[css-scroll-snap] [cssom-view] Use a single scroll queue for all events

Fixes #11164

Author: emilio

css-scroll-snap-2/Overview.bs

@@ -345,9 +345,6 @@ Snap Targets</h4>
 	scrolling operation also results in a {{scrollsnapchange}} event being fired, the
 	{{scrollsnapchange}} event should be fired before the {{scrollend}} event.
 
-	Each {{Document}} has an associated list of
-	<dfn export for=Document>pending scrollsnapchange event targets</dfn>, initially empty.
-
 	Each
 	<a spec=css-scroll-snap lt="scroll snap container">snap container</a> has
 	one <dfn export>scrollsnapchangeTargetBlock</dfn> and one
@@ -378,32 +375,17 @@ Snap Targets</h4>
 			<var>inlineScrollSnapchangingTarget</var>.
 		1. Set <var>snap targets changed</var> to true.
 	1. If <var>snap targets changed</var> is true:
-		1. If |snapcontainer| is not already in <var>doc</var>'s
-			<a>pending scrollsnapchange event targets</a>:
-			1. Append |snapcontainer| to <var>doc</var>'s
-				<a>pending scrollsnapchange event targets</a>.
+		1. If (|snapcontainer|, <code>"scrollsnapchange"</code>) is not already in <var>doc</var>'s
+			<a>pending scroll events</a>:
+			1. Append (|snapcontainer|, <code>"scrollsnapchange"</code>) to <var>doc</var>'s
+				<a>pending scroll events</a>.
 
 	Note: When snapping occurs on a scroller (either due to a layout change or a
 	scrolling operation) the <a>scrollsnapchanging block-axis target</a> and <a>scrollsnapchanging inline-axis target</a>
 	associated with that scroller are updated and represent the current snap targets
 	of that scroller. This allows the <a>update scrollsnapchange targets</a> algorithm
 	to use these [=snap targets=] to determine whether a {{scrollsnapchange}} event should be fired.
 
-	When asked to <dfn export for=Document>dispatch pending scrollsnapchange events</dfn> for a {{Document}},
-		<var>doc</var>, run these steps:
-	1. For each item <var>target</var> in |doc|'s <a>pending scrollsnapchange event targets</a>:
-		1. Let |blockTarget| and |inlineTarget| be null initially.
-		1. If the <a>scrollsnapchangeTargetBlock</a> associated with <var>target</var> is a pseudo-element,
-			set |blockTarget| to the owning element of that <a>scrollsnapchangeTargetBlock</a>.
-		1. Otherwise, set |blockTarget| to that <a>scrollsnapchangeTargetBlock</a>.
-		1. If the <a>scrollsnapchangeTargetInline</a> associated with <var>target</var> is a pseudo-element,
-			set |inlineTarget| to the owning element of that <a>scrollsnapchangeTargetInline</a>.
-		1. Otherwise, Set |inlineTarget| to that <a>scrollsnapchangeTargetInline</a>.
-		1. Fire a {{SnapEvent}}, |snapevent|, named {{scrollsnapchange}} at <var>target</var>
-			and let |snapevent|'s {{SnapEvent/snapTargetBlock}} and
-			{{SnapEvent/snapTargetInline}} attributes be |blockTarget| and |inlineTarget| respectively.
-	1. Empty <var>doc</var>'s <a>pending scrollsnapchange event targets</a>.
-
 	<h4 id="scrollsnapchanging"> scrollsnapchanging </h4>
 	{{scrollsnapchanging}} is dispatched:
 	* during a scrolling operation, if the [=snap targets=] to which a
@@ -437,12 +419,6 @@ Snap Targets</h4>
 	will be possible for subsequent scrolling input to further alter the snap
 	container's scroll position and result in a different eventual snap target.
 
