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<h1>UI Events Algorithms</h1>
<pre class="metadata">
Shortname: uievents-algo
Level:
Group:
Status: DREAM
Editor: Gary Kacmarcik, Google, [email protected]
Abstract:
This document attempts to describe, in an algorithmic manner, how UIEvents
should be handled by User Agents. Because this functionality has been shipping
in UAs for many years, the primary goal is to document the existing behaviors
and identify areas where implementations disagree. The intent is to fold this
information into the main UIEvents spec (and other specs) once there is
consensus that this process described here is adequate.
</pre>
<pre class="anchors">
urlPrefix: https://www.w3.org/TR/uievents/#; type: dfn; spec: uievents;
text: compositionend
text: compositionstart
urlPrefix: https://html.spec.whatwg.org/#; type: dfn; spec: html;
text: click focusable
text: focusable area
text: focusing steps
url: https://www.w3.org/TR/uievents-key/#keys-modifier; type: dfn; spec: uievents-key;
text: modifier key
url: https://www.w3.org/TR/CSS2/visuren.html#viewport; type: dfn; spec: css2;
text: viewport
url: https://www.w3.org/TR/cssom-view-1/#dom-document-elementfrompoint; type: dfn; spec: cssom-view;
text: elementFromPoint
text: elementsFromPoint
url: https://dom.spec.whatwg.org/#concept-event-dispatch; type: dfn; spec: html;
text: dispatch
</pre>
<pre class="link-defaults">
spec:cssom-view; type:attribute; for:MouseEvent; text:x
spec:cssom-view; type:attribute; for:MouseEvent; text:y
spec:dom; type:attribute; for:Event; text:bubbles
spec:dom; type:attribute; for:Event; text:cancelable
spec:dom; type:attribute; for:Event; text:composed
spec:dom; type:attribute; for:Event; text:target
spec:dom; type:attribute; for:Event; text:type
spec:dom; type:const; text:NONE
spec:ui-events; type:attribute; for:InputEvent; text:inputType
spec:ui-events; type:attribute; for:KeyboardEvent; text:code
spec:ui-events; type:attribute; for:MouseEvent; text:button
spec:ui-events; type:attribute; for:MouseEvent; text:buttons
spec:ui-events; type:attribute; for:MouseEvent; text:clientX
spec:ui-events; type:attribute; for:MouseEvent; text:clientY
spec:ui-events; type:attribute; for:MouseEvent; text:screenX
spec:ui-events; type:attribute; for:MouseEvent; text:screenY
spec:ui-events; type:attribute; for:UIEvent; text:detail
spec:ui-events; type:attribute; for:UIEvent; text:view
spec:ui-events; type:attribute; for:UIEvent; text:which
</pre>
<section>
<h2 id="intro">Why?</h2>
The description of events in the current UIEvents spec is woefully underspecified.
This has led to different User Agents (UAs) implementing the same feature with
different behaviors.
The intent with this document is to:
* Describe the current behaviors that are shared by existing UAs
* Identify behaviors where they differ
* Initiate discussions to resolve the differences
Part of this process will necessarily require that we describe processes that
rightfully belong in other specifications (e.g., Pointer Events or Input Events).
The intent is to eventually move those portions into their appropriate home,
but they are kept here while drafting this document to make it easier to discuss.
</section>
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<section>
<h2 id="native-os">Native OS Requirements</h2>
The following is the set of assumptions that this specification makes about the
underlying native operating system. It is expected that the native OS will
provide these basic services for the UA.
In the event that the native OS does not provide these services, then the
UA will need to implement them.
<h3 id="req-mouse">MouseEvent Requirements</h3>
The native OS platform will provide:
* An event when the mouse is moved
* An event when a mouse button is pressed
* An event when a mouse button is released
* A way to identify when a mouse button press should be interpreted as a "click"
* For example, as a flag or as a separate event
* If a separate "click" event is fired, then the native OS will fire it
immediately after the corresponding "mouse up" event, with no
intervening mouse-related events
* A way to identify when a mouse click is a "double click"
For these events, the OS will be able to provide the following info:
* The x,y mouse coordinates relative to the native OS desktop
* The x,y mouse coordinates relative to the UA's window viewport
* Which keyboard modifiers are currently being held
<h3 id="req-touch">PointerEvent Requirements</h3>
TODO: Specify native requirements here.
