IndieUI: Events 1.0 is an abstraction between physical, device-specific user interaction events and inferred user intent such as scrolling or changing values. This provides an intermediate layer between device- and modality-specific user interaction events, and the basic user interface functionality used by web applications. IndieUI: Events focuses on granular user interface interactions such as scrolling the view, canceling an action, changing the value of a user input widget, selecting a range, placing focus on an object, etc. Implementing platforms will combine modality-specific user input, user idiosyncratic heuristics to determine the specific corresponding Indie UI event, and send that to the web application in addition to the modality-specific input such as mouse or keyboard events, should applications wish to process it.

See the introduction for background and usage examples.

Introduction

Background

Scripting usable interfaces can be difficult, especially when one considers that user interface design patterns differ across software platforms, hardware, and locales, and that those interactions can be further customized based on personal preference. Individuals are accustomed to the way the interface works on their own system, and their preferred interface frequently differs from that of the web application author's preferred interface.

For example, web application authors, wishing to intercept a user's intent to "zoom in" on a custom image viewer or map view, need to "listen" for all of the following events:

In addition to the general user interface challenges, custom interfaces often don't take into account users who access web content via assistive technologies that use alternate forms of input such as screen readers, switch interfaces, or speech-based command and control interfaces.

For example, a web page author may script a custom interface to look like a slider (e.g. one styled to look like an HTML "range" input) and behave like a slider when using standard mouse-based input, but there is no standard way for the value of the slider to be controlled programmatically, so the control may not be usable without a mouse or other pointer-based input.

It would be simpler to listen for a normalized request to "zoom in" on the current view, whereby the web application could determine the new scale factor and update its custom view accordingly. Whether through continuous physical events like a scroll wheel or discrete physical events like the keyboard shortcuts, a user could indicate his intent to "zoom in" and the web application author would only need to listen for a single type of event: zoomrequest.

IndieUI Events defines a way for web authors to register for these request events on a leaf node element or on a ancestor element acting as an event delegate. Authors also declaritively define which actions or behaviors a view responds to, and when it is appropriate for browsers to initiate these events.

Goals

The primary goals of the Events Module specification are declared as the following:

  1. Make it easier for web developers to author consistently usable interfaces that are input-agnostic and independent of a user's particular platform, hardware, locale, and preferences.
  2. Enable every type of control in these interfaces to be programmatically determinable and controllable by both mainstream and alternate forms of user input.

The IndieUI Working Group also hopes to provide a clear path for web developers to smoothly transition from currently existing physical events to IndieUI events, during the period when implementations of IndieUI are incomplete. This will likely be achieved through polyfill implementations in common JavaScript libraries, though such implementations are not a required deliverable of the IndieUI Working Group, and documentation of this development path is not a requirement of this Events Module specification.

Document Scope

Decisions regarding which specific physical user interactions (keyboard combinations, gestures, speech, etc.) trigger IndieUI events are explicitly listed as out-of-scope in the Working Group charter. User interface interaction patterns should be designed and defined by each operating system, rather than defined as part of any technical specification.

However, this document lists informative examples of certain keyboard and mouse events that may trigger each IndieUI event. They are listed here purely to aid in clarifying the reader's conceptual understanding of each event, as well as illustrating certain UI differences between platforms. These informative examples are primarily limited to keyboard and mouse events, because those physical modalities have been common in software interaction for decades, and their use is familiar to most readers.

For example, it may be common for the ESC key to trigger a "dismissrequest" event to close a dialog on most systems, but the specification does not require the user agent to use any particular physical event. It is an implementation detail, and left for the developers of each platform or assistive technology to determine whether ESC or some other interaction is the most appropriate way to trigger the "dismissrequest" event. As long as there is a documented way for end users to initiate each event, the user agent will be considered a conforming implementation.

Usage Examples

Dismissing a Modal Dialog

The following example uses a "dismissrequest" event to close or cancel out of a modal application dialog.

