[css-font-loading] Prevent a FontFaceSet from triggering load events every time there's any layout operation that might request fonts.

Author: tabatkins

css-font-loading/Overview.bs

@@ -504,7 +504,13 @@ The <code>FontFaceSet</code> Interface</h2>
 	Authors can use the events and methods defined here to allow greater control over actions
 	that are dependent upon the availability of specific fonts.
 
-	There are <dfn>no pending font loads</dfn> for a given {{FontFaceSet}} whenever all of the following are true:
+	There are <dfn>no pending font loads</dfn> for a given {{FontFaceSet}} whenever
+	none of its contained {{FontFace}} objects have a {{FontFace/status}} of <code>"loading"</code>.
+
+	For {{FontFaceSet}}s that are <a>font sources</a>,
+	in addition to the above constriant,
+	the following must all be true
+	for them to be considered as having <a>no pending font loads</a>:
 
 	<ul>
 		<li>
@@ -513,20 +519,12 @@ The <code>FontFaceSet</code> Interface</h2>
 		<li>
 			There are no pending stylesheet requests.
 
-		<li>
-			There are no <a>available font faces</a>
-			with a {{FontFace/status}} of "loading".
-
 		<li>
 			There are no pending layout operations which might cause the user agent to request a font.
 	</ul>
 
-	If any of the above conditions are false,
-	there are <dfn>possibly pending font loads</dfn>.
-
-	Issue: The above is wrong; it assumes that you're only asking about the <a>font source</a>.
-	The {{FontFaceSet/status}} promise needs to pay attention to what {{FontFaceSet}} it's attached to.
-	I guess only the <a>font source's</a> {{FontFaceSet/status}} promise should care about pending layout operations.
+	If a {{FontFaceSet}} can't be considered to have <a>no pending font loads</a>,
+	it instead has <dfn>possibly pending font loads</dfn>.
 
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@@ -584,7 +582,7 @@ Events</h3>
 			The {{FontFaceSetLoadEvent/fontfaces}} attribute is initialized to the given list of {{FontFace}} objects.
 	</ol>
 
-	Whenever one or more <a>available font faces</a> for a given {{FontFaceSet}}
+	Whenever one or more {{FontFace}} objects within a given {{FontFaceSet}}
 	change their {{FontFace/status}} attribute to "loading",
 	the user agent must run the following steps:
 
@@ -634,6 +632,12 @@ Events</h3>
 	user agents must run these steps:
 
 	<ol>
+		<li>
+			If this is not the first time the {{FontFaceSet}} has had <a>no pending font loads</a>,
+			and none of its contained {{FontFace}} objects began loading
+			since the last time it had <a>no pending font loads</a>,
+			abort this algorithm.
+
 		<li>
 			Set <var>font face set's</var> {{FontFaceSet/status}} attribute to "loaded".
 

css-font-loading/Overview.html

@@ -573,7 +573,13 @@ <h2 class="heading settled" data-level=3 id=FontFaceSet-interface><span class=se
 	Authors can use the events and methods defined here to allow greater control over actions
 	that are dependent upon the availability of specific fonts.</p>
 
-<p>There are <dfn data-dfn-type=dfn data-noexport="" id=no-pending-font-loads>no pending font loads<a class=self-link href=#no-pending-font-loads></a></dfn> for a given <code class=idl><a data-link-type=idl href=#dom-fontfaceset title=FontFaceSet>FontFaceSet</a></code> whenever all of the following are true:</p>
+<p>There are <dfn data-dfn-type=dfn data-noexport="" id=no-pending-font-loads>no pending font loads<a class=self-link href=#no-pending-font-loads></a></dfn> for a given <code class=idl><a data-link-type=idl href=#dom-fontfaceset title=FontFaceSet>FontFaceSet</a></code> whenever
+	none of its contained <code class=idl><a data-link-type=idl href=#dom-fontface title=FontFace>FontFace</a></code> objects have a <code class=idl><a data-link-for=FontFace data-link-type=idl href=#dom-fontface-status title=status>status</a></code> of <code>"loading"</code>.</p>
+
+<p>For <code class=idl><a data-link-type=idl href=#dom-fontfaceset title=FontFaceSet>FontFaceSet</a></code>s that are <a data-link-type=dfn href=#font-source title="font sources">font sources</a>,
+	in addition to the above constriant,
+	the following must all be true
+	for them to be considered as having <a data-link-type=dfn href=#no-pending-font-loads title="no pending font loads">no pending font loads</a>:</p>
 
 	<ul>
 		<li>
@@ -582,20 +588,12 @@ <h2 class="heading settled" data-level=3 id=FontFaceSet-interface><span class=se
 		<li>
 			There are no pending stylesheet requests.
 