<h3 id="req-keyboard">KeyboardEvent Requirements</h3>
The native OS platform will provide:
* An event when a key is pressed
Note: On Windows: WM_KEYDOWN, WM_SYSKEYDOWN
Note: On macOS: NSKeyDown, NSFlagsChanged (for modifiers without other keys)
* An event when a key is released
Note: On Windows: WM_KEYUP, WM_SYSKEYUP
Note: On macOS: NSKeyUp, NSFlagsChanged (for modifiers without other keys)
* An event when a character should be generated as a result of a keypress
* This may be a separate event, or it may be combined with the keydown event
* If a separate event, then there are no intervening key events between keydown and char
Note: On Windows: WM_CHAR, WM_SYSCHAR
Note: On macOS: Combined with keydown
* An event when text should be inserted
* These are commonly used for alternate input devices like chordal keyboards or speech input
* This may be the same event as for when a key is pressed
Note: On Windows: WM_CHAR (without associated keydown/keyup)
Note: On macOS: NSTextInputClient with insertText
* A way to identify key events that are "repeat"s from the key being held down
* The platform will maintain a key repeat threshold
* A way to identify the modifier keys that are held in combination with a key press
* Either via flags in the messages, or via a separate call
Note: On Windows: included with WM_ messages
Note: On macOS: included with NSKey messages and NSFlagChanged
Note: On Linux (GTK): not provided with messages. need to request separately
<h3 id="req-ime">IME Requirements</h3>
Issue: IMEs differ wildly on different platforms, and often have different capabilities
(such as whether or not they can be "canceled") even on the same platform.
What is the common set of requirements that we can rely on?
Issue: For example, on Windows, Win+'.' opens an emoji window that will generate
composition events. But there is not indication from the OS that composition
is about to take place. A similar problem exists with "shape writing" using the
virtual keyboard.
<h3 id="native-entry-points">Native Entry Points</h3>
<h4 id="native-mouse">Mouse</h4>
* <a>handle native mouse down</a>
* <a>handle native mouse up</a>
* <a>handle native mouse click</a>
* <a>handle native mouse double click</a>
* <a>handle native mouse move</a>
<h4 id="native-touch">Touch</h4>
TODO: Include native touch events and resolve with native mouse events. How do these two
event types interact on the common platforms? When are mouse events generated from
touch events?
<h4 id="native-keyboard">Keyboard</h4>
* <a>handle native key down</a>
* <a>handle native key press</a>
* <a>handle native key up</a>
<h4 id="native-clipboard">Clipboard</h4>
* <a>handle native cut</a>
* <a>handle native copy</a>
* <a>handle native paste</a>
</section>
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<section>
<h2 id="event">Event</h2>
Issue: Move to/merge with [[DOM]] spec {{Event}} interface.
<h3 id="event-interface">Event Interface</h3>
A {{Event}} has the following additional internal state:
<dl dfn-for="UIEvent">
<li><dfn>due to user interaction flag</dfn>
Issue: This is a proposal.
See <a href="https://github.com/w3c/uievents/issues/270">uievents/270</a>
</li>
</dl>
<div class="algorithm" data-algorithm="initialize-an-event">
<h3 id="initialize an event"><dfn>initialize an Event</dfn></h3>
: Input
:: |event|, the {{Event}} to initialize
:: |eventType|, a DOMString containing the event type
:: |eventTarget|, the {{EventTarget}} of the event
: Output
:: None
For reference, see
<a href="https://dom.spec.whatwg.org/#concept-event-initialize">initialize an event</a>,
<a href="https://dom.spec.whatwg.org/#stop-propagation-flag">list of event flags</a>.
