non-uniform scaling + many editorial changes

Author: davidsgrogan

css-fonts-5/Overview.bs

@@ -60,6 +60,8 @@ rules defined in CSS Fonts Level 4.
 This specification is currently a delta to the CSS Fonts Level 4 specification.
 Do not assume that if something is not here, it has been dropped.
 
+
+
 <h3 id="values">
 Value Definitions</h3>
 
@@ -74,36 +76,41 @@ also accept the <a>CSS-wide keywords</a> as their property value.
 For readability they have not been repeated explicitly.
 
 <h2 id="text-scale-meta">
-Text-Scale <code class=html>&lt;meta&gt;</code> element</h2>
+Text-Scale <{meta}> element</h2>
 
 The <dfn>text scale factor</dfn> is a multiplier
 used to calculate the computed value of the ''font-size/medium'' font size.
 The computed value of ''font-size/medium''
 is 16px
 multiplied by the [=text scale factor=].
-This factor consequently
-scales the computed size of the other <<absolute-size>> keywords.
+This factor also
+affects the computed size of the other <<absolute-size>> keywords,
+but not necessarily by the same factor as ''font-size/medium''.
+The UA should non-uniformly adjust
+keywords other than ''font-size/medium'' for improved readability.
+
+Note: Scaling all font sizes uniformly would lead to large fonts being too large.
+See <a href="https://github.com/w3c/wcag3/issues/261#issuecomment-2598860630">
+WCAG discussion about minimum and maximum critical font sizes</a>.
 
 A document with a <{meta}> tag
 whose <{meta/name}> attribute
-is a <a>ASCII case-insensitive</a> match for
-<dfn lt=text-scale><code>"text-scale"</code></dfn>
+is an <a>ASCII case-insensitive</a> match for
+<dfn lt="text-scale" export><code>"text-scale"</code></dfn>
 is recognized as controlling the [=text scale factor=].
 
-Issue(12475):
-
-The value of the <code>content</code>
+The value of the <{meta/content}>
 attribute must be an <a>ASCII case-insensitive</a> match for one of the
 recognized keywords. Otherwise the tag is ignored.
 
 Documents without this <{meta}> tag will have an assumed default
-value of <code>legacy</code>.
+value of <a for="text-scale">legacy</a>.
 
 <div class="example" id="ex-text-scale">
-	<pre>&lt;meta name="text-scale" content="scale" /></pre>
+	<pre class="lang-html">&lt;meta name="text-scale" content="scale" /></pre>
 </div>
 
-There must not be more than one <{meta}> element with its <{meta/name}> attribute value set to an [=ASCII case-insensitive=] for [=text-scale=] per document.
+There must not be more than one <{meta}> element with its <{meta/name}> attribute value set to an [=ASCII case-insensitive=] match for [=text-scale=] per document.
 
 <h3 id="text-scale-meta-keywords">
 Keywords</h3>
@@ -113,49 +120,47 @@ The recognized keywords in the [=text-scale=]
 
 <dl>
 	<dt><dfn for="text-scale">legacy</dfn></dt>
-	<dd>The ''env()/preferred-text-scale'' environment variable returns the user's OS-level font factor on mobile,
-	but 1 on desktop.
-	The document's ''font-size/medium'' font size incorporates UA-level font preferences.
-	OS-level font preferences are ignored.
+	<dd>
+		The ''env()/preferred-text-scale'' environment variable returns the user's OS-level font factor on mobile devices,
+		but 1 on desktop devices.
+		[=text scale factor=] incorporates UA-level font preferences but
+		OS-level font preferences are ignored.
 
-	Note: Equivalent to omitting a [=text-scale=] <{meta}> tag or
-	including an unrecognized content attribute keyword.
+		Note: Equivalent to omitting a [=text-scale=] <{meta}> tag or
+		including an unrecognized content attribute keyword.
+	</dd>
+	<dt><dfn for="text-scale">scale</dfn></dt>
+	<dd>
+		The ''env()/preferred-text-scale'' environment variable returns the user's OS-level font preferences.
+		[=text scale factor=] incorporates both UA-level and OS-level font preferences.
 	</dd>
-	<dt><dfn>scale</dfn></dt>
-	<dd>The ''env()/preferred-text-scale'' environment variable returns the user's OS-level font preferences.
-	The document's ''font-size/medium'' font size incorporates both UA-level and OS-level font preferences.</dd>
 </dl>
 