-		<li>
-			There are no <a data-link-type=dfn href=#available-font-faces title="available font faces">available font faces</a>
-			with a <code class=idl><a data-link-for=FontFace data-link-type=idl href=#dom-fontface-status title=status>status</a></code> of "loading".
-
 		<li>
 			There are no pending layout operations which might cause the user agent to request a font.
 	</ul>
 
-<p>If any of the above conditions are false,
-	there are <dfn data-dfn-type=dfn data-noexport="" id=possibly-pending-font-loads>possibly pending font loads<a class=self-link href=#possibly-pending-font-loads></a></dfn>.</p>
-
-<p class=issue id=issue-8f48960a><a class=self-link href=#issue-8f48960a></a>The above is wrong; it assumes that you’re only asking about the <a data-link-type=dfn href=#font-source title="font source">font source</a>.
-	The <code class=idl><a data-link-for=FontFaceSet data-link-type=idl href=#dom-fontfaceset-status title=status>status</a></code> promise needs to pay attention to what <code class=idl><a data-link-type=idl href=#dom-fontfaceset title=FontFaceSet>FontFaceSet</a></code> it’s attached to.
-	I guess only the <a data-link-type=dfn href=#font-source title="font source’s">font source’s</a> <code class=idl><a data-link-for=FontFaceSet data-link-type=idl href=#dom-fontfaceset-status title=status>status</a></code> promise should care about pending layout operations.</p>
+<p>If a <code class=idl><a data-link-type=idl href=#dom-fontfaceset title=FontFaceSet>FontFaceSet</a></code> can’t be considered to have <a data-link-type=dfn href=#no-pending-font-loads title="no pending font loads">no pending font loads</a>,
+	it instead has <dfn data-dfn-type=dfn data-noexport="" id=possibly-pending-font-loads>possibly pending font loads<a class=self-link href=#possibly-pending-font-loads></a></dfn>.</p>
 
 
 
@@ -645,7 +643,7 @@ <h3 class="heading settled" data-level=3.1 id=FontFaceSet-events><span class=sec
 			The <code class=idl><a data-link-for=FontFaceSetLoadEvent data-link-type=idl href=#dom-fontfacesetloadevent-fontfaces title=fontfaces>fontfaces</a></code> attribute is initialized to the given list of <code class=idl><a data-link-type=idl href=#dom-fontface title=FontFace>FontFace</a></code> objects.
 	</ol>
 
-<p>Whenever one or more <a data-link-type=dfn href=#available-font-faces title="available font faces">available font faces</a> for a given <code class=idl><a data-link-type=idl href=#dom-fontfaceset title=FontFaceSet>FontFaceSet</a></code>
+<p>Whenever one or more <code class=idl><a data-link-type=idl href=#dom-fontface title=FontFace>FontFace</a></code> objects within a given <code class=idl><a data-link-type=idl href=#dom-fontfaceset title=FontFaceSet>FontFaceSet</a></code>
 	change their <code class=idl><a data-link-for=FontFace data-link-type=idl href=#dom-fontface-status title=status>status</a></code> attribute to "loading",
 	the user agent must run the following steps:</p>
 
@@ -695,6 +693,12 @@ <h3 class="heading settled" data-level=3.1 id=FontFaceSet-events><span class=sec
 	user agents must run these steps:</p>
 
 	<ol>
+		<li>
+			If this is not the first time the <code class=idl><a data-link-type=idl href=#dom-fontfaceset title=FontFaceSet>FontFaceSet</a></code> has had <a data-link-type=dfn href=#no-pending-font-loads title="no pending font loads">no pending font loads</a>,
+			and none of its contained <code class=idl><a data-link-type=idl href=#dom-fontface title=FontFace>FontFace</a></code> objects began loading
+			since the last time it had <a data-link-type=dfn href=#no-pending-font-loads title="no pending font loads">no pending font loads</a>,
+			abort this algorithm.
+
 		<li>
 			Set <var>font face set’s</var> <code class=idl><a data-link-for=FontFaceSet data-link-type=idl href=#dom-fontfaceset-status title=status>status</a></code> attribute to "loaded".
 
@@ -1232,6 +1236,4 @@ <h2 class="no-num heading settled" id=references><span class=content>References<
 Should it be the url of the document?
 Is that correct for workers too,
 or should they use their worker url?
-Is that always defined?<a href=#issue-0c9d1948> ↵ </a></div><div class=issue>The above is wrong; it assumes that you’re only asking about the <a data-link-type=dfn href=#font-source title="font source">font source</a>.
-	The <code class=idl><a data-link-for=FontFaceSet data-link-type=idl href=#dom-fontfaceset-status title=status>status</a></code> promise needs to pay attention to what <code class=idl><a data-link-type=idl href=#dom-fontfaceset title=FontFaceSet>FontFaceSet</a></code> it’s attached to.
-	I guess only the <a data-link-type=dfn href=#font-source title="font source’s">font source’s</a> <code class=idl><a data-link-for=FontFaceSet data-link-type=idl href=#dom-fontfaceset-status title=status>status</a></code> promise should care about pending layout operations.<a href=#issue-8f48960a> ↵ </a></div></div>
+Is that always defined?<a href=#issue-0c9d1948> ↵ </a></div></div>