1. Initialize the following public attributes
1. Set |event|.{{type}} = |eventType|
1. Set |event|.{{target}} = |eventTarget|
1. Set |event|.{{currentTarget}} = null (This will be set appropriately during dispatch)
1. Set |event|.{{eventPhase}} = {{NONE}} (This will be set appropriately during dispatch)
1. Set |event|.{{bubbles}} = true
1. Set |event|.{{cancelable}} = true
1. Set |event|.{{defaultPrevented}} = false
1. Set |event|.{{composed}} = false // See COMPAT note for mouseenter and mouseleave
1. Set |event|.{{isTrusted}} = false
1. Set |event|.{{timeStamp}} = Number of milliseconds relative to the time origin
1. Initialize the following historical attributes
1. Set |event|.srcElement = |eventTarget|
1. Set |event|.cancelBubble = alias for stopPropagation
1. Set |event|.returnValue = alias for !canceled_flag
1. Initialize the following internal state
1. Unset |event|'s <a>stop propagation flag</a>
1. Unset |event|'s <a>stop immediate propagation flag</a>
1. Unset |event|'s <a>canceled flag</a>
1. Unset |event|'s <a>in passive listener flag</a>
1. Unset |event|'s <a>composed flag</a>
1. Unset |event|'s <a>initialized flag</a>
1. Unset |event|'s <a>dispatch flag</a>
1. Initialize the following proposed internal state
1. Unset |event|'s <a>due to user interaction flag</a>
</div><!-- algorithm -->
</section>
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<section>
<h2 id="ui event">UI Event</h2>
<h3 id="uievent-interface">UIEvent Interface</h3>
A {{UIEvent}} has the following:
<dl dfn-for="UIEvent">
<li><dfn attribute>view</dfn></li>
<li><dfn attribute>detail</dfn></li>
</dl>
Along with the following historical attribute:
<dl dfn-for="KeyboardEvent">
<li><dfn attribute>which</dfn></li>
</dl>
Issue: Add definition for UIEventInit
<div class="algorithm" data-algorithm="initialize-a-uievent">
<h3 id="initialize a uievent"><dfn>initialize a UIEvent</dfn></h3>
: Input
:: |event|, the {{UIEvent}} to initialize
:: |eventType|, a DOMString containing the event type
:: |eventTarget|, the {{EventTarget}} of the event
: Output
:: None
1. <a>Initialize an Event</a> with |event|, |eventType| and |eventTarget|
1. Initialize the following public attributes
1. Set |event|.{{view}} = the |eventTarget|'s <a>node document</a>'s {{Window}} object
1. Set |event|.{{detail}} = 0
1. Initialize the following historical attributes
1. Set |event|.{{which}} = 0 (used by both {{MouseEvent}} and {{KeyboardEvent}})
1. If this event is the result of user interaction, then
1. Set |event|'s <a>due to user interaction flag</a>
Note: See <a href="https://github.com/w3c/uievents/issues/270">uievents/270</a>
1. Set |event|.{{isTrusted}} = false
</div><!-- algorithm -->
Issue: Event firing for load, unload, abort, error, select. Should those be covered here
or are they handled elsewhere already?
</section>
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<section>
<h2 id="focus event">Focus Event</h2>
Issue: TODO
</section>
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<section>
<h2 id="mouse event">Mouse Event</h2>
<h3 id="mouseevent-interface">MouseEvent Interface</h3>
A {{MouseEvent}} has the following:
<dl dfn-for="MouseEvent">
<li><dfn attribute>screenX</dfn></li>
<li><dfn attribute>screenY</dfn></li>
<li><dfn attribute>clientX</dfn></li>
<li><dfn attribute>clientY</dfn></li>
<li><dfn attribute>ctrlKey</dfn></li>
<li><dfn attribute>shiftKey</dfn></li>
<li><dfn attribute>altKey</dfn></li>
<li><dfn attribute>metaKey</dfn></li>
<li><dfn attribute>button</dfn></li>
<li><dfn attribute>buttons</dfn></li>
<li><dfn attribute>relatedTarget</dfn></li>
<li>getModifierState(keyArg)</li>
</dl>
<h3 id="mouseevent-global-state">Global State for MouseEvent</h3>
<h4 id="mouseevent-global-ua">User Agent-Level State</h4>
The UA must maintain the following values that are shared for the entire
User Agent.