						<!-- Declare which IndieUI event(s) this element receives. -->
						<dialog uiactions="dismiss" id="myDialog">
						  ...
						</dialog>
						
						<script type="text/javascript">
						  
						  var myDialog = document.getElementById("myDialog");
						  
						  // Register the event at initialization.
						  // Option #1: On the receiver itself... See next example for Option #2.
						  myDialog.addEventListener("dismissrequest", dismissHandler);
						
						  // At some point during runtime, the handler will be called.
						  // For example, if the user presses ESC key while focus is inside the dialog.
						  function dismissHandler(e) {
						  
						    // Cancel and close the dialog. Don't forget to move focus before closing.
						    closeDialog(e.receiver); // Event.receiver is a readonly property like Event.target 
						    
						    // Then cancel the event.
						    e.stopPropagation(); // Stop the event from bubbling.
						    e.preventDefault(); // Let the UA/AT know the event was intercepted successfully.

						  }
						</script>
					

Changing the Value of a Custom Slider

The following example uses a "valuechangerequest" event to modify the value of a custom ARIA slider.

This example was cut. It needs to be rewritten once we add support for composite widgets with triggers or controllers (so the slider thumb can update the value via pointer-based events). See IndieUI-action-79.

Backwards-Compatibility

One of the core principles behind UI Change Request Events is that they operate on a backwards-compatible, opt-in basis. In other words, the web application author has to first be aware of these events, then explicitly declare each event receiver and register an event listener, or user agents behave as normal and do not initiate these events.

Change request events do not cause any direct manipulation or mutation of the DOM, and do not have any "default action" in the context of a web view. Instead, the event conveys the user's intent to the web application, and allows the web application to perform the appropriate action on behalf of the user, including making potential changes to the DOM. If a web application is authored to understand the change request event, it can cancel the event, which informs the user agent that the event has been captured and understood. If a web application does not cancel the event, the user agent may attempt fallback behavior or communicate to the user that the input has not been recognized.

UI Actions

User interface actions are declared as enumerated token attribute values on an element. Each value corresponds to a specific UI Request Event, and declares the web page author's ability to receive and handle each of the request events initiated by the user agent. In order to receive each request event, authors MUST also register for the event using Element.addEventListener() at this node or higher in the DOM. User agents SHOULD NOT initiate a UI Request Event when the user's point-of-regard is not inside an element with the corresponding defined action.

The uiactions IDL Attribute

The uiactions attribute of each instance of the Element interface MUST return a DOMTokenList reflecting the uiactions content attribute.

readonly attribute DOMTokenList uiactions
A DOM element attribute whose DOMTokenList value reflects the value of the uiactions content attribute.

This attribute is readonly b/c DOMTokenList values are modified by methods (e.g. el.uiactions.add("pan");) rather than by string assignment (e.g. NOT el.uiactions = "pan";). Need to make sure this is clear for authors.

The uiactions Content Attribute

Every element may have a uiactions attribute specified, which is necessary to define the receiver of each type of request event. The attribute, if specified, must have a value that is a set of whitespace-separated tokens representing the various actions to which the web application responds on behalf of this element. The actions that an element has assigned to it consists of all the tokens returned when the value of the uiactions attribute is split on whitespace. (Duplicates are ignored.)

User agents MUST reflect the uiactions content attribute in the uiactions IDL attribute.

					<!-- Body element is event listener for all events, but event receiver only for "delete" actions. -->
					<body uiactions="delete">
					
					  <!-- Element container for custom "mapview" is the event receiver for "pan" and "zoom" actions. -->
					  <div id="mapview" uiactions="pan zoom"> ... </div>
					
					  <!-- This Dialog is the event receiver for "dismiss" actions initiated on any lower-level event target. -->
					  <dialog uiactions="dismiss"> ... </dialog>
					
					</body>
					
					<script type="text/javascript">
					  // Registered all of these on the body as an example of event delegation to help illustrate the difference between event...
					  // ...target (document.activeElement or other point-of-regard), receiver (element with defined actions), and listener (body).
					  document.body.addEventListener("dismissrequest", handleDismiss);
					  document.body.addEventListener("panrequest", handlePan);
					  document.body.addEventListener("deleterequest", handleDelete);
					  document.body.addEventListener("zoomrequest", handleZoom);
					</script>
				

In the previous example, the "deleterequest" event may be fired any time the user's point-of-regard was inside the document, presumably when the user triggered their platform's physical event to initiate a deletion, such as pressing the DELETE key. However, the "dismissrequest" would only be fired when the user's point-of-regard was inside the dialog. Likewise, the "panrequest" and "zoomrequest" would only be fired when the user's point-of-regard was inside the map view.

