Mixin: module:delite/KeyNav

module:delite/KeyNav

A mixin to allow arrow key and letter key navigation of child Elements. It can be used by delite/Container based widgets with a flat list of children, or more complex widgets like a Tree.

To use this mixin, the subclass must:

  • Implement one method for each keystroke that the subclass wants to handle. The methods for up and down arrow keys are upKeyHandler() anddownKeyHandler(). For BIDI support, the left and right arrows are handled specially, mapped to thepreviousKeyHandler()andnextKeyHandler()methods in LTR mode, or reversed in RTL mode. Otherwise, the method name is based on the key names defined by https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/key, for examplehomeKeyHandler(). The method takes two parameters: the event, and the currently navigated node. Most subclasses will want to implement eitherpreviousKeyHandler()andnextKeyHandler(), ordownKeyHandler()andupKeyHandler()`.
  • Set all navigable descendants' initial tabIndex to "-1"; both initial descendants and any descendants added later, by for example addChild(). Exception: if focusDescendants is false then the descendants shouldn't have any tabIndex at all.
  • Define descendantSelector as a function or string that identifies navigable child Elements.
  • If the descendant elements contain text, they should have a label attribute. KeyNav uses the label attribute for letter key navigation.
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Extends

Show inherited

Members

<protected> attached :boolean

Set to true when attachedCallback() has completed, and false when detachedCallback() called.

Type:
  • boolean
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<protected> baseClass :string

Root CSS class of the widget (ex: "d-text-box")

Type:
  • string
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<protected> created :boolean

Set to true when createdCallback() has completed.

Type:
  • boolean
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<protected, constant> descendantSelector :string|function

Selector to identify which descendant Elements are navigable via arrow keys or keyboard search. Note that for subclasses like a Tree, one navigable node could be a descendant of another.

It's either a function that takes an Element parameter and returns true/false, or a CSS selector string, for example ".list-item".

By default, the direct DOM children of this widget are considered the selectable descendants.

Must be set in the prototype rather than on the instance.

Type:
  • string | function
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dir :string

Controls the layout direction of the widget, for example whether the arrow of a Combobox appears to the right or the left of the input field.

Values are "ltr" and "rtl", or "" which means that the value is inherited from the setting on the document root (either <html> or <body>).

Type:
  • string
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<readonly> effectiveDir :string

Actual direction of the widget, which can be set explicitly via dir property or inherited from the setting on the document root (either <html> or <body>). Value is either "ltr" or "rtl".

Type:
  • string
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<protected> focusDescendants :boolean

When true, focus the descendant widgets as the user navigates to them via arrow keys or keyboard letter search. When false, rather than focusing the widgets, it merely sets navigatedDescendant, and sets the d-active-descendant class on the descendant widget the user has navigated to.

False mode is intended for widgets like ComboBox where the focus is somewhere outside this widget (typically on an <input>) and keystrokes are merely being forwarded to the KeyNav widget.

When set to false:

  • All navigable descendants must specify an id.
  • Navigable descendants shouldn't have any tabIndex (as opposed to having tabIndex=-1).
  • The focused element should specify aria-owns to point to this KeyNav Element.
  • The focused Element must be kept synced so that aria-activedescendant points to the currently navigated descendant. Do this responding to the keynav-child-navigated event emitted by this widget, or by calling observe() and monitoring changed to navigatedDescendant.
  • The focused Element must forward keystrokes by calling emit("keydown", ...) and/or emit("keypress", ...) on this widget.
  • You must somehow set the initial navigated descendant, typically by calling navigateToFirst() either when the the dropdown is opened, or on the first call to downKeyHandler().
  • You must have some CSS styling so that the currently navigated node is apparent.

See http://www.w3.org/WAI/GL/wiki/Using_aria-activedescendant_to_allow_changes_in_focus_within_widgets_to_be_communicated_to_Assistive_Technology#Example_1:_Combobox for details.

Type:
  • boolean
Default Value:
  • true
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<protected> focused :boolean

This widget or a widget it contains has focus, or is "active" because it was recently clicked.

Type:
  • boolean
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Default Value:
  • false
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The currently navigated descendant, or null if there isn't one.

Type:
  • Element
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<protected> template :function

Value returned by delite/handlebars! or compatible template engine. Specifies how to build the widget DOM initially and also how to update the DOM when widget properties change.

Type:
  • function
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<protected, constant> widgetId :number

Unique id for this widget, separate from id attribute (which may or may not be set). Useful when widget creates subnodes that need unique id's.