A <dfn>mouse button bitmask</dfn> that tracks the current state of the
mouse buttons.
<h4 id="mouseevent-global-window">Window-Level State</h4>
The UA must maintain the following values that are shared for the Window.
A <dfn>last mouse element</dfn> value (initially undefined) that keeps track
of the last {{Element}} that we sent a MouseEvent to.
A <dfn>last mouse DOM path</dfn> value (initially empty) that contains a snapshot
of the ancestors {{Element}}s of the <a>last mouse element</a> when the most recent mouse
event was sent.
<div class="algorithm" data-algorithm="initialize-a-mouseevent">
<h3 id="initialize a mouseevent"><dfn>initialize a MouseEvent</dfn></h3>
: Input
:: |event|, the {{MouseEvent}} to initialize
:: |eventType|, a DOMString containing the event type
:: |eventTarget|, the {{EventTarget}} of the event
: Output
:: None
1. <a>Initialize a UIEvent</a> with |event|, |eventType| and |eventTarget|
2. Initialize the following public attributes
1. Set |event|.{{screenX}} = the x-coordinate of the position where the event occurred
relative to the origin of the desktop
1. Set |event|.{{screenY}} = the y-coordinate of the position where the event occurred
relative to the origin of the desktop
1. Set |event|.{{clientX}} = the x-coordinate of the position where the event occurred
relative to the origin of the viewport
1. Set |event|.{{clientY}} = the y-coordinate of the position where the event occurred
relative to the origin of the <a>viewport</a>
1. <a>Set event modifiers</a> with |event|
1. Set |event|.{{button}} = 0
1. Set |event|.{{buttons}} = <a>mouse button bitmask</a>
1. <a>Initialize PointerLock attributes for MouseEvent</a> with |event|
1. <a>Initialize CSSOM attributes for MouseEvent</a> with |event|
</div><!-- algorithm -->
<div class="algorithm" data-algorithm="create-a-mouseevent">
<h3 id="create a mouseevent"><dfn>create a MouseEvent</dfn></h3>
: Input
:: |eventType|, a DOMString containing the event type
:: |eventTarget|, the {{EventTarget}} of the event
: Output
:: None
1. Let |event| = the result of
<a href="https://dom.spec.whatwg.org/#concept-event-create">creating a new event</a> using {{MouseEvent}}
1. <a>Initialize a MouseEvent</a> with |event|, |eventType| and |eventTarget|
1. Return |event|
</div><!-- algorithm -->
<div class="algorithm" data-algorithm="calculate-mouseevent-button-attribute">
<h3 id="calculate mouseevent button attribute"><dfn>calculate MouseEvent button attribute</dfn></h3>
: Input
:: |mbutton|, an ID that identifies a mouse button
: Output
:: A button ID suitable for storing in the {{MouseEvent}}'s {{button}} attribute
1. If |mbutton| is the primary mouse button, then return 0
1. If |mbutton| is the auxiliary (middle) mouse button, then return 1
1. If |mbutton| is the secondary mouse button, then return 2
1. If |mbutton| is the X1 (back) button, then return 3
1. If |mbutton| is the X2 (forward) button, then return 4
</div><!-- algorithm -->
<div class="algorithm" data-algorithm="set-mouseevent-attributes-from-native">
<h3 id="set mouseevent attributes from native"><dfn>set MouseEvent attributes from native</dfn></h3>
: Input
:: |event|, the {{MouseEvent}} to initialize
:: |native|, the native mouse event
: Output
:: None
Issue: TODO
1. If |event|.{{type}} is one of [ mousedown, mouseup ], then
1. Let |mbutton| be an ID from |native| that identifies which mouse button was pressed
1. Set |event|.{{button}} = <a>calculate MouseEvent button attribute</a> with |mbutton|
</div><!-- algorithm -->
<div class="algorithm" data-algorithm="handle-native-mouse-down">
<h3 id="handle native mouse down"><dfn>handle native mouse down</dfn></h3>
: Input
:: |native|, the native mousedown
: Output