UI Request Events

There is purposefully no request event for activating the default action. Authors are encouraged to use a standard click event for default actions. Update: Eitan (Mozilla) requested ACTION-53: activate request event to augment default action trigger when click handlers are inappropriate.

Event fires on point-of-regard (document.activeElement, clicked element, or AT equivalent) if applicable, or otherwise document.body.

Event order: These events should be asynchronous, but when used in conjunction with keyboard events, we need to define where each IndieUI event fires in the chain of keydown, keyup, and keypress. Probably also need an identifier to associate each event with other related physical events: e.g. This dismissrequest event is associated with the keyboard events keydown, keyup, and keypress of the ESC key.

Interface UIRequestEvent

Separate interface from UIEvent because the @uiactions attribute will 1) affect when and where these events are fired, and 2) adds the distinction of an event receiver element (element declaring the uiactions attribute) in addition to the "target" element where the event initiates and the "listener" element where the event is registered for and handled.

The receiver attribute of each instance of the UIRequestEvent interface MUST return an EventTarget matching the DOMElement where the corresponding event's action is declared via the uiactions attribute.

readonly attribute EventTarget receiver
In addition to the event target, each UI Request Event has a receiver element, which is declared via the uiactions content attribute on an ancestor node of the event target.

Determining the Event Receiver

The event receiver is determined using the following steps:

  1. For each event name literal ("dismissrequest"), determine the corresponding uiactions token ("dismiss").
  2. Starting with the event's target element, determine if the element's actions list contains the corresponding action for the event (el.uiactions.contains("dismiss")). If the current element's action list contains the corresponding uiactions token, the event target is also the event receiver.
  3. If the current element's action list does not contain the corresponding uiactions token, move up to the parent element and try again. Continue until reaching the root element. The closest ancestor to match the corresponding action token is the event receiver.
  4. If the event receiver is still undetermined upon reaching the root element, stop. There is no valid event receiver and the user agent MUST NOT initiate the event.

May also need a way to associate IndieUI events with their physical event counterparts.

[Example]
partial interface UIEvent {
  readonly attribute EventID id; // UID of current event
  readonly attribute EventList relatedEvents; // List of related events, with ID and potentially type of each event. 
  // This "dismissrequest" event is associated with the previous "keydown" and "keyup" events.
}

UIRequestEventInit

boolean bubbles = true
boolean cancelable = true
WindowProxy? view = null
long detail = 0
EventTarget receiver = null

UIRequestEvent Types

The different types of UIRequestEvents that can occur are:

Undo Request (undorequest)

Indicates the user desires to "undo" the previous action.

May be superseded by the UndoManager interface.

  • Bubbles: Yes
  • Cancelable: Yes

Users, wanting to "undo" a discrete action in a web application, can indicate their intent a number of ways, including pressing Control+Z on Windows or Linux, Command+Z on Mac OS X, and even by shaking some accelerometer- or gyroscope-enabled mobile devices.

Redo Request (redorequest)

Indicates the user desires to "redo" the previously "undone" action.

May be superseded by the UndoManager interface.

  • Bubbles: Yes
  • Cancelable: Yes

Users, wanting to "redo" a discrete action in a web application, can indicate their intent a number of ways, including pressing Control+Shift+Z on Windows or Linux, Command+Shift+Z on Mac OS X.

Expand Request (expandrequest)

Indicates the user desires to to reveal information in a collapsed section (e.g. a disclosure widget) or branch node in a hierarchy (e.g., a tree view).

  • Bubbles: Yes
  • Cancelable: Yes
Collapse Request (collapserequest)

Indicates the user desires to hide or collapse information in an expanded section (e.g. a disclosure widget) or branch node in a hierarchy (e.g., a tree view).

