Add explanation of open issue on the automatic reversing algorithm.

Author: dbaron

css3-transitions/Overview.html

@@ -29,14 +29,14 @@
 
    <h1>CSS Transitions</h1>
 
-   <h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 21 March 2011</h2>
+   <h2 class="no-num no-toc" id=longstatus-date>Editor's Draft 26 March 2011</h2>
 
    <dl>
     <dt>This version:
 
-    <dd> <a href="http://www.w3.org/TR/2011/ED-css3-transitions-20110321">
+    <dd> <a href="http://www.w3.org/TR/2011/ED-