:: None
1. Let |mbutton| be an ID from |native| that identifies which mouse button was pressed
1. Update the <a>mouse button bitmask</a> as follows:
1. If |mbutton| is the primary mouse button, then set the 0x01 bit
1. If |mbutton| is the secondary mouse button, then set the 0x02 bit
1. If |mbutton| is the auxiliary (middle) mouse button, then set the 0x04 bit
Issue: Other buttons can be added starting with 0x08
1. Let |target| = <a>hit test</a> with viewport-relative coordinates from |native|
1. Let |event| = <a>create a MouseEvent</a> with "mousedown", |target|
1. <a>Set MouseEvent attributes from native</a> with |native|
1. <a>Maybe send pointerdown event</a> with |event|
1. Let |result| = <a>dispatch</a> |event| at |target|
1. If |result| is true and |target| is a <a>focusable area</a> that is <a>click focusable</a>, then
1. Run the <a>focusing steps</a> at |target|
1. if |mbutton| is the secondary mouse button, then
1. <a>Maybe show context menu</a> with |native|, |target|
</div><!-- algorithm -->
<div class="algorithm" data-algorithm="handle-native-mouse-up">
<h3 id="handle native mouse up"><dfn>handle native mouse up</dfn></h3>
: Input
:: |native|, the native mouseup
: Output
:: None
Note: Other mouse events can occur between the mousedown and mouseup.
1. Let |mbutton| be an ID from |native| that identifies which mouse button was pressed
1. Update the <a>mouse button bitmask</a> as follows:
1. If |mbutton| is the primary mouse button, then clear the 0x01 bit
1. If |mbutton| is the secondary mouse button, then clear the 0x02 bit
1. If |mbutton| is the auxiliary (middle) mouse button, then clear the 0x04 bit
1. Let |target| = <a>hit test</a> with viewport-relative coordinates from |native|
1. Let |event| = <a>create a MouseEvent</a> with "mouseup", |target|
1. <a>Set MouseEvent attributes from native</a> with |native|
1. <a>Maybe send pointerup event</a> with |event|
1. <a>dispatch</a> |event| at |target|
</div><!-- algorithm -->
<div class="algorithm" data-algorithm="handle-native-mouse-click">
<h3 id="handle native mouse click"><dfn>handle native mouse click</dfn></h3>
: Input
:: |native|, the native mouse click
: Output
:: None
Note: The platform should call this immediately after <a>handle native mouse up</a> for
mouseups that generate clicks.
1. Let |target| = <a>hit test</a> with viewport-relative coordinates from |native|
1. <a>Send click event</a> with |native| and |target|.
</div><!-- algorithm -->
<div class="algorithm" data-algorithm="send-click-event">
<h3 id="send click event"><dfn>send click event</dfn></h3>
: Input
:: |native|, the native mousedown
:: |target|, the {{EventTarget}} of the event
: Output
:: None
1. Let |mbutton| = 1 (primary mouse button by default)
1. If |native| is valid, then
1. Let |mbutton| be an ID from |native| that identifies which mouse button was pressed
1. Let |eventType| = "auxclick"
1. If |mbutton| is the primary mouse button, then
1. Set |eventType| = "click"
1. Let |event| = <a>create a PointerEvent</a> with |eventType| and |target|
1. If |native| is valid, then
1. <a>Set MouseEvent attributes from native</a> with |event|, |native|
1. If |event|.{{screenX}} is not an integer value, then round it.
1. If |event|.{{screenY}} is not an integer value, then round it.
1. <a>dispatch</a> |event| at |target|
Note: See <a href="https://github.com/w3c/pointerevents/issues/100">pointerevents/100</a>
for info about browsers using PointerEvents and rounded coordinates.
Note: Any "default action" is handled during dispatch by triggering the
<a href="https://dom.spec.whatwg.org/#eventtarget-activation-behavior">activation behavior</a>
algorithm for the target. So there is no need for handle that here.