-
-	{{scrollsnapchanging}} events are fired before {{scroll!!event}} events.
-
-	Each {{Document}} has an associated list of
-	<dfn export for=Document>pending scrollsnapchanging event targets</dfn>, initially empty.
-
 	Each
 	<a spec=css-scroll-snap lt="scroll snap container">snap container</a> has
 	one <dfn>scrollsnapchanging block-axis target</dfn>
@@ -463,32 +439,17 @@ Snap Targets</h4>
 	1. If <var>newBlockTarget</var> is not the same [=snap target=] as <var>blockTarget</var>:
 		1. Set the <a>scrollsnapchanging block-axis target</a> associated with |snapcontainer| to
 			<var>newBlockTarget</var>.
-		1. If |snapcontainer| is not already in <var>doc</var>'s
-			<a>pending scrollsnapchanging event targets</a>,
-			1. Append |snapcontainer| to <var>doc</var>'s
-				<a>pending scrollsnapchanging event targets</a>
+		1. If (|snapcontainer|, <code>"scrollsnapchanging"</code>) is not already in <var>doc</var>'s
+			<a>pending scroll events</a>,
+			1. Append (|snapcontainer|, <code>"scrollsnapchanging"</code>) to <var>doc</var>'s
+				<a>pending scroll events</a>
 	1. If <var>newInlineTarget</var> is not the same [=snap target=] as <var>inlineTarget</var>:
 		1. Set the <a>scrollsnapchanging inline-axis target</a> associated with |snapcontainer| to
 			<var>newInlineTarget</var>.
-		1. If |snapcontainer| is not already in <var>doc</var>'s
-			<a>pending scrollsnapchanging event targets</a>,
-			1. Append |snapcontainer| to <var>doc</var>'s
-				<a>pending scrollsnapchanging event targets</a>.
-
-	When asked to <dfn export for=Document>dispatch pending scrollsnapchanging events</dfn> for a {{Document}},
-		<var>doc</var>, run these steps:
-	1. For each item <var>target</var> in |doc|'s <a>pending scrollsnapchanging event targets</a>:
-		1. Let |blockTarget| and |inlineTarget| be null initially.
-		1. If the <a>scrollsnapchanging block-axis target</a> associated with <var>target</var> is a pseudo-element,
-			set |blockTarget| to the owning element of that <a>scrollsnapchanging block-axis target</a>.
-		1. Otherwise, set |blockTarget| to that <a>scrollsnapchanging block-axis target</a>.
-		1. If the <a>scrollsnapchanging inline-axis target</a> associated with <var>target</var> is a pseudo-element,
-			set |inlineTarget| to the owning element of that <a>scrollsnapchanging inline-axis target</a>.
-		1. Otherwise, set |inlineTarget| to that <a>scrollsnapchanging inline-axis target</a>.
-		1. Fire a {{SnapEvent}}, |snapevent|, named {{scrollsnapchanging}} at <var>target</var>
-			and let |snapevent|'s {{SnapEvent/snapTargetBlock}} and
-			{{SnapEvent/snapTargetInline}} attributes be |blockTarget| and |inlineTarget|, respectively.
-	1. Empty <var>doc</var>'s <a>pending scrollsnapchanging event targets</a>.
+		1. If (|snapcontainer|, <code>"scrollsnapchanging"</code>) is not already in <var>doc</var>'s
+			<a>pending scroll events</a>,
+			1. Append (|snapcontainer|, <code>"scrollsnapchanging"</code>) to <var>doc</var>'s
+				<a>pending scroll events</a>
 
 	<h4 id="snap-events-on-layout-changes">Snap Events due to Layout Changes </h4>
 	When a <a spec=css-scroll-snap lt="scroll snap container">snap container</a>,

cssom-view-1/Overview.bs

@@ -2304,9 +2304,7 @@ When asked to <dfn export for=Document>run the resize steps</dfn> for a {{Docume
 
 This section integrates with the <a for=/>event loop</a> defined in HTML. [[!HTML]]
 
-Each {{Document}} has an associated list of <dfn for=Document>pending scroll event targets</dfn>, initially empty.
-
-Each {{Document}} has an associated list of <dfn for=Document>pending scrollend event targets</dfn>, initially empty.
+Each {{Document}} has an associated list of <dfn for=Document>pending scroll events</dfn>, which stores pairs of ({{EventTarget}}, {{DOMString}}), initially empty.
 
