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

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.

API

Ancestry: MenuButton → PopupSourceReactiveElement → HTMLElement

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

Includes subelements Backdrop, OverlayFrame, Popup, and Menu.

Extended by class DropdownList.

$ property

The collection of references to the elements with IDs 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.$.foo to obtain the corresponding button in the component instance's shadow tree.

Such references simplify a component's access to its own elements. In exchange, this mixin trades off a one-time cost of querying all elements in the shadow tree instead of paying an ongoing cost to query for an element each time the component wants to inspect or manipulate it.

These shadow element references are established the first time you read the $ property. They are not updated if you subsequently modify the shadow tree yourself (to replace one item with another, to add new items with id attributes, etc.).

Type: object

Defined by ShadowTemplateMixin inherited from ReactiveElement

backdropTag property

The tag used to create the optional backdrop element behind the overlay.

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: string

Default: 'elix-backdrop'

Inherited from 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 inherited from PopupSource

closed event

Raised when the component closes.

Defined by OpenCloseMixin inherited from PopupSource

closed property

True if the element is currently closed.

Type: boolean

Defined by OpenCloseMixin inherited from PopupSource

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 inherited from PopupSource

defaultState property

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

Type: object

Defined by ReactiveMixin inherited from ReactiveElement

frameTag property

The tag used to contain the popup 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: string

Default: 'elix-overlay-frame'

Inherited from PopupSource

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'

Inherited from PopupSource

menu-item-selected event

Raised when the user selects a menu item.

menuTag property

The tag used to define the menu.

The menu element is responsible for presenting the menu items and handling navigation between them.

Type: string

Default: 'elix-menu'

open() method

Open the element (if not already opened).

Defined by OpenCloseMixin inherited from PopupSource

opened event

Raised when the component opens.

Defined by OpenCloseMixin inherited from PopupSource

opened property

True if the element is currently closed.

Type: boolean

Defined by OpenCloseMixin inherited from PopupSource

opened-changed event

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

Defined by OpenCloseMixin inherited from 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'

Inherited from PopupSource

popupTag property

The tag used to define the popup.

The popup element is responsible for handling overlay behavior.

Type: string

Default: 'elix-popup'

Inherited from PopupSource

refineState(state) method

Apply changes to a proposed new state for the component to enforce necessary consistency between state members. See Refining state for details.

Parameters:
  • state: objecta proposed new state for the component

Returns: boolean - true if the state is already acceptable as it is

Defined by ReactiveMixin inherited from ReactiveElement

render() method

Render the component to the DOM.

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

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

Defined by ReactiveMixin inherited from ReactiveElement

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 inherited from ReactiveElement

shouldComponentUpdate(nextState) method

Return true if the component should update.

The default implementation does a shallow check of property values like React's PureComponent. This seems adequate for most web components. You can override this to always return true (like React's base Component class), or to perform more specific, deeper checks for changes in state.

Parameters:
  • nextState: objectthe proposed new state for the element

Returns: boolean - true if the component should update (rerender)

Defined by ReactiveMixin inherited from ReactiveElement

sourceTag property

The tag used to define the source button (or other element) that the popup will be positioned in relation to.

Type: string

Default: 'button'

Inherited from PopupSource

state property

The component's current state. The returned state object is immutable. To update it, invoke setState.

Type: object

Defined by ReactiveMixin inherited from ReactiveElement

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 inherited from PopupSource

symbols.keydown() method

See the symbols documentation for details.

Defined by KeyboardMixin inherited from PopupSource

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 inherited from PopupSource

updates property

The attributes and properies that should be applied to the component on render. By default, this is an empty plain object. Your mixin or component can extend this to identify the properties to set on the host element or elements in the shadow subtree.

Type: object

Defined by RenderUpdatesMixin inherited from ReactiveElement

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 inherited from PopupSource