Editorial: provide a shorthand for other specifications to create events

This can be useful when you can’t use fire, but need to initialize
event attributes in a particular manner or keep the event around for
some reason.

Author: annevk

dom.bs

@@ -942,25 +942,54 @@ method must, when invoked, run these steps:
 
 <h3 id=constructing-events>Constructing events</h3>
 
-When a <dfn export for=Event id=concept-event-constructor>constructor</dfn> of the
-{{Event}} interface, or of an interface that inherits from the {{Event}} interface, is
-invoked, these steps must be run:
+<p>When a <dfn export for=Event id=concept-event-constructor>constructor</dfn> of the {{Event}}
+interface, or of an interface that inherits from the {{Event}} interface, is invoked, these steps
+must be run, given the arguments <var>type</var> and <var>eventInitDict</var>:
 
 <ol>
- <li><p>Create an <a>event</a> that uses the interface the constructor was invoked upon.
+ <li><p>Create a new object <var>event</var> using this interface.
 
- <li><p>Set its <a>initialized flag</a>.
+ <li><p>Set <var>event</var>'s <a>initialized flag</a>.
 
- <li><p>Initialize the {{Event/type}} attribute to the <var>type</var> argument.
+ <li><p>Initialize <var>event</var>'s {{Event/type}} attribute to <var>type</var>.
 
- <li><p>If there is an <var>eventInitDict</var> argument, then for each <a>dictionary member</a>
- present, find the attribute on <a>event</a> whose <a spec=webidl>identifier</a> matches the key of
- the <a>dictionary member</a> and then set the attribute to the value of that
+ <li><p>For each <a>dictionary member</a> present in <var>eventInitDict</var>, find the attribute on
+ <var>event</var> whose <a spec=webidl>identifier</a> matches the key of the
+ <a>dictionary member</a> and then set the attribute to the value of that <a>dictionary member</a>.
+
+ <li><p>Return <var>event</var>.
+</ol>
+
+<p>To
+<dfn export id=concept-event-create lt="creating an event|create an event">create an event</dfn>
+using <var>eventInterface</var>, which must be either {{Event}} or an interface that inherits from
+it, run these steps:</p>
+
+<ol>
+ <li><p>Create a new object <var>event</var> using <var>eventInterface</var>.
+
+ <li><p>Set <var>event</var>'s <a>initialized flag</a>.
+
+ <li><p>Let <var>defaultEventInitDict</var> be the result of
+ <a lt="converted to an IDL value">converting</a> the JavaScript value undefined to the dictionary
+ type accepted by <var>eventInterface</var>'s constructor. (This dictionary type will either be
+ {{EventInit}} or a dictionary that inherits from it.)
+
+ <li>For each <a>dictionary member</a> present in <var>defaultEventInitDict</var>, find the
+ attribute on <var>event</var> whose <a spec=webidl>identifier</a> matches the key of the
+ <a>dictionary member</a> and then set the attribute to the default value of that
  <a>dictionary member</a>.
 
- <li><p>Return the <a>event</a>.
+ <li><p>Initialize <var>event</var>'s {{Event/isTrusted}} attribute to true.
+
+ <li><p>Return <var>event</var>.
 </ol>
 
+<p class=note><a>Create an event</a> is meant to be used by other specifications which need to
+separately <a lt="create an event">create</a> and <a>dispatch</a> events, instead of simply
+<a lt="fire an event">firing</a> them. It ensures the event's attributes are initialized to the
+correct defaults.</p>
+
 
 <h3 id=defining-event-interfaces>Defining event interfaces</h3>
 
@@ -1447,10 +1476,10 @@ initialized, and a <var>legacy target override flag</var>, run these steps:
  <li><p>If <var>eventConstructor</var> is not given, then let <var>eventConstructor</var> be
  {{Event}}.
 
- <li><p>Let <var>event</var> be the result of <a for=Event lt=constructor>invoking</a> the initial
- value of <var>eventConstructor</var> with the argument <var>e</var>.
+ <li><p>Let <var>event</var> be the result of <a>creating an event</a> given
+ <var>eventConstructor</var>.
 
- <li><p>Initialize <var>event</var>'s {{Event/isTrusted}} attribute to true.
+ <li><p>Initialize <var>event</var>'s {{Event/type}} attribute to <var>e</var>.
 
  <li>
   <p>Initialize any other IDL attributes of <var>event</var> as described in the invocation of this
@@ -5199,15 +5228,17 @@ invoked, must run these steps:
  <li><p>If <var>constructor</var> is null, then <a>throw</a> a {{NotSupportedError}}.
 
  <li>
-  <p>If the initial value of <var>constructor</var> is undefined, then <a>throw</a> a
-  {{NotSupportedError}}.
+  <p>If the interface indicated by <var>constructor</var> is not exposed on the <a>relevant global
+  object</a> of the <a>context object</a>, then <a>throw</a> a {{NotSupportedError}}.
 