However, need to verify that the existing spec handles disabled/css-pointer-events/inert/...
Note: To handle `HTMLelement.click()`, call this algorithm with |native| = null and
|target| = `HTMLelement`.
Note: To handle keyboard-initiated clicks, call this algorithm with |native| = null and
|target| = currently focused element.
</div><!-- algorithm -->
<div class="algorithm" data-algorithm="handle-native-mouse-double-click">
<h3 id="handle native mouse double click"><dfn>handle native mouse double click</dfn></h3>
: Input
:: |native|, the native mouse double click
: Output
:: None
Note: This should be called immediately after handle native mouse click for
mouse clicks that generate double clicks.
1. Let |mbutton| be an ID from |native| that identifies which mouse button was pressed
1. If |mbutton| is not the primary mouse button, then return
1. Let |target| = <a>hit test</a> with viewport-relative coordinates from |native|
1. Let |event| = <a>create a PointerEvent</a> with "dblclick" and |target|
1. <a>Set MouseEvent attributes from native</a> with |event|, |native|
1. If |event|.{{screenX}} is not an integer value, then round it.
1. If |event|.{{screenY}} is not an integer value, then round it.
1. <a>dispatch</a> |event| at |target|
</div><!-- algorithm -->
<div class="algorithm" data-algorithm="handle-native-mouse-move">
<h3 id="handle native mouse move"><dfn>handle native mouse move</dfn></h3>
: Input
:: |native|, the native mouse move
: Output
:: None
Issue: This algorithm makes assumptions about the dispatch of PointerEvents because they
are not currently specified explicitly. Once
<a href="https://github.com/w3c/pointerevents/issues/285">pointerevents/285</a> is resolved
this may need to be updated.
1. Let |target| = <a>hit test</a> with viewport-relative coordinates from |native|
1. Let |targetDomPath| = <a>calculate DOM path</a>
1. Generate events for leaving the current element:
1. If <a>last mouse element</a> is defined and not equal to |target|, then
1. Let |mouseout| = <a>create a MouseEvent</a> with "mouseout" and <a>last mouse element</a>
Issue: TODO: Set |mouseout| attributes from |native|. +CSSOM attributes
1. <a>Maybe send pointerout event</a> with |mouseout|
1. <a>Dispatch</a> |mouseout| at |target|
Issue: Verify behavior when canceled (appears to have no effect).
1. Let |leaveElements| be a copy of <a>last mouse DOM path</a> with all
elements common to |targetDomPath| removed.
1. For each |element| in |leaveElements|, do
Issue: Handle case where |element| has been deleted.
Also case where it has been moved: Should the DOM mutation have triggered
a mouseleave event? Should we sent it now? Should it be dropped?
Need to verify what current browsers do.
1. Let |mouseleave| = <a>create a MouseEvent</a> with "mouseleave" and |element|
1. Set |mouseleave|.{{bubbles}} = false
1. Set |mouseleave|.{{cancelable}} = false
1. Set |mouseleave|.{{composed}} = false
Issue: Compat: Value of event.composed. Spec says false.
Chrome/Linux = true
Firefox/Linux = false
1. <a>Maybe send pointerleave event</a> with |mouseleave|
1. Let |result| = <a>dispatch</a> |mouseleave| at |element|
1. Generate events for entering the new element:
1. If |target| is not <a>last mouse element</a>, then
1. Let |mouseover| = <a>create a MouseEvent</a> with "mouseover" and |target|
Issue: TODO: Set |mouseout| attributes from |native|. +CSSOM attributes
1. <a>Maybe send pointerover event</a> with |mouseover|
1. <a>Dispatch</a> |mouseout| at |target|
Issue: Verify behavior when canceled (appears to have no effect).
1. Let |enterElements| be a copy of |targetDomPath| with all
elements common to <a>last mouse DOM path</a> removed.
1. For each |element| in |enterElements|, do
Issue: Handle case where |element| has been deleted or moved.
1. Let |mouseenter| = <a>create a MouseEvent</a> with "mouseenter" and |element|
1. Set |mouseenter|.{{bubbles}} = false
1. Set |mouseenter|.{{cancelable}} = false
1. Set |mouseenter|.{{composed}} = false
Issue: Compat: Value of event.composed. Spec says false.