  • Bubbles: Yes
  • Cancelable: Yes
Dismiss Request (dismissrequest)

Indicates the user desires "dismiss" the current view (e.g. canceling a dialog, or closing a popup menu).

  • Bubbles: Yes
  • Cancelable: Yes

Users, wanting to "escape from" or "dismiss" a web application state (for example, closing a modal dialog), can indicate their intent a number of ways, most commonly by pressing Escape on keyboard-controlled operating systems. Web authors who have registered for this event should process the event to determine whether to cancel the event. If the "dismiss" action is understood in the context of the web application, web authors should perform the appropriate action (such as closing the dialog), and cancel the event using the event object's preventDefault() method.

Delete Request (deleterequest)

Indicates the user wants to initiate a "delete" action on the marked element or current view.

  • Bubbles: Yes
  • Cancelable: Yes
Pause Media Playback Request (mediapauserequest)

Initiated when the user agent sends a request to the web application to pause media playback.

  • Bubbles: Yes
  • Cancelable: Yes
Start Media Playback Request (mediastartrequest)

Initiated when the user agent sends a request to the web application to start media playback.

  • Bubbles: Yes
  • Cancelable: Yes
Stop Media Playback Request (mediastoprequest)

Initiated when the user agent sends a request to the web application to stop media playback.

  • Bubbles: Yes
  • Cancelable: Yes
Toggle Media Playback Request (mediatogglerequest)

Initiated when the user agent sends a request to the web application to toggle the play/pause state of media playback.

  • Bubbles: Yes
  • Cancelable: Yes
Previous Track Request (mediapreviousrequest)

Initiated when the user agent sends a request to the web application to skip media to the previous track boundary.

  • Bubbles: Yes
  • Cancelable: Yes
Next Track Request (medianextrequest)

Initiated when the user agent sends a request to the web application to skip media to the next track boundary.

  • Bubbles: Yes
  • Cancelable: Yes

There may be a need for continuous media request events to support fast-forward or rewind via press-and-hold, or double-click-and-hold, etc.

Interface UIFocusRequestEvent

Will probably need an ARIA 1.1 or 2.0 role for palette.

readonly attribute FocusRequestFocusType focusType

Enumeration FocusRequestFocusType

none
Not applicable. Event is not a linear or directional focus event.
navFirst
linear first
navPrevious
linear previous
navNext
linear next
navLast
linear last
navUp
directional "North"
navUpRight
directional "Northeast"
navRight
directional "East"
navDownRight
directional "Southeast"
navDown
directional "South"
navDownLeft
directional "Southwest"
navLeft
directional "West"
navUpLeft
directional "Northwest"

UIFocusRequestEventInit

boolean bubbles = true
boolean cancelable = true
WindowProxy? view = null
long detail = 0
EventTarget receiver = null
FocusRequestFocusType focusType = "NONE"
Type of linear or directional focus requested, as defined in the FocusRequestFocusType enumeration definition. Value remains "NONE" except when used for directionalfocusrequest or linearfocusrequest.

UIFocusRequestEvent Types

FIXME: explain these can cover focus changes when the element to focus is not yet loaded in the DOM or yet focusable (for example, in list or table views where the entire dataset is not displayed), or non-linear focus shortcuts or overrides when linear focus is not possible (for example, jumping directly from a contenteditable region to the editing toolbar, when Tab and Shift+Tab mean other things).

The types of UIFocusRequestEvents that can occur are:

Directional Focus Request (directionalfocusrequest)

Initiated when the user agent sends a "direction focus" request to the web application. Web authors SHOULD NOT use or register for directionalfocusrequest events when standard browser focus and blur events are sufficient. Using these events unnecessarily could result is reduced performance or an other negative user experience.

  • Bubbles: Yes
  • Cancelable: Yes
  • Context Info: focusType (one of directional focusType string)
Linear Focus Request (linearfocusrequest)

Initiated when the user agent sends a "linear focus" request to the web application. Web authors SHOULD NOT use or register for linearfocusrequest events when standard browser focus and blur events are sufficient. This event type is only necessary on specialized control types such as data grids where the logical next element may not be focusable or even in the DOM until requested. Using these events unnecessarily could result is reduced performance or an other negative user experience.

