[css-shapes] switch from SVG to CSS behavior for solving bad rounded corner radii

Author: astearns

css-shapes/Overview.html

@@ -367,14 +367,7 @@ <h4 id=supported-basic-shapes><span class=secno>3.2.1. </span>Supported
       <strong> rx</strong> and <strong>ry</strong>. For rounded rectangles
       they define the x-axis radius and y-axis radius of the ellipse used to
       round off the corners of the rectangle. Negative values for rx and ry
-      are invalid. Implicit values may apply if one or the other of these
-      values are unspecified or invalid, and clamping may occur if a
-      specified value would result in a negative straight rectangle segment.
-      The corner radii rules in <a
-      href="http://www.w3.org/TR/SVG/shapes.html#RectElement">the ‘<code
-      class=property>rect</code>’ element</a> in the SVG recommendation
-      define these edge cases <a href="#SVG11"
-      rel=biblioentry>[SVG11]<!--{{!SVG11}}--></a>.
+      are invalid. See notes below on edge cases for these values.
     </ul>
 
    <dt><dfn
@@ -391,14 +384,8 @@ <h4 id=supported-basic-shapes><span class=secno>3.2.1. </span>Supported
       <strong> rx</strong> and <strong>ry</strong>. For rounded inset
       rectangles they define the x-axis radius and y-axis radius of the
       ellipse used to round off the corners of the inset rectangle. Negative
-      values for rx and ry are invalid. Implicit values may apply if one or
-      the other of these values are unspecified or invalid, and clamping may
-      occur if a specified value would result in a negative straight
-      rectangle segment. The corner radii rules in <a
-      href="http://www.w3.org/TR/SVG/shapes.html#RectElement">the ‘<code
-      class=property>rect</code>’ element</a> in the SVG recommendation
-      define these edge cases <a href="#SVG11"
-      rel=biblioentry>[SVG11]<!--{{!SVG11}}--></a>.
+      values for rx and ry are invalid. See notes below on edge cases for
+      these values.
     </ul>
 
    <dt><dfn id=circle>circle</dfn>([&lt;length&gt;|&lt;percentage&gt;]{3})
@@ -442,7 +429,19 @@ <h4 id=supported-basic-shapes><span class=secno>3.2.1. </span>Supported
      first vertex of the list.</p>
     <br>
   </dl>
-  <!--
+
+  <p>The values for corner radii on rectangle or inset-rectangle are
+   determined implicitly if either the rx or ry values are not specified, or
+   are specified but with invalid values. If neither rx nor ry are properly
+   specified, the values are 0 for both. If only one value is properly
+   specified, that value is used for both. And if the values cause any of the
+   curves to overlap, the solution for <a
+   href="http://www.w3.org/TR/css3-background/#corner-overlap">overlapping
+   curves</a> from CSS Backgrounds and Borders <a href="#CSS3BG"
+   rel=biblioentry>[CSS3BG]<!--{{!CSS3BG}}--></a> is used to avoid the
+   overlap.
+
+  <p> <!--
 <div class="issue-marker wrapper">
     <div class="issue-marker" data-bug_id="16448" data-bug_status="ASSIGNED">
       <a href="https://www.w3.org/Bugs/Public/show_bug.cgi?id=16448">Issue-16448</a>
@@ -512,7 +511,7 @@ <h4 id='referencing-svg-shapes'>Referencing SVG shapes</h4>
         </p>
 
 -->
-  <!-- End section "Shapes from SVG Syntax -->
+   <!-- End section "Shapes from SVG Syntax -->
 
   <h4 id=basic-shape-interpolation><span class=secno>3.2.2.
    </span>Interpolation of Basic Shapes</h4>
@@ -1034,6 +1033,16 @@ <h3 class=no-num id=normative-references>Normative references</h3>
    </dd>
    <!---->
 
+   <dt id=CSS3BG>[CSS3BG]
+
+   <dd>Bert Bos; Elika J. Etemad; Brad Kemper. <a
+    href="http://www.w3.org/TR/2012/CR-css3-background-20120724/"><cite>CSS
+    Backgrounds and Borders Module Level 3.</cite></a> 24 July 2012. W3C
+    Candidate Recommendation. (Work in progress.) URL: <a
+    href="http://www.w3.org/TR/2012/CR-css3-background-20120724/">http://www.w3.org/TR/2012/CR-css3-background-20120724/</a>
+   </dd>
+   <!---->
+
    <dt id=CSS3BOX>[CSS3BOX]
 
    <dd>Bert Bos. <a

css-shapes/Overview.src.html

@@ -248,12 +248,7 @@ <h4 id="supported-basic-shapes">Supported Shapes</h4>
                       of the ellipse used to round off 
                       the corners of the rectangle. 
                       Negative values for rx and ry are invalid. 
-                      Implicit values may apply if one or the other 
-                      of these values are unspecified or invalid, 
-                      and clamping may occur if a specified value 
-                      would result in a negative straight rectangle segment. 
-                      The corner radii rules in <a href="http://www.w3.org/TR/SVG/shapes.html#RectElement">the 'rect' element</a> 
-                      in the SVG recommendation define these edge cases [[!SVG11]].
+                      See notes below on edge cases for these values.
                   </li>
               </ul>
           </dd>
@@ -275,13 +270,8 @@ <h4 id="supported-basic-shapes">Supported Shapes</h4>
                       the x-axis radius and y-axis radius 
                       of the ellipse used to round off 
                       the corners of the inset rectangle. 
-                      Negative values for rx and ry are invalid.
-                      Implicit values may apply if one or the other 
-                      of these values are unspecified or invalid, 
-                      and clamping may occur if a specified value 
-                      would result in a negative straight rectangle segment. 
-                      The corner radii rules in <a href="http://www.w3.org/TR/SVG/shapes.html#RectElement">the 'rect' element</a> 
-                      in the SVG recommendation define these edge cases [[!SVG11]].
+                      Negative values for rx and ry are invalid. 
+                      See notes below on edge cases for these values.
                   </li>
               </ul>
           </dd>
@@ -334,6 +324,24 @@ <h4 id="supported-basic-shapes">Supported Shapes</h4>
               <br/>
           </dd>
       </dl>
+
+      <p>The values for corner radii 
+        on rectangle or inset-rectangle 
+        are determined implicitly 
+        if either the rx or ry values 
+        are not specified, 
+        or are specified but with invalid values. 
+        If neither rx nor ry are properly specified, 
+        the values are 0 for both. 
+        If only one value is properly specified, 
+        that value is used for both. 
+        And if the values cause any 
+        of the curves to overlap, 
+        the solution for 
+        <a href="http://www.w3.org/TR/css3-background/#corner-overlap">overlapping curves</a> 
+        from CSS Backgrounds and Borders [[!CSS3BG]] 
+        is used to avoid the overlap.
+      <p>
 <!--
 <div class="issue-marker wrapper">
     <div class="issue-marker" data-bug_id="16448" data-bug_status="ASSIGNED">