   <p class=note>Typically user agents disable support for touch events in some configurations, in
-  which case the initial value of {{TouchEvent}} is undefined.
+  which case this clause would be triggered for the interface {{TouchEvent}}.
+
+ <li><p>Let <var>event</var> be the result of <a>creating an event</a> given <var>constructor</var>.
 
- <li><p>Let <var>event</var> be the result of <a for=Event lt=constructor>invoking</a> the initial
- value of <var>constructor</var> with the empty string as argument.
- <!-- "initial value" as in before script could get to it -->
+ <li><p>Initialize <var>event</var>'s {{Event/type}} attribute to the empty string.
+
+ <li><p>Initialize <var>event</var>'s {{Event/isTrusted}} attribute to false.
 
  <li><p>Unset <var>event</var>'s <a>initialized flag</a>.
 

dom.html

@@ -713,21 +713,40 @@ <h3 class="heading settled" data-level="3.3" id="interface-customevent"><span cl
     <li>Set <a data-link-type="dfn" href="#context-object">context object</a>’s <code class="idl"><a data-link-type="idl" href="#dom-customevent-detail">detail</a></code> attribute to <var>detail</var>. 
    </ol>
    <h3 class="heading settled" data-level="3.4" id="constructing-events"><span class="secno">3.4. </span><span class="content">Constructing events</span><a class="self-link" href="#constructing-events"></a></h3>
-   <p>When a <dfn data-dfn-for="Event" data-dfn-type="dfn" data-export="" id="concept-event-constructor">constructor<a class="self-link" href="#concept-event-constructor"></a></dfn> of the <code class="idl"><a data-link-type="idl" href="#event">Event</a></code> interface, or of an interface that inherits from the <code class="idl"><a data-link-type="idl" href="#event">Event</a></code> interface, is
-invoked, these steps must be run:</p>
+   <p>When a <dfn data-dfn-for="Event" data-dfn-type="dfn" data-export="" id="concept-event-constructor">constructor<a class="self-link" href="#concept-event-constructor"></a></dfn> of the <code class="idl"><a data-link-type="idl" href="#event">Event</a></code> interface, or of an interface that inherits from the <code class="idl"><a data-link-type="idl" href="#event">Event</a></code> interface, is invoked, these steps
+must be run, given the arguments <var>type</var> and <var>eventInitDict</var>: </p>
    <ol>
     <li>
-     <p>Create an <a data-link-type="dfn" href="#concept-event">event</a> that uses the interface the constructor was invoked upon. </p>
+     <p>Create a new object <var>event</var> using this interface. </p>
     <li>
-     <p>Set its <a data-link-type="dfn" href="#initialized-flag">initialized flag</a>. </p>
+     <p>Set <var>event</var>’s <a data-link-type="dfn" href="#initialized-flag">initialized flag</a>. </p>
     <li>
-     <p>Initialize the <code class="idl"><a data-link-type="idl" href="#dom-event-type">type</a></code> attribute to the <var>type</var> argument. </p>
+     <p>Initialize <var>event</var>’s <code class="idl"><a data-link-type="idl" href="#dom-event-type">type</a></code> attribute to <var>type</var>. </p>
     <li>
-     <p>If there is an <var>eventInitDict</var> argument, then for each <a data-link-type="dfn" href="https://heycam.github.io/webidl/#dfn-dictionary-member">dictionary member</a> present, find the attribute on <a data-link-type="dfn" href="#concept-event">event</a> whose <a data-link-type="dfn" href="https://heycam.github.io/webidl/#dfn-identifier">identifier</a> matches the key of
- the <a data-link-type="dfn" href="https://heycam.github.io/webidl/#dfn-dictionary-member">dictionary member</a> and then set the attribute to the value of that <a data-link-type="dfn" href="https://heycam.github.io/webidl/#dfn-dictionary-member">dictionary member</a>. </p>
+     <p>For each <a data-link-type="dfn" href="https://heycam.github.io/webidl/#dfn-dictionary-member">dictionary member</a> present in <var>eventInitDict</var>, find the attribute on <var>event</var> whose <a data-link-type="dfn" href="https://heycam.github.io/webidl/#dfn-identifier">identifier</a> matches the key of the <a data-link-type="dfn" href="https://heycam.github.io/webidl/#dfn-dictionary-member">dictionary member</a> and then set the attribute to the value of that <a data-link-type="dfn" href="https://heycam.github.io/webidl/#dfn-dictionary-member">dictionary member</a>. </p>
     <li>
-     <p>Return the <a data-link-type="dfn" href="#concept-event">event</a>. </p>
+     <p>Return <var>event</var>. </p>
+   </ol>