  • Bubbles: Yes
  • Cancelable: Yes
  • Context Info: focusType (one of linear focusType strings)
Palette Focus Request (palettefocusrequest)

Initiated when the user agent sends a "palette focus" request to the web application. Web app authors receiving this event SHOULD move focus to the first palette in the web application, or cycle focus between all available palettes. Note: palettes are sometimes referred to as non-modal dialogs or inspector windows.

  • Bubbles: Yes
  • Cancelable: Yes
Toolbar Focus Request (toolbarfocusrequest)

Initiated when the user agent sends a "toolbar focus" request to the web application. Web app authors receiving this event SHOULD move focus to the main toolbar in the web application, or cycle focus between all available toolbars.

  • Bubbles: Yes
  • Cancelable: Yes

Interface UIManipulationRequestEvent

readonly attribute double? originX
readonly attribute double? originY
readonly attribute double deltaX
readonly attribute double deltaY
readonly attribute double scaleFactor
readonly attribute double rotation

UIManipulationRequestEventInit

boolean bubbles = true
boolean cancelable = true
WindowProxy? view = null
long detail = 0
EventTarget receiver = null
double? originX = null
The cartesian X coordinate origin point (if one exists), measured in CSS pixels from the inside(?) left edge of element border box for the receiver element.
double? originY = null
The cartesian Y coordinate origin point (if one exists), measured in CSS pixels from the inside(?) top edge of element border box for the receiver element.
double deltaX = 0.0
The cartesian X coordinate delta from the event origin, measured in CSS pixels.
double deltaY = 0.0
The cartesian Y coordinate delta from the event origin, measured in CSS pixels.
double scaleFactor = 1.0
Scale factor, used in zoom manipulations, where 1.0 is the original scale factor. For example, a value of 2.0 or 3.0 indicates the element should enlarge to 2 or 3 times its original scale, respectively. A value of 0.5 indicates the element should decrease to one-half its original scale.
double rotation = 0.0
Rotation value, in degrees from 0. Positive values indicate a counter-clockwise rotation. Negative values indicate a clockwise rotation.

Discrete UIManipulationRequestEvent Types

Move and Pan request events are functionally identical, but are specified individually to aid in authoring clarity when using similar concepts like 1) moving an object on a layout canvas, and 2) panning a continuous view like a map.

The discrete types of UIManipulationRequestEvents that can occur are:

Move Request (moverequest)

Initiated when the user agent sends a move request to the web application with accompanying x/y delta values. This is used, for example, when moving an object to a new location on a layout canvas.

  • Bubbles: Yes
  • Cancelable: Yes
  • Context Info: deltaX, deltaY
Pan Request (panrequest)

Initiated when the user agent sends a pan request to the web application with accompanying x/y delta values. This is used, for example, when changing the center point while panning a map or another custom image viewer.

  • Bubbles: Yes
  • Cancelable: Yes
  • Context Info: deltaX, deltaY
Rotation Request (rotationrequest)

Initiated when the user agent sends a rotation request to the web application with accompanying origin x/y values and a rotation value in degrees.

  • Bubbles: Yes
  • Cancelable: Yes
  • Context Info: originX, originY, rotation

In the case where a User Agent lacks a clear or relevant point of origin, user agents could send null values for originX and originY, or they could send x/y coordinates representing the center point of the event.receiver element.

For example, many photo manipulation applications allow users to change orientation, or rotating a photograph 90 degrees, by pressing a key combination like Option+LeftArrow or Option+RightArrow. Since this represents a keyboard only event that is unrelated to the mouse pointer location, it would be appropriate to send null values. In many cases, web applications may not require the origin x/y coordinates for rotation events even if non-null values exist.

Zoom Request (zoomrequest)

Initiated when the user agent sends a zoom request to the web application with accompanying origin x/y values and the zoom scale factor. This may be used, for example, with a map view or custom layout view.

