contains a shadow element <button id="foo">, you can use the reference this[internal.ids].foo to obtain the corresponding button in the component instance's shadow tree. The ids property is simply a shorthand for getElementById, so this[internal.ids].foo is the same as this.shadowRoot.getElementById('foo').

Type: object

Defined by ShadowTemplateMixin

[internal.keydown]() method

See the symbols documentation for details.

Defined by KeyboardMixin

[internal.render](changed) method

Render the indicated changes in state to the DOM.

The default implementation of this method does nothing. Override this method in your component to update your component's host element and any shadow elements to reflect the component's new state. See the rendering example.

Be sure to call super in your method implementation so that your component's base classes and mixins have a chance to perform their own render work.

Parameters:

  • changed: objectdictionary of flags indicating which state members have changed since the last render

Defined by ReactiveMixin

[internal.renderChanges]() method

Render any pending component changes to the DOM.

This method does nothing if the state has not changed since the last render call.

ReactiveMixin will invoke this method following a setState call; you should not need to invoke this method yourself.

This method invokes all internal render methods, then invokes componentDidMount (for first render) or componentDidUpdate (for subsequent renders).

Defined by ReactiveMixin

[internal.setState](changes) method

Update the component's state by merging the specified changes on top of the existing state. If the component is connected to the document, and the new state has changed, this returns a promise to asynchronously render the component. Otherwise, this returns a resolved promise.

Parameters:

  • changes: objectthe changes to apply to the element's state

Returns: Promise - resolves when the new state has been rendered

Defined by ReactiveMixin

[internal.state] property

The component's current state.

The returned state object is immutable. To update it, invoke internal.setState.

It's extremely useful to be able to inspect component state while debugging. If you append ?elixdebug=true to a page's URL, then ReactiveMixin will conditionally expose a public state property that returns the component's state. You can then access the state in your browser's debug console.

Type: State

Defined by ReactiveMixin

itemSelected(item) method

Invoked when a new item is selected.

Parameters:

  • item: HTMLElement|SVGElement

menu-item-selected event

Raised when the user has moved the selection to a new menu item. This event is raised while the menu is still open. To check which item the user selected from a menu, listen to the closed event and inspect the event details object for its closeResult member.

menuPartType property

The class, tag, or template used to define the menu part – the element presenting the menu items and handling navigation between them.

Type: (component class constructor)|HTMLTemplateElement|string

Default: Menu

open() method

Open the element (if not already opened).

Defined by OpenCloseMixin

opened property

True if the element is currently opened.

Type: boolean

Defined by OpenCloseMixin

opened event

Raised when the component opens.

Defined by OpenCloseMixin

opened-changed event

Raised when the opened/closed state of the component changes.

Defined by OpenCloseMixin

popupPartType property

The class, tag, or template used to create the popup part – the element responsible for displaying the popup and handling overlay behavior.

Type: (component class constructor)|HTMLTemplateElement|string

Default: Popup

Defined by PopupSource

popupPosition property

The preferred direction for the popup.

  • above: popup should appear above the source
  • below: popup should appear below the source

Type: 'above'|'below'

Default: 'below'

Defined by PopupSource

sourcePartType property

The class, tag, or template used to create the source part - the button (or other element) the user can tap/click to invoke the popup.

Type: (component class constructor)|HTMLTemplateElement|string

Default: 'button'

Defined by PopupSource

suppressFocusVisibility() method

Temporarily suppress visibility of the keyboard focus until the next keydown event.

This can be useful in components like Menu that actively manage where the focus is in response to mouse hover activity. If the user uses the keyboard to invoke a menu, then changes to using the mouse, it can be distracting to see the focus indicator moving as well. In such situations, the component can invoke this method (e.g., in response to mousemove) to temporarily suppress focus visibility.

Defined by FocusVisibleMixin

toggle(opened) method

Toggle the open/close state of the element.

Parameters:

  • opened: booleantrue if the element should be opened, false if closed.

Defined by OpenCloseMixin

whenClosed() method

This method can be used as an alternative to listening to the "opened-changed" event, particularly in situations where you want to only handle the next time the component is closed.

Returns: Promise A promise that resolves when the element has completely closed, including the completion of any asynchronous opening effect.

Defined by OpenCloseMixin