 Whenever a <a>viewport</a> gets scrolled (whether in response to user interaction or by an API), the user agent must run these steps:
 
@@ -2316,8 +2314,8 @@ Whenever a <a>viewport</a> gets scrolled (whether in response to user interactio
     for <var>doc</var> with <var>doc</var>'s <a spec="css-scroll-snap-2">eventual snap target</a> in the block axis
     as newBlockTarget and <var>doc</var>'s <a spec="css-scroll-snap-2">eventual snap target</a> in the inline axis
     as newInlineTarget.
-1. If <var>doc</var> is already in <var>doc</var>'s <a>pending scroll event targets</a>, abort these steps.
-1. Append <var>doc</var> to <var>doc</var>'s <a>pending scroll event targets</a>.
+1. If (<var>doc</var>, <code>"scroll"</code>) is already in <var>doc</var>'s <a>pending scroll events</a>, abort these steps.
+1. Append (<var>doc</var>, <code>"scroll"</code>) to <var>doc</var>'s <a>pending scroll events</a>.
 
 Whenever an element gets scrolled (whether in response to user interaction or by an API), the user agent must run these steps:
 
@@ -2327,29 +2325,18 @@ Whenever an element gets scrolled (whether in response to user interaction or by
     for the element with the element's <a spec="css-scroll-snap-2">eventual snap target</a> in the block axis
     as newBlockTarget and the element's <a spec="css-scroll-snap-2">eventual snap target</a> in the inline axis
     as newInlineTarget.
-1. If the element is already in <var>doc</var>'s <a>pending scroll event targets</a>, abort these steps.
-1. Append the element to <var>doc</var>'s <a>pending scroll event targets</a>.
+1. If the element is already in <var>doc</var>'s <a>pending scroll events</a>, abort these steps.
+1. Append the element to <var>doc</var>'s <a>pending scroll events</a>.
 
 Whenever a <a>visual viewport</a> gets scrolled (whether in response to user interaction or by an API), the user agent must run these steps:
 
 1. Let <var>vv</var> be the {{VisualViewport}} object that was scrolled.
 1. Let <var>doc</var> be <var>vv</var>'s <a for=visualviewport>associated document</a>.
-1. If <var>vv</var> is already in <var>doc</var>'s <a>pending scroll event targets</a>, abort these steps.
-1. Append <var>vv</var> to <var>doc</var>'s <a>pending scroll event targets</a>.
+1. If (<var>vv</var>, <code>"scroll"</code>) is already in <var>doc</var>'s <a>pending scroll events</a>, abort these steps.
+1. Append (<var>vv</var>, <code>"scroll"</code>) to <var>doc</var>'s <a>pending scroll events</a>.
 
 When asked to <dfn export for=Document>run the scroll steps</dfn> for a {{Document}} <var>doc</var>, run these steps:
 
-1. Run the steps to <a spec="css-scroll-snap-2">dispatch pending scrollsnapchanging events</a> for <var>doc</var>.
-1. For each item <var>target</var> in <var>doc</var>'s <a>pending scroll event targets</a>,
-    in the order they were added to the list, run these substeps:
-
-    1. If <var>target</var> is a {{Document}}, <a>fire an event</a> named <a event>scroll</a> that bubbles at <var>target</var>.
-    1. Otherwise, <a>fire an event</a> named <a event>scroll</a> at <var>target</var>.
-1. Empty <var>doc</var>'s <a>pending scroll event targets</a>.
-1. Run the steps to <a spec="css-scroll-snap-2">dispatch pending scrollsnapchange events</a> for <var>doc</var>.
-
-Whenever scrolling is <a lt="scroll completed">completed</a>, the user agent must run these steps:
-
 Issue: In what order are scrollend events dispatched? Ordered based on scroll start or scroll completion?
 