Type:
  • number
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Methods

<protected> _get(name) → {*}

Internal helper for directly accessing an attribute value.

Directly gets the value of an attribute on an object, bypassing any accessor getter. It is designed to be used by descendant class if they want to access the value in their custom getter before returning it.

Parameters:
Name Type Description
name string

Name of property.
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Returns:

Value of property.

Type
*

<protected> _set(name, value)

Internal helper for directly setting a property value without calling the custom setter.

Directly changes the value of an attribute on an object, bypassing any accessor setter. Also notifies callbacks registered via observe(). Custom setters should call _set to actually record the new value.

Parameters:
Name Type Description
name string

The property to set.
value *

Value to set the property to.
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attachedCallback()

Called automatically when the element is added to the document, after createdCallback() completes. This method is automatically chained, so subclasses generally do not need to use dcl.superCall(), dcl.advise(), etc.

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computeProperties(oldValues, isAfterCreation)

Callback function to calculate computed properties upon property changes.

Parameters:
Name Type Description
oldValues Object

The hash table of old property values, keyed by property names.
isAfterCreation boolean

True if this call is right after instantiation.
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<protected> createdCallback()

Called when the custom element is created, or when register.parse() parses a custom tag.

This method is automatically chained, so subclasses generally do not need to use dcl.superCall(), dcl.advise(), etc.

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<protected> defer(fcn, delay) → {Object}

Wrapper to setTimeout to avoid deferred functions executing after the originating widget has been destroyed.

Parameters:
Name Type Description
fcn function

Function to be executed after specified delay (or 0ms if no delay specified).
delay number

Delay in ms, defaults to 0.
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Returns:

Handle with a remove method that deschedules the callback from being called.

Type
Object

deliver()

Synchronously deliver change records to all listeners registered via observe().

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deliverComputing()

Synchronously deliver change records for computed properties so that computeProperties() is called if there are pending change records.

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destroy()

Release resources used by this custom element and its descendants. After calling this method, the element can no longer be used, and should be removed from the document.

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detachedCallback()

Called when the element is removed the document. This method is automatically chained, so subclasses generally do not need to use dcl.superCall(), dcl.advise(), etc.

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discardChanges()

Discard change records for all listeners registered via observe().

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discardComputing()

Discard change records for computed properties.

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<protected> emit(type, eventObj) → {boolean}

Emits a synthetic event of specified type, based on eventObj.

Parameters:
Name Type Argument Description
type string

Name of event.
eventObj Object <optional>

Properties to mix in to emitted event. Can also contain bubbles and cancelable properties to control how the event is emitted.
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Returns:

True if the event was not canceled, false if it was canceled.

Type
boolean
Example
myWidget.emit("query-success", {});

<protected> endKeyHandler(evt, navigatedDescendant)

Called on end key.

Parameters:
Name Type Description
evt Event
navigatedDescendant Element
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findCustomElements(root)

Search subtree under root returning custom elements found.

Parameters:
Name Type Argument Description
root Element <optional>

Node to search under.
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focus()

/** Default focus() implementation: navigate to the first navigable descendant. Note that if focusDescendants is false, this will merely set the d-active-descendant class rather than actually focusing the descendant.

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getEnclosingWidget(node)

Returns the widget whose DOM tree contains the specified DOMNode, or null if the node is not contained within the DOM tree of any widget

Parameters:
Name Type Description
node Element
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<protected> getInheritedDir() → {string}

Get the direction setting for the page itself.

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Returns:

"ltr" or "rtl"

Type
string

<protected> getNext(child, dir) → {Element}

Returns the next or previous navigable descendant, relative to "child". If "child" is this, then it returns the first focusable descendant (when dir === 1) or last focusable descendant (when dir === -1).

Parameters:
Name Type Description
child Element

The current child Element.
dir number

1 = after, -1 = before
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Returns:
Type
Element

getParent()

Returns the parent widget of this widget, or null if there is no parent widget.

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<protected> getProps() → {Object}

Returns a hash of properties that should be observed.

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Returns:

Hash of properties.

Type
Object

<protected> getPropsToObserve() → {Array.<string>}

Get list of properties that Stateful#observe() should observe.

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Returns:

list of properties

Type
Array.<string>

<protected> homeKeyHandler(evt, navigatedDescendant)

Called on home key.