-<h3 id="legacy-keyword">The 'legacy' keyword</h3>
+<h3 id="legacy-keyword">The <a for="text-scale">legacy</a> keyword</h3>
 
 When the value of the [=text-scale=] content attribute is
 [=text-scale/legacy=],
 the [=text scale factor=] is the font scale factor
-the user has chosen from any settings <i>provided by the user agent</i>.
-The ''preferred-text-scale'' environment variable value must be 1 on desktop platforms.
-On mobile:
-<ul>
-	<li>if the operating system provides a text scale setting AND
-	the UA hasn't already applied that factor to the ''font-size/medium'' font size,
-	the ''env()/preferred-text-scale'' environment variable returns the multiplier
-	that the user has chosen in the operating system's text scale setting.
+the user has chosen from any settings provided <i>only</i> by the user agent.
+The ''env()/preferred-text-scale'' environment variable value must be 1 on desktop platforms.
 
-	Note: At the time of publishing, all combinations of
-	Android, iOS,
-	Firefox, Safari, Chrome
-	satisfy this first condition.
+On mobile platforms:
+<ul>
+	<li>
+		If the operating system provides a text scale setting AND
+		the UA hasn't already applied that factor to the ''font-size/medium'' font size,
+		the ''env()/preferred-text-scale'' environment variable returns the multiplier
+		that the user has chosen in the operating system's text scale setting.
 
+		Note: At the time of publishing, all combinations of Android, iOS, Firefox, Safari, and Chrome satisfy this first condition.
 	</li>
 	<li>Otherwise the ''env()/preferred-text-scale'' environment variable returns 1.</li>
 </ul>
 
 <h3 id="scale-keyword">The 'scale' keyword</h3>
 
-The <dfn for="text-scale" export><code>scale</code></dfn> property is
-recognized in the [=text-scale=] content attribute value.
-
 When the value of the [=text-scale=] content attribute is
-<a for=text-scale>scale</a>,
+<a for="text-scale">scale</a>,
 the [=text scale factor=] matches the user's preferred paragraph text size
 (as determined from a combination of OS and UA preferences)
 divided by 16px.
@@ -165,34 +170,36 @@ The ''env()/preferred-text-scale'' environment variable must return the [=text s
 Further, when the value of the [=text-scale=] content attribute is
 <a for=text-scale>scale</a>, the user agent should skip all font-sizing interventions it would otherwise perform in an attempt to automatically honor the user's preferences. E.g. text autosizing on mobile (See [[css-size-adjust#intro]]) and full-application zoom (<a href="https://github.com/w3c/csswg-drafts/blob/main/css-env-1/explainers/env-preferred-text-scale.md#windows-11">popular browsers do this on Windows)</a>.
 
-Note: Authors are expected to use
-''&lt;meta name="text-scale" content="scale"&gt;'' in stylesheets so that the ''font-size/medium'' font size will reflect a combination of the user's font preferences, whether those are specified at the OS level or the UA level. The author will then be able to use ''rem'' throughout the page to honor the user's font preferences.
+Note:
+Authors are expected to use
+<code>&lt;meta name="text-scale" content="scale"&gt;</code> in stylesheets so that the ''font-size/medium'' font size will reflect a combination of the user's font preferences, whether those are specified at the OS level or the UA level. The author will then be able to use ''rem'' throughout the page to honor the user's font preferences.
 
 <div class="example" id="ex-scaled-page">
 	If authors don't alter the '':root'' font size, content sized with ''rem'' units will be relative to the preferred text scale
-	<pre>
+	<pre class="lang-html">
 &lt;!DOCTYPE html>
 &lt;html> &lt;!-- leave this element's font-size as the default -->
 	&lt;head>
 		&lt;meta name="text-scale" content="scale" />
 	&lt;/head>
 	&lt;body>
 		&lt;div style="font-size: 1rem;">
-		  This font size obeys the user's font preferences, **whether
+			This font size obeys the user's font preferences, **whether
 			those preferences are specified at the operating system level
 			or the user agent level**
 		&lt;/div>
 		&lt;div style="font-size: 20px;">
-		  This font size does NOT respect the user's font preferences.
+			This font size does NOT respect the user's font preferences.
 			&lt;div style="font-size: 1rem;">
-			  But this font size does!
+				But this font size does!
 			&lt;/div>
 		&lt;/div>
 	&lt;/body>
 &lt;/html>
 	</pre>
 </div>
 
+
 <h2 id="basic-font-props">
 Basic Font Properties</h2>