[geometry-1] Define minimum and maximum as preferring NaN

Fixes w3c#222.

geometry/Overview.bs

@@ -368,17 +368,21 @@ for=rectangle>height dimension</a> value. For the {{DOMRect}} interface, setting
 {{DOMRect/height}} attribute must set the <a for=rectangle>height dimension</a> value to the new
 value.
 
-The <dfn><code>top</code></dfn> attribute, on getting, must return min(<a for=rectangle>y
-coordinate</a>, <a for=rectangle>y coordinate</a> + <a for=rectangle>height dimension</a>).
+The <dfn><code>top</code></dfn> attribute, on getting, must return the <a>NaN-safe minimum</a> of
+the <a for=rectangle>y coordinate</a> and the sum of the <a for=rectangle>y coordinate</a> and the
+<a for=rectangle>height dimension</a>.
 
-The <dfn><code>right</code></dfn> attribute, on getting, must return max(<a for=rectangle>x
-coordinate</a>, <a for=rectangle>x coordinate</a> + <a for=rectangle>width dimension</a>).
+The <dfn><code>right</code></dfn> attribute, on getting, must return the <a>NaN-safe maximum</a> of
+the <a for=rectangle>x coordinate</a> and the sum of the <a for=rectangle>x coordinate</a> and the
+<a for=rectangle>width dimension</a>.
 
-The <dfn><code>bottom</code></dfn> attribute, on getting, must return max(<a for=rectangle>y
-coordinate</a>, <a for=rectangle>y coordinate</a> + <a for=rectangle>height dimension</a>).
+The <dfn><code>bottom</code></dfn> attribute, on getting, must return the <a>NaN-safe maximum</a>
+of the <a for=rectangle>y coordinate</a> and the sum of the <a for=rectangle>y coordinate</a> and
+the <a for=rectangle>height dimension</a>.
 
-The <dfn><code>left</code></dfn> attribute, on getting, must return min(<a for=rectangle>x
-coordinate</a>, <a for=rectangle>x coordinate</a> + <a for=rectangle>width dimension</a>).
+The <dfn><code>left</code></dfn> attribute, on getting, must return the <a>NaN-safe minimum</a> of
+the <a for=rectangle>x coordinate</a> and the sum of the <a for=rectangle>x coordinate</a> and the
+<a for=rectangle>width dimension</a>.
 </div>
 
 
@@ -528,21 +532,21 @@ The <dfn method for=DOMQuad>getBounds()</dfn> method, when invoked, must run the
 algorithm:
 
 1. Let <var>bounds</var> be a {{DOMRect}} object.
-2. Let <var>left</var> be the minimum of <a for=quadrilateral>point 1</a>'s <a for=point>x
-    coordinate</a>, <a for=quadrilateral>point 2</a>'s <a for=point>x coordinate</a>, <a
-    for=quadrilateral>point 3</a>'s <a for=point>x coordinate</a> and <a for=quadrilateral>point
+2. Let <var>left</var> be the <a>NaN-safe minimum</a> of <a for=quadrilateral>point 1</a>'s <a
+    for=point>x coordinate</a>, <a for=quadrilateral>point 2</a>'s <a for=point>x coordinate</a>,
+    <a for=quadrilateral>point 3</a>'s <a for=point>x coordinate</a> and <a for=quadrilateral>point
     4</a>'s <a for=point>x coordinate</a>.
-3. Let <var>top</var> be the minimum of <a for=quadrilateral>point 1</a>'s <a for=point>y
-    coordinate</a>, <a for=quadrilateral>point 2</a>'s <a for=point>y coordinate</a>, <a
-    for=quadrilateral>point 3</a>'s <a for=point>y coordinate</a> and <a for=quadrilateral>point
+3. Let <var>top</var> be the <a>NaN-safe minimum</a> of <a for=quadrilateral>point 1</a>'s <a
+    for=point>y coordinate</a>, <a for=quadrilateral>point 2</a>'s <a for=point>y coordinate</a>,
+    <a for=quadrilateral>point 3</a>'s <a for=point>y coordinate</a> and <a for=quadrilateral>point
     4</a>'s <a for=point>y coordinate</a>.
-4. Let <var>right</var> be the maximum of <a for=quadrilateral>point 1</a>'s <a for=point>x
-    coordinate</a>, <a for=quadrilateral>point 2</a>'s <a for=point>x coordinate</a>, <a
-    for=quadrilateral>point 3</a>'s <a for=point>x coordinate</a> and <a for=quadrilateral>point
+4. Let <var>right</var> be the <a>NaN-safe maximum</a> of <a for=quadrilateral>point 1</a>'s <a
+    for=point>x coordinate</a>, <a for=quadrilateral>point 2</a>'s <a for=point>x coordinate</a>,
+    <a for=quadrilateral>point 3</a>'s <a for=point>x coordinate</a> and <a for=quadrilateral>point
     4</a>'s <a for=point>x coordinate</a>.
-5. Let <var>bottom</var> be the maximum of <a for=quadrilateral>point 1</a>'s <a for=point>y
-    coordinate</a>, <a for=quadrilateral>point 2</a>'s <a for=point>y coordinate</a>, <a
-    for=quadrilateral>point 3</a>'s <a for=point>y coordinate</a> and <a for=quadrilateral>point
+5. Let <var>bottom</var> be the <a>NaN-safe maximum</a> of <a for=quadrilateral>point 1</a>'s <a
+    for=point>y coordinate</a>, <a for=quadrilateral>point 2</a>'s <a for=point>y coordinate</a>,
+    <a for=quadrilateral>point 3</a>'s <a for=point>y coordinate</a> and <a for=quadrilateral>point
     4</a>'s <a for=point>y coordinate</a>.
 6. Set <a for=rectangle>x coordinate</a> of <var>bounds</var> to <var>left</var>, <a
     for=rectangle>y coordinate</a> of <var>bounds</var> to <var>top</var>, <a for=rectangle>width
@@ -1787,6 +1791,13 @@ Web. It is defined in this specification as an alias to {{DOMMatrix}}.
 Some user agents supported a <code>MSCSSMatrix</code> interface. Implementations conforming to
 this specification will not support <code>MSCSSMatrix</code>.
 
+<h2 class="no-num" id="conventions">Document conventions</h2>
+
+The <dfn>NaN-safe minimum</dfn> of a non-empty list of {{unrestricted double}} values is NaN if any
+member of the list is NaN, or the minimum of the list otherwise.
+
+Analogously, the <dfn>NaN-safe maximum</dfn> of a non-empty list of {{unrestricted double}} values
+is NaN if any member of the list is NaN, or the maximum of the list otherwise.
 
 <h2 class="no-num" id="changes">Changes since last publication</h2>