Parameters:
Name Type Description
evt Event
navigatedDescendant Element
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<protected> initializeInvalidating()

Make initial calls to computeProperties(), initializeRendering(), and refreshRendering(), and setup observers so those methods are called whenever properties are modified in the future. Normally this method is called automatically by the constructor, and should not be called manually, but the method is exposed for custom elements since they do not call the constructor() method.

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initializeRendering(oldValues)

Callback function to initialize rendering.

Parameters:
Name Type Description
oldValues Object

The hash table of old property values, keyed by property names.
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<protected> introspect(props)

Sets up ES5 getters/setters for each class property. Inside introspect(), "this" is a reference to the prototype rather than any individual instance.

Parameters:
Name Type Description
props Object

Hash of properties.
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mix(hash)

Set a hash of properties on a Stateful instance.

Parameters:
Name Type Description
hash Object

Hash of properties.
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Example
myObj.mix({
    foo: "Howdy",
    bar: 3
});

Navigate to the specified descendant. Note that if focusDescendants is false, this will merely set the d-active-descendant class rather than actually focusing the descendant.

Parameters:
Name Type Argument Description
child Element

Reference to the descendant.
last boolean <optional>

If true and if descendant has multiple focusable nodes, focus the last one instead of the first one. This assumes that the child's focus() method takes a boolean parameter where true means to focus the last child.
triggerEvent Event <optional>

The event that lead to the navigation, or undefined if the navigation is triggered programmatically.
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Navigate to the first navigable descendant. Note that if focusDescendants is false, this will merely set the d-active-descendant class rather than actually focusing the descendant.

Parameters:
Name Type Argument Description
triggerEvent Event <optional>

The event that lead to the navigation, or undefined if the navigation is triggered programmatically.
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Navigate to the last navigable descendant. Note that if focusDescendants is false, this will merely set the d-active-descendant class rather than actually focusing the descendant.

Parameters:
Name Type Argument Description
triggerEvent Event <optional>

The event that lead to the navigation, or undefined if the navigation is triggered programmatically.
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notifyCurrentValue(name)

Notifies current values to observers for specified property name(s). Handy to manually schedule invocation of observer callbacks when there is no change in value.

Parameters:
Name Type Argument Description
name string <repeatable>

The property name.
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observe(callback) → {module:decor/Stateful.PropertyListObserver}

Observes for change in properties. Callback is called at the end of micro-task of changes with a hash table of old values keyed by changed property. Multiple changes to a property in a micro-task are squashed.

Parameters:
Name Type Description
callback function

The callback.
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Returns:

The observer that can be used to stop observation or synchronously deliver/discard pending change records.

Type
module:decor/Stateful.PropertyListObserver
Example
var stateful = new (dcl(Stateful, {
        foo: undefined,
        bar: undefined,
        baz: undefined
    }))({
        foo: 3,
        bar: 5,
        baz: 7
    });
stateful.observe(function (oldValues) {
    // oldValues is {foo: 3, bar: 5, baz: 7}
});
stateful.foo = 4;
stateful.bar = 6;
stateful.baz = 8;
stateful.foo = 6;
stateful.bar = 8;
stateful.baz = 10;

on(type, func, node) → {Object}

Call specified function when event occurs.

Note that the function is not run in any particular scope, so if (for example) you want it to run in the element's scope you must do myCustomElement.on("click", myCustomElement.func.bind(myCustomElement)).

Note that delite/Widget overrides on() so that on("focus", ...) and `on("blur", ...) will trigger the listener when focus moves into or out of the widget, rather than just when the widget's root node is focused/blurred. In other words, the listener is called when the widget is conceptually focused or blurred.

Parameters:
Name Type Argument Description
type string

Name of event (ex: "click").
func function

Callback function.
node Element <optional>

Element to attach handler to, defaults to this.
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Returns:

Handle with remove() method to cancel the event.

Type
Object

<protected> own() → {Array.<Object>}

Track specified handles and remove/destroy them when this instance is destroyed, unless they were already removed/destroyed manually.