  • Bubbles: Yes
  • Cancelable: Yes
  • Context Info: originX, originY, scaleFactor

Web authors may use originX and originY in the way they deem most appropriate for the context of their application. In most cases, web applications receiving zoomrequest events will center the UI "zoom" on the originX/originY coordinates if they are provided. If origin coordinates are not provided, such as in the case of a keyboard-only zoom event, web authors will likely center the UI "zoom" in the middle of the receiving view.

There may be a need for a combined, continuous manipulation events (e.g. Pan+Zoom simultaneously) in addition to the discrete events listed above, but the following specification ideas are incomplete. For example, we're currently missing a feature to associate related events, and a description of what "canceling" implies.

Continuous UIManipulationRequestEvent Types

These continuous events may need an identifier per manipulation, for example, to associate a manipulationcancelrequest with the originating manipulationstartrequest that needs to be canceled.

The continuous types of UIManipulationRequestEvents that can occur are:

Manipulation Start Request (manipulationstartrequest)

TBD

  • Bubbles: Yes
  • Cancelable: Yes
  • Context Info: originX, originY, deltaX, deltaY, rotation, scaleFactor
Manipulation Change Request (manipulationchangerequest)

TBD

  • Bubbles: Yes
  • Cancelable: Yes
  • Context Info: originX, originY, deltaX, deltaY, rotation, scaleFactor
Manipulation End Request (manipulationendrequest)

TBD

  • Bubbles: Yes
  • Cancelable: Yes
  • Context Info: originX, originY, deltaX, deltaY, rotation, scaleFactor
Manipulation Cancel Request (manipulationcancelrequest)

TBD

  • Bubbles: Yes
  • Cancelable: Yes
  • Context Info: originX, originY, deltaX, deltaY, rotation, scaleFactor

Interface UIScrollRequestEvent

readonly attribute double? deltaX
readonly attribute double? deltaY
readonly attribute ScrollRequestScrollType scrollType

Enumeration ScrollRequestScrollType

deltas
Default value for scrollType indicating that scroll amount is provided as deltaX and deltaY in CSS pixels.
up
Equivalent to the default behavior of the UP key in most native scroll views.
right
Equivalent to the default behavior of the RIGHT key in most native scroll views.
down
Equivalent to the default behavior of the DOWN key in most native scroll views.
left
Equivalent to the default behavior of the LEFT key in most native scroll views.
pageUp
Equivalent to the default behavior of the PAGEUP key in most native scroll views.
pageRight
pageDown
Equivalent to the default behavior of the PAGEDOWN key in most native scroll views.
pageLeft
limitUp
Equivalent to the default behavior of the HOME key in most native scroll views.
limitRight
limitDown
Equivalent to the default behavior of the END key in most native scroll views.
limitLeft

UIScrollRequestEventInit

boolean bubbles = true
boolean cancelable = true
WindowProxy? view = null
long detail = 0
EventTarget receiver = null
double? originX = 0.0
The cartesian X coordinate origin point (if one exists), measured in CSS pixels from the inside(?) left edge of element border box for the receiver element.
double? originY = 0.0
The cartesian Y coordinate origin point (if one exists), measured in CSS pixels from the inside(?) top edge of element border box for the receiver element.
double? deltaX = 0.0
The cartesian X coordinate delta from the event origin, measured in CSS pixels.
double? deltaY = 0.0
The cartesian Y coordinate delta from the event origin, measured in CSS pixels.
ScrollRequestScrollType scrollType = "deltas"

UIScrollRequestEvent Types

The discrete type of UIScrollRequestEvent that can occur is:

Scroll Request (scrollrequest)

Initiated when the user agent sends a scroll request to the web application with accompanying x/y delta values or one of the other defined scrollType values. Authors SHOULD only use this event and uiaction with custom scroll views that cannot be acheieved with native scroll views, because the hardware-accellerated scrolling of native views will always outperform these events.

Need an example here and clarifying text to indicate UAs "must" either send a non-default scrollType, or non-default deltas, but not both.