Chrome/Linux = true
Firefox/Linux = false
1. <a>Maybe send pointerenter event</a> with |mouseenter|
Issue: Compat for shadow DOM elements
Chrome/Linux fires this event at the element and the shadow root
1. Let |result| = <a>dispatch</a> |mouseenter| at |element|
1. Set <a>last mouse element</a> to |target|
1. Set <a>last mouse DOM path</a> to |targetDomPath|
1. Let |mousemove| = <a>create a MouseEvent</a> with "mousemove" and |element|
1. <a>Set PointerLock attributes for mousemove</a>
1. <a>Maybe send pointermove event</a> with |mousemove|
1. <a>Dispatch</a> |mousemove| at |element|
</div><!-- algorithm -->
<div class="algorithm" data-algorithm="maybe-show-context-menu">
<h3 id="maybe show context menu"><dfn>maybe show context menu</dfn></h3>
: Input
:: |native|, the native mousedown or pointer event
:: |target|, the {{EventTarget}} of the event
: Output
:: None
1. Let |menuevent| = <a>create a PointerEvent</a> with "contextmenu", |target|
1. If |native| is valid, then
1. <a>Set MouseEvent attributes from native</a> with |native|
1. Let |result| = <a>dispatch</a> |menuevent| at |target|
1. If |result| is true, then show the UA context menu
Note: To handle a context menu triggered by the keyboard, call this algorithm with
|native| = null and |target| = currently focused element.
</section>
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<section>
<h2 id="wheel event">Wheel Event</h2>
Issue: TODO
</section>
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<section>
<h2 id="input event">Input Event</h2>
<div class="algorithm" data-algorithm="initialize-an-inputevent">
<h3 id="initialize an Inputevent"><dfn>initialize an InputEvent</dfn></h3>
: Input
:: |e|, the {{Event}} to initialize
:: |eventType|, a DOMString containing the event type
:: |eventTarget|, the {{EventTarget}} of the event
: Output
:: None
1. <a>Initialize a UIEvent</a> with |e|, |eventType| and |eventTarget|
1. Initialize the following public attributes
1. Set event.data = null
1. Set event.isComposing = false
1. Set event.inputType = ""
1. Set event.composed = true
Note: Setting composed to true matches current UA behavior, but it makes more sense
for this to be false.
See <a href="https://github.com/whatwg/html/issues/5453">whatwg/html/5453</a>
for discussion.
1. Initialize the additional editing attributes from [[Input Events]]
Issue: Move the following into InputEvents spec
(<a href="https://www.w3.org/TR/input-events-1/">level 1</a>
or
<a href="https://www.w3.org/TR/input-events-2/">level 2</a>)
since that's where these attributes are defined.
1. Set |e|.dataTransfer = false
1. Set |e|.targetRanges = []
</div><!-- algorithm -->
<div class="algorithm" data-algorithm="create-an-inputevent">
<h3 id="create an inputevent"><dfn>create an InputEvent</dfn></h3>
: Input
:: |eventType|, a DOMString containing the event type
:: |eventTarget|, the {{EventTarget}} of the event
: Output
:: None
1. Let |e| = the result of
<a href="https://dom.spec.whatwg.org/#concept-event-create">creating a new event</a> using {{InputEvent}}
1. <a>Initialize an InputEvent</a> with |e|, |eventType| and |eventTarget|
1. Return |e|
</div><!-- algorithm -->
<div class="algorithm" data-algorithm="fire-key-input-events">
<h3 id="fire key input events"><dfn>fire key input events</dfn></h3>
: Input
:: |key|, a DOMString containing the string corresponding to the key
:: |target|, the {{EventTarget}} of the event
: Output
:: None
1. If <a>suppress key input events flag</a> is set, then
1. Exit (since the keydown was canceled)
Issue: Handle historical keypress event here
1. Let |inputType| = null
1. Let |data| = null
Issue: How much of this can be moved into the [[Input Events]] spec?