+   <p>To <dfn data-dfn-type="dfn" data-export="" data-lt="creating an event|create an event" id="concept-event-create">create an event<a class="self-link" href="#concept-event-create"></a></dfn> using <var>eventInterface</var>, which must be either <code class="idl"><a data-link-type="idl" href="#event">Event</a></code> or an interface that inherits from
+it, run these steps:</p>
+   <ol>
+    <li>
+     <p>Create a new object <var>event</var> using <var>eventInterface</var>. </p>
+    <li>
+     <p>Set <var>event</var>’s <a data-link-type="dfn" href="#initialized-flag">initialized flag</a>. </p>
+    <li>
+     <p>Let <var>defaultEventInitDict</var> be the result of <a data-link-type="dfn" href="https://heycam.github.io/webidl/#dfn-convert-ecmascript-to-idl-value">converting</a> the JavaScript value undefined to the dictionary
+ type accepted by <var>eventInterface</var>’s constructor. (This dictionary type will either be <code class="idl"><a data-link-type="idl" href="#dictdef-eventinit">EventInit</a></code> or a dictionary that inherits from it.) </p>
+    <li>For each <a data-link-type="dfn" href="https://heycam.github.io/webidl/#dfn-dictionary-member">dictionary member</a> present in <var>defaultEventInitDict</var>, find the
+ attribute on <var>event</var> whose <a data-link-type="dfn" href="https://heycam.github.io/webidl/#dfn-identifier">identifier</a> matches the key of the <a data-link-type="dfn" href="https://heycam.github.io/webidl/#dfn-dictionary-member">dictionary member</a> and then set the attribute to the default value of that <a data-link-type="dfn" href="https://heycam.github.io/webidl/#dfn-dictionary-member">dictionary member</a>. 
+    <li>
+     <p>Initialize <var>event</var>’s <code class="idl"><a data-link-type="idl" href="#dom-event-istrusted">isTrusted</a></code> attribute to true. </p>
+    <li>
+     <p>Return <var>event</var>. </p>
    </ol>
+   <p class="note" role="note"><a data-link-type="dfn" href="#concept-event-create">Create an event</a> is meant to be used by other specifications which need to
+separately <a data-link-type="dfn" href="#concept-event-create">create</a> and <a data-link-type="dfn" href="#concept-event-dispatch">dispatch</a> events, instead of simply <a data-link-type="dfn" href="#concept-event-fire">firing</a> them. It ensures the event’s attributes are initialized to the
+correct defaults.</p>
    <h3 class="heading settled" data-level="3.5" id="defining-event-interfaces"><span class="secno">3.5. </span><span class="content">Defining event interfaces</span><a class="self-link" href="#defining-event-interfaces"></a></h3>
    <p>In general, when defining a new interface that inherits from <code class="idl"><a data-link-type="idl" href="#event">Event</a></code> please always ask
 feedback from the <a href="https://whatwg.org/">WHATWG</a> or the <a href="https://www.w3.org/2008/webapps/">W3C WebApps WG</a> community.</p>
@@ -1070,10 +1089,9 @@ <h3 class="heading settled" data-level="3.9" id="firing-events"><span class="sec
     <li>
      <p>If <var>eventConstructor</var> is not given, then let <var>eventConstructor</var> be <code class="idl"><a data-link-type="idl" href="#event">Event</a></code>. </p>
     <li>
-     <p>Let <var>event</var> be the result of <a data-link-type="dfn" href="#concept-event-constructor">invoking</a> the initial
- value of <var>eventConstructor</var> with the argument <var>e</var>. </p>
+     <p>Let <var>event</var> be the result of <a data-link-type="dfn" href="#concept-event-create">creating an event</a> given <var>eventConstructor</var>. </p>
     <li>
-     <p>Initialize <var>event</var>’s <code class="idl"><a data-link-type="idl" href="#dom-event-istrusted">isTrusted</a></code> attribute to true. </p>
+     <p>Initialize <var>event</var>’s <code class="idl"><a data-link-type="idl" href="#dom-event-type">type</a></code> attribute to <var>e</var>. </p>
     <li>
      <p>Initialize any other IDL attributes of <var>event</var> as described in the invocation of this
   algorithm. </p>
@@ -3264,12 +3282,16 @@ <h3 class="heading settled" data-level="4.5" id="interface-document"><span class
     <li>
      <p>If <var>constructor</var> is null, then <a data-link-type="dfn" href="https://heycam.github.io/webidl/#dfn-throw">throw</a> a <code class="idl"><a data-link-type="idl" href="https://heycam.github.io/webidl/#notsupportederror">NotSupportedError</a></code>. </p>
     <li>
