[css-fonts] add incremental to level 4 as well, see #6063

Author: svgeesus

css-fonts-4/Overview.bs

@@ -2025,37 +2025,63 @@ The <dfn id="at-font-face-rule">''@font-face''</dfn> rule</h3>
 
 <h4 id="font-face-src-parsing">Parsing the 'src!!descriptor' descriptor</h4>
 
+The 'src!!descriptor' descriptor value must be parsed
+according to section [[css-syntax#parse-comma-separated-list-of-component-values]].
+Then each component value is parsed according to this grammar:
 
-	The 'src!!descriptor' descriptor value must be parsed
-	according to section [[css-syntax#parse-comma-separated-list-of-component-values]].
-	Then each component value is parsed according to this grammar:
 
+<pre><<url>> [ format(<<font-format>> [supports <<font-technology>>#]?)]? | local(<<font-face-name>>)</pre>
 
-    <pre><<url>> [ format(<<font-format>> [supports <<font-technology>>#]?)]? | local(<<font-face-name>>)</pre>
+<pre class="prod"><dfn id="font-format-values">&lt;font-format&gt;</dfn>
+	 = [<<string>> | woff | truetype | opentype
+	| woff2 | embedded-opentype | collection | svg]</pre>
 
-    <pre class="prod"><dfn id="font-format-values">&lt;font-format&gt;</dfn> = [<<string>> | woff | truetype | opentype | woff2 | embedded-opentype | collection | svg]</pre>
+<pre class="prod"><dfn id="font-technology-values">&lt;font-technology&gt;</dfn>
+	 = [features(<<font-feature-technology>>) | variations
+	| color(<<color-font-technology>>) | palettes
+	| incremental ]</pre>
 
-    <pre class="prod"><dfn id="font-technology-values">&lt;font-technology&gt;</dfn>
-		= [features(<<font-feature-technology>>) | variations | color(<<color-font-technology>>) | palettes]</pre>
+<pre class="prod"><dfn id="font-feature-technology-values">&lt;font-feature-technology&gt;</dfn>
+	= [opentype | aat | graphite]</pre>
 
-	<pre class="prod"><dfn id="font-feature-technology-values">&lt;font-feature-technology&gt;</dfn>
-		= [opentype | aat | graphite]</pre>
+<pre class="prod"><dfn id="color-font-technology-values">&lt;color-font-technology&gt;</dfn>
+	= [COLRv0 | COLRv1 | SVG | sbix | CBDT ]</pre>
 
-    <pre class="prod"><dfn id="color-font-technology-values">&lt;color-font-technology&gt;</dfn>
-		= [COLRv0 | COLRv1 | SVG | sbix | CBDT ]</pre>
+If a component value is parsed correctly
+and is of a format and font technology that the UA supports,
+add it to the list of supported sources.
+If parsing a component value results in a parsing error
+or its format or technology are unsupported,
+do not add it to the list of supported sources.
 
-    If a component value is parsed correctly
-	and is of a format and font technology that the UA supports,
-	add it to the list of supported sources.
-	If parsing a component value results in a parsing error
-	or its format or technology are unsupported,
-	do not add it to the list of supported sources.
+If there are no supported entries at the end of this process,
+the value for the 'src!!descriptor' descriptor is a parse error.
 
-    If there are no supported entries at the end of this process,
-	the value for the 'src!!descriptor' descriptor is a parse error.
+These parsing rules allow for graceful fallback of fonts
+for user agents which don't support a particular font technology.
+
+<div class="example" id="ex-incremental">
+	For example,
+	when incremental transfer is not supported,
+	a woff2 compressed version of the font
+	is supplied,
+	for optimal performance.
+	Then,
+	for incremental transfer using the
+	<a href="https://www.w3.org/TR/2020/NOTE-PFE-evaluation-20201015/#range-request">range-request method</a>,
+	the raw uncompressed OpenType font is provided
+	so that the client
+	can perform byte range requests.
+
+	<pre>
+	@font-face {
+		font-family: "MyIncrementallyLoadedWebFont";
+		src: url("FallbackURLForBrowsersWhichDontSupportIncrementalLoading.woff2") format("woff2");
+		src: url("MyIncrementallyLoadedWebFont.otf") format(opentype supports incremental);
+	}
+	</pre>
+</div>
 
-    These parsing rules allow for graceful fallback of fonts
-    for user agents which don't support a particular font technology.
 
 <h4 id="font-face-src-loading">Loading an individual item in the 'src!!descriptor' descriptor</h4>
 
@@ -7209,6 +7235,7 @@ Changes
 <h3 id="changes-2021-07-29">Changes from the <a href="https://www.w3.org/TR/2021/WD-css-fonts-4-20210729/">29 July 2021 Working Draft</a> </h3>
 
 <ul>
+	<li>Added incremental font technology to supports</li>
 	<li>Reduced the critical angle for oblique font matching from 20deg to 11deg, per WG resolution</li>
 	<li>Allowed font-display in @font-feature-values (the prose allowed it but the grammar did not)</li>
 </ul>

css-fonts-5/Overview.bs

@@ -349,8 +349,7 @@ The <dfn id="at-font-face-rule">''@font-face''</dfn> rule</h3>
 
 <h4 id="font-face-src-parsing">Parsing the 'src!!descriptor' descriptor</h4>
 
-	Note: this level adds the incremental font technology.
-
+<!-- same as CSS Fonts 4, keep the two in sync -->
 
 	The 'src!!descriptor' descriptor value must be parsed
 	according to section [[css-syntax#parse-comma-separated-list-of-component-values]].