Issue: List more keys here
1. If |key| is "Backspace", then |inputType| = "deleteContentBackward"
1. If |key| is "Delete", then |inputType| = "deleteContentForward"
1. Otherwise,
1. |inputType| = "insertText"
1. |data| = |key|
1. If |inputType| is not null, then
Note: Need to verify Firefox behavior.
Can be enabled by changing the "dom.input_events.beforeinput_enabled" pref in "about:config"
1. Let |result| = <a>fire an InputEvent</a> with "beforeinput", |inputType| and |data|
1. If |result| is true
Note: Perform DOM update here. Insert key into |target| element
Note: Compat:
For insertFromPaste, Chrome has data = null, Firefox has data = same as beforeinput.
1. <a>Fire an InputEvent</a> with "input", |inputType| and |data|
</div><!-- algorithm -->
<div class="algorithm" data-algorithm="fire-an-inputevent">
<h3 id="fire an inputevent"><dfn>fire an InputEvent</dfn></h3>
: Input
:: |eventType|, a DOMString containing the event type
:: |inputType|, a DOMString containing the input event type
:: |data|, a DOMString containing event data
: Output
:: None
Issue: What about target ranges? Need to add support here.
Issue: The target for input events should consider focus, but should also ensure that
the element is editable and being modified.
Compare: <a>fire a compositionevent</a>
1. Let target =
<a href="https://html.spec.whatwg.org/#currently-focused-area-of-a-top-level-browsing-context">currently focused area of a top-level browsing context</a>
1. Let |event| = result of <a>create an InputEvent</a> with |eventType|, |target|
1. Set |event|.{{inputType}} = |inputType|
1. Set |event|.{{InputEvent/data}} = |data|
1. Return the result of <a>dispatch</a> |event| at |target|
</div><!-- algorithm -->
</section>
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<section>
<h2 id="keyboard event">Keyboard Event</h2>
<h3 id="keyboardevent-interface">KeyboardEvent Interface</h3>
A {{KeyboardEvent}} has the following:
<dl dfn-for="KeyboardEvent">
<li><dfn const>DOM_KEY_LOCATION_STANDARD</dfn></li>
<li><dfn const>DOM_KEY_LOCATION_LEFT</dfn></li>
<li><dfn const>DOM_KEY_LOCATION_RIGHT</dfn></li>
<li><dfn const>DOM_KEY_LOCATION_NUMPAD</dfn></li>
<li><dfn attribute>key</dfn></li>
<li><dfn attribute>code</dfn></li>
<li><dfn attribute>location</dfn></li>
<li><dfn attribute>ctrlKey</dfn></li>
<li><dfn attribute>shiftKey</dfn></li>
<li><dfn attribute>altKey</dfn></li>
<li><dfn attribute>metaKey</dfn></li>
<li><dfn attribute>repeat</dfn></li>
<li><dfn attribute>isComposing</dfn></li>
<li>getModifierState(keyArg) - handled by <a>get modifier state</a></li>
</dl>
Along with the following historical attributes:
<dl dfn-for="KeyboardEvent">
<li><dfn attribute>keyCode</dfn></li>
<li><dfn attribute>keyChar</dfn></li>
</dl>
And the following internal state:
<dl dfn-for="KeyboardEvent">
<li><dfn>shift flag</dfn></li>
<li><dfn>control flag</dfn></li>
<li><dfn>alt flag</dfn></li>
<li><dfn>altgraph flag</dfn></li>
<li><dfn>meta flag</dfn></li>
<li><dfn>capslock flag</dfn></li>
<li><dfn>numlock flag</dfn></li>
</dl>
<h3 id="keyboardevent-global-state">Global State for KeyboardEvent</h3>
<h4 id="keyboardevent-global-ua">User Agent-Level State</h4>
The UA must maintain the following values that are shared for the entire
User Agent.
A <dfn>key modifier state</dfn> (initially empty) that keeps track of the current
state of each <a>modifier key</a> available on the system.
<h4 id="keyboardevent-global-window">Window-Level State</h4>