-     <p>If the initial value of <var>constructor</var> is undefined, then <a data-link-type="dfn" href="https://heycam.github.io/webidl/#dfn-throw">throw</a> a <code class="idl"><a data-link-type="idl" href="https://heycam.github.io/webidl/#notsupportederror">NotSupportedError</a></code>. </p>
+     <p>If the interface indicated by <var>constructor</var> is not exposed on the <a data-link-type="dfn" href="https://html.spec.whatwg.org/multipage/webappapis.html#concept-relevant-global">relevant global
+  object</a> of the <a data-link-type="dfn" href="#context-object">context object</a>, then <a data-link-type="dfn" href="https://heycam.github.io/webidl/#dfn-throw">throw</a> a <code class="idl"><a data-link-type="idl" href="https://heycam.github.io/webidl/#notsupportederror">NotSupportedError</a></code>. </p>
      <p class="note" role="note">Typically user agents disable support for touch events in some configurations, in
-  which case the initial value of <code class="idl"><a data-link-type="idl" href="https://www.w3.org/TR/touch-events/#touchevent-interface">TouchEvent</a></code> is undefined. </p>
+  which case this clause would be triggered for the interface <code class="idl"><a data-link-type="idl" href="https://www.w3.org/TR/touch-events/#touchevent-interface">TouchEvent</a></code>. </p>
     <li>
-     <p>Let <var>event</var> be the result of <a data-link-type="dfn" href="#concept-event-constructor">invoking</a> the initial
- value of <var>constructor</var> with the empty string as argument. </p>
+     <p>Let <var>event</var> be the result of <a data-link-type="dfn" href="#concept-event-create">creating an event</a> given <var>constructor</var>. </p>
+    <li>
+     <p>Initialize <var>event</var>’s <code class="idl"><a data-link-type="idl" href="#dom-event-type">type</a></code> attribute to the empty string. </p>
+    <li>
+     <p>Initialize <var>event</var>’s <code class="idl"><a data-link-type="idl" href="#dom-event-istrusted">isTrusted</a></code> attribute to false. </p>
     <li>
      <p>Unset <var>event</var>’s <a data-link-type="dfn" href="#initialized-flag">initialized flag</a>. </p>
     <li>
@@ -5811,6 +5833,7 @@ <h3 class="no-num no-ref heading settled" id="index-defined-here"><span class="c
    <li><a href="#converted-to-ascii-uppercase">converted to ASCII uppercase</a><span>, in §2.2</span>
    <li><a href="#converting-nodes-into-a-node">converting nodes into a node</a><span>, in §4.2.6</span>
    <li><a href="#concept-create-element">create an element</a><span>, in §4.9</span>
+   <li><a href="#concept-event-create">create an event</a><span>, in §3.4</span>
    <li><a href="#dom-document-createattribute">createAttribute(localName)</a><span>, in §4.5</span>
    <li><a href="#dom-document-createattributens">createAttributeNS(namespace, qualifiedName)</a><span>, in §4.5</span>
    <li><a href="#dom-document-createcdatasection">createCDATASection(data)</a><span>, in §4.5</span>
@@ -5837,6 +5860,7 @@ <h3 class="no-num no-ref heading settled" id="index-defined-here"><span class="c
    <li><a href="#dom-document-createtreewalker">createTreeWalker(root, whatToShow)</a><span>, in §4.5</span>
    <li><a href="#dom-document-createtreewalker">createTreeWalker(root, whatToShow, filter)</a><span>, in §4.5</span>
    <li><a href="#concept-create-element">creating an element</a><span>, in §4.9</span>
+   <li><a href="#concept-event-create">creating an event</a><span>, in §3.4</span>
    <li><a href="#dom-treewalker-currentnode">currentNode</a><span>, in §6.2</span>
    <li><a href="#dom-event-currenttarget">currentTarget</a><span>, in §3.2</span>
    <li><a href="#concept-element-custom">custom</a><span>, in §4.9</span>
@@ -6665,6 +6689,7 @@ <h3 class="no-num no-ref heading settled" id="index-defined-elsewhere"><span cla
      <li><a href="https://heycam.github.io/webidl/#wrongdocumenterror">WrongDocumentError</a>
      <li><a href="https://heycam.github.io/webidl/#call-a-user-objects-operation">call a user object's operation</a>
      <li><a href="https://heycam.github.io/webidl/#dfn-callback-this-value">callback this value</a>
+     <li><a href="https://heycam.github.io/webidl/#dfn-convert-ecmascript-to-idl-value">converted to an idl value</a>
      <li><a href="https://heycam.github.io/webidl/#dfn-dictionary-member">dictionary members</a>
      <li><a href="https://heycam.github.io/webidl/#dfn-identifier">identifier</a>
      <li><a href="https://heycam.github.io/webidl/#invoke-a-callback-function">invoke</a>