[css-values-4][mediaqueries-5] Clarify when minimum font sizes/etc are or aren't applied to relative units. Fixes w3c#5858.

tabatkins · tabatkins · commit 0f0f29753a6f · 2021-02-02T10:26:11.000-08:00
diff --git a/css-values-4/Overview.bs b/css-values-4/Overview.bs
@@ -1671,10 +1671,20 @@ Font-relative Lengths: the ''em'', ''ex'', ''cap'', ''ch'', ''ic'', ''rem'', ''l
 	that it would be worth adding them?
 	Or should we just wait for Houdini Custom Units?
 
+	Some user-agents allow users to apply additional restrictions to font sizes in a document,
+	such as setting minimum font sizes to ensure readability.
+	When used in the context of an element,
+	these additional restrictions must be applied to the [=used value=] of these properties only;
+	they <em>must not</em> affect the resolution of relative units.
+
 	When used outside the context of an element
 	(such as in <a>media queries</a>),
 	these units refer to the metrics corresponding
 	to the initial values of the 'font' and 'line-height' properties.
+	In this context,
+	the units must apply any additional restrictions to the values,
+	contrary to the normal behavior mentioned above.
+
 	When used in the value of the 'font-size' property on the element they refer to,
 	they resolve against the computed metrics of the parent element--
 	or against the computed metrics corresponding to the initial values
@@ -1690,6 +1700,7 @@ Font-relative Lengths: the ''em'', ''ex'', ''cap'', ''ch'', ''ic'', ''rem'', ''l
 	(The other font-relative units continue to resolve against
 	the element’s own metrics when used in 'line-height'.)
 
+
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diff --git a/mediaqueries-5/Overview.bs b/mediaqueries-5/Overview.bs
@@ -25,11 +25,15 @@ At Risk: The '@media/update' media feature
 
 <pre class=link-defaults>
 spec:css-conditional-3; type:at-rule; text:@media
-spec:css-values-4; type:type; text:<ratio>
-spec:css-values-4; type:type; text:<integer>
-spec:css-values-4; type:type; text:<length>
-spec:css-values-4; type:type; text:<number>
-spec:css-values-4; type:type; text:<resolution>
+spec:css-values-4;
+	type:type;
+		text:<ratio>
+		text:<length>
+		text:<integer>
+		text:<number>
+		text:<resolution>
+	type:dfn; text:relative length
+
 </pre>
 
 <pre class=biblio>
@@ -135,11 +139,15 @@ Units</h3>
 	defined in [[!CSS-VALUES-4]]. For example, the pixel unit represents CSS pixels and
 	not physical pixels.
 
-	<a spec="css-values">Relative length</a> units in media queries are based on the <a>initial value</a>, which means
-	that units are never based on results of declarations. <span class=note>For example, in HTML,
+	[=Relative length=] units in media queries are based on the <a>initial value</a>,
+	which means that units are never based on results of declarations.
+
+	Note: For example, in HTML,
 	the ''em'' unit is relative to the <a>initial value</a> of 'font-size',
 	defined by the user agent or the user's preferences,
-	not any styling on the page.</span>
+	not any styling on the page.
+	Note that this will also take into account additional restrictions the user might apply,
+	such as minimum font sizes.
 
 <h3 id='mq-prefers-security'>
 Prefers-* Media Features Security and Privacy</h3>
@@ -2160,13 +2168,13 @@ All Available Interaction Capabilities: the 'any-pointer' and 'any-hover' featur
 	</div>
 
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 <h2 id="video-prefixed-features">Video Prefixed Features</h2>