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Returns:

The array of specified handles, so you can do for example: var handle = this.own(on(...))[0];

Type
Array.<Object>

<protected> parseAttribute(name, value)

Helper for parsing declarative widgets. Interpret a given attribute specified in markup, returning either:

  • undefined: ignore
  • {prop: prop, value: value}: set this[prop] = value
  • {event: event, callback: callback}: call this.on(event, callback)
Parameters:
Name Type Description
name string

Attribute name.
value string

Attribute value.
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<protected> parseFunctionAttribute(value, params)

Helper to parse function attribute in markup. Unlike _parsePrototypeAttr(), does not require a corresponding widget property. Functions can be specified as global variables or as inline javascript:

Parameters:
Name Type Description
value string

Value of the attribute.
params Array.<string>

When generating a function from inline javascript, give it these parameter names.
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<protected> placeAt(reference, position) → {module:delite/Widget}

Place this widget somewhere in the dom, and allow chaining.

Parameters:
Name Type Argument Description
reference string | Element | DocumentFragment

Element, DocumentFragment, or id of Element to place this widget relative to.
position string | number <optional>

Numeric index or a string with the values:

  • number - place this widget as n'th child of reference node
  • "first" - place this widget as first child of reference node
  • "last" - place this widget as last child of reference node
  • "before" - place this widget as previous sibling of reference node
  • "after" - place this widget as next sibling of reference node
  • "replace" - replace specified reference node with this widget
  • "only" - replace all children of reference node with this widget
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Returns:

This widget, for chaining.

Type
module:delite/Widget
Examples
// create a Button with no srcNodeRef, and place it in the body:
var button = new Button({ label:"click" }).placeAt(document.body);
// place a new button as the first element of some div
var button = new Button({ label:"click" }).placeAt("wrapper","first");
// create a contentpane and add it to a TabContainer
var tc = document.getElementById("myTabs");
new ContentPane({ href:"foo.html", title:"Wow!" }).placeAt(tc)

<protected> postRender()

Processing after the DOM fragment is created.

Called after the DOM fragment has been created, but not necessarily added to the document. Do not include any operations which rely on node dimensions or placement.

This method is automatically chained, so subclasses generally do not need to use dcl.superCall(), dcl.advise(), etc.

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<protected> preRender()

Processing before render().

This method is automatically chained, so subclasses generally do not need to use dcl.superCall(), dcl.advise(), etc.

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<protected> processConstructorParameters()

Called after Object is created to process parameters passed to constructor.

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refreshRendering(oldValues, isAfterInitialRendering)

Callback function to render UI upon property changes.

Parameters:
Name Type Description
oldValues Object

The hash table of old property values, keyed by property names.
isAfterInitialRendering boolean

True if this call is right after initializeRendering().
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<protected> render()

Construct the UI for this widget, filling in subnodes and/or text inside of this. Most widgets will leverage delite/handlebars! to set template, rather than defining this method.

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<protected> setClassComponent(component, value, node)

Helper method to set a class (or classes) on a given node, removing the class (or classes) set by the previous call to setClassComponent() for the specified component and node. Used mainly by template.js to set classes without overwriting classes set by the user or other code (ex: CssState).

Parameters:
Name Type Argument Description
component string

Specifies the category.
value string

Class (or classes) to set.
node HTMLElement <optional>

The node to set the property on; defaults to widget root node.
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<protected> setOrRemoveAttribute(node, name, value)

Helper method to set/remove an attribute based on the given value:

  • If value is undefined, the attribute is removed. Useful for attributes like aria-valuenow.
  • If value is boolean, the attribute is set to "true" or "false". Useful for attributes like aria-selected.
  • If value is a number, it's converted to a string.
Parameters:
Name Type Description
node Element

The node to set the property on.
name string

Name of the property.
value string

Value of the property.
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shouldInitializeRendering(oldValues, isAfterCreation) → {boolean}

Function to return if rendering should be initialized. (Instead of making partial changes for post-initialization)

Parameters:
Name Type Description
oldValues Object

The hash table of old property values, keyed by property names.
isAfterCreation boolean

True if this call is right after instantiation.
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Returns:

True if rendering should be initialized.

Type
boolean

Events

customelement-attached

Dispatched after the CustomElement has been attached. This is useful to be notified when an HTMLElement has been upgraded to a CustomElement and attached to the DOM, in particular on browsers supporting native Custom Element.

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Example
element.addEventListener("customelement-attached", function (evt) {
     console.log("custom element: "+evt.target.id+" has been attached");
});

keynav-child-navigated

Dispatched after the user has selected a different descendant, by clicking, arrow keys, or keyboard search.

Properties:
Name Type Description
oldValue number

The previously selected item.
newValue number

The new selected item.
Source:
Example
widget.on("keynav-child-navigated", function (evt) {
	console.log("old value: " + evt.oldValue);
	console.log("new value: " + evt.newValue);
}