 1. For each scrolling box <var>box</var> that was scrolled:
@@ -2358,13 +2345,40 @@ Issue: In what order are scrollend events dispatched? Ordered based on scroll st
         be the {{VisualViewport}}. Otherwise, <var>box</var> belongs to an element and let <var>doc</var> be the element's <a>node document</a> and <var>target</var> be the element.
     1. If <var>box</var> belongs to a <a spec=css-scroll-snap lt="scroll snap container">snap container</a>, |snapcontainer|,
         run the <a spec=css-scroll-snap-2 lt="update scrollsnapchange targets">update scrollsnapchange targets</a> steps for |snapcontainer|.
-    1. If <var>target</var> is already in <var>doc</var>'s <a>pending scrollend event targets</a>, abort these steps.
-    1. Append <var>target</var> to <var>doc</var>'s <a>pending scrollend event targets</a>.
-1. Run the steps to <a spec="css-scroll-snap-2">dispatch pending scrollsnapchange targets</a> for <var>doc</var>.
-1. For each item <var>target</var> in <var>doc</var>'s <a>pending scrollend event targets</a>, in the order they were added to the list, run these substeps:
-    1. If <var>target</var> is a {{Document}}, <a>fire an event</a> named <a event>scrollend</a> that bubbles at <var>target</var>.
-    1. Otherwise, <a>fire an event</a> named <a event>scrollend</a> at <var>target</var>.
-1. Empty <var>doc</var>'s <a>pending scrollend event targets</a>.
+    1. If (<var>target</var>, <code>"scrollend"</code>) is already in <var>doc</var>'s <a>pending scroll events</a>, abort these steps.
+    1. Append (<var>target</var>, <code>"scrollend"</code>) to <var>doc</var>'s <a>pending scroll events</a>.
+
+1. For each item (<var>target</var>, <var>type</var>) in <var>doc</var>'s <a>pending scroll events</a>,
+    in the order they were added to the list, run these substeps:
+
+    1. If <var>target</var> is a {{Document}}, and <var>type</var> is <code>"scroll"</code> or <code>"scrollend"</code>,
+        <a>fire an event</a> named <a event>scroll</a> that bubbles at <var>target</var>.
+    1. Otherwise, if <var>type</var> is <code>"scrollsnapchange"</code>, then:
+      1. Let |blockTarget| and |inlineTarget| be null initially.
+      1. If the <a>scrollsnapchangeTargetBlock</a> associated with <var>target</var> is a pseudo-element,
+        set |blockTarget| to the owning element of that <a>scrollsnapchangeTargetBlock</a>.
+      1. Otherwise, set |blockTarget| to that <a>scrollsnapchangeTargetBlock</a>.
+      1. If the <a>scrollsnapchangeTargetInline</a> associated with <var>target</var> is a pseudo-element,
+        set |inlineTarget| to the owning element of that <a>scrollsnapchangeTargetInline</a>.
+      1. Otherwise, Set |inlineTarget| to that <a>scrollsnapchangeTargetInline</a>.
+      1. Fire a {{SnapEvent}}, |snapevent|, named {{scrollsnapchange}} at <var>target</var>
+        and let |snapevent|'s {{SnapEvent/snapTargetBlock}} and
+        {{SnapEvent/snapTargetInline}} attributes be |blockTarget| and |inlineTarget| respectively.
+    1. Otherwise, if <var>type</var> is <code>"scrollsnapchanging"</code>, then:
+      1. Let |blockTarget| and |inlineTarget| be null initially.
+      1. If the <a>scrollsnapchanging block-axis target</a> associated with <var>target</var> is a pseudo-element,
+        set |blockTarget| to the owning element of that <a>scrollsnapchanging block-axis target</a>.
+      1. Otherwise, set |blockTarget| to that <a>scrollsnapchanging block-axis target</a>.
+      1. If the <a>scrollsnapchanging inline-axis target</a> associated with <var>target</var> is a pseudo-element,
+        set |inlineTarget| to the owning element of that <a>scrollsnapchanging inline-axis target</a>.
+      1. Otherwise, set |inlineTarget| to that <a>scrollsnapchanging inline-axis target</a>.
+      1. Fire a {{SnapEvent}}, |snapevent|, named {{scrollsnapchanging}} at <var>target</var>
+        and let |snapevent|'s {{SnapEvent/snapTargetBlock}} and
+        {{SnapEvent/snapTargetInline}} attributes be |blockTarget| and |inlineTarget|, respectively.
+    1. Otherwise, <a>fire an event</a> named <var>type</var> at <var>target</var>.
+1. Empty <var>doc</var>'s <a>pending scroll events</a>.
+
+Whenever scrolling is <a lt="scroll completed">completed</a>, the user agent must run these steps:
 
 <h3 id=event-summary>Event summary</h3>