  • Bubbles: Yes
  • Cancelable: Yes
  • Context Info: scrollType, deltaX, and deltaY

Continuous UIScrollRequestEvent Types

These continuous events may need an identifier per scroll, for example, to associate a scrollcancelrequest with the originating scrollstartrequest that needs to be canceled.

The continuous types of UIScrollRequestEvents that can occur are:

Scroll Start Request (scrollstartrequest)

TBD

  • Bubbles: Yes
  • Cancelable: Yes
  • Context Info: originX, originY, deltaX, deltaY
Scroll Move Request (scrollmoverequest)

TBD

  • Bubbles: Yes
  • Cancelable: Yes
  • Context Info: originX, originY, deltaX, deltaY
Scroll End Request (scrollendrequest)

TBD

  • Bubbles: Yes
  • Cancelable: Yes
  • Context Info: originX, originY, deltaX, deltaY
Scroll Cancel Request (scrollcancelrequest)

TBD

  • Bubbles: Yes
  • Cancelable: Yes
  • Context Info: originX, originY, deltaX, deltaY

Interface UIValueChangeRequestEvent

readonly attribute ValueChangeRequestChangeType changeType

Enumeration ValueChangeRequestChangeType

unknown
increment
Equivalent to the default behavior of the UP key on most native sliders.
incrementSmall
Equivalent to the behavior of ALT+UP or OPTION+UP on some native controls, indicating a finely tuned adjustment (e.g. +0.1% as opposed to +1%).
incrementLarge
Equivalent to the default behavior of PAGEUP or SHIFT+UP on many native sliders.
incrementMaximum
Equivalent to the default behavior of the END key on most native sliders.
decrement
Equivalent to the default behavior of the DOWN key on most native sliders.
decrementSmall
Equivalent to the behavior of ALT+DOWN or OPTION+DOWN on some native controls, indicating a finely tuned adjustment (e.g. -0.1% as opposed to -1%).
decrementLarge
Equivalent to the default behavior of PAGEDOWN or SHIFT+DOWN on many native sliders.
decrementMinimum
Equivalent to the default behavior of the HOME key on most native sliders.

UIValueChangeRequestEventInit

boolean bubbles = true
boolean cancelable = true
WindowProxy? view = null
long detail = 0
EventTarget receiver = null
ValueChangeRequestChangeType changeType = "UNKNOWN"

UIValueChangeRequestEvent Types

The single type of UIValueChangeRequestEvent that can occur is:

Value Change Request (valuechangerequest)

Initiated when the user agent sends a value change request to the web application. Used on custom range controls like sliders, carousels, etc.

Web authors MUST code applications to accept all values of the changeType attribute. For example, if there is no special behavior for INCREMENT_SMALL or INCREMENT_LARGE, web applications would behave as if they had received a basic INCREMENT change type.

  • Bubbles: Yes
  • Cancelable: Yes
  • Context Info: changeType

Users, wanting to change the value of a custom range widget (e.g. sliders or carousels) in a web application, can indicate their intent a number of ways, including pressing various keys (Up, Down, Left, Right, PageUp, PageDown, Home, End) on most keyboard-controlled interfaces. User agents understanding this intent should initiate a valuechangerequest event. Web authors who have registered for this event, should process the event to determine whether to cancel the event. If the value change action is understood in the context of the web application, web authors should change the value of the associated widget by an amount determined via the changeType argument, and cancel the event using the event object's preventDefault() method.

Feature Detection

Authors wishing to conditionally assign request event handlers based on whether the user agent supports these events can use standard objection detection for each event handler or property.

Conditionally Assigning a UI Request Event

The following example conditionally assigns a "dismissrequest" event based on whether the user agent has support for the feature.

						if (typeof document.body.ondismissrequest !== "undefined") {
						  // Okay to use "dismissrequest" event.
						  document.body.addEventListener("dismissrequest", dismissHandler);
						} else {
						  // Otherwise catch the ESC key or another platform-specific equivalent event.
						  document.body.addEventListener("keyup", keyHandler);
						}
					

Note: need to double-check that the above code sample is really the best approach.

Events List (alphabetical)

Substantive, normative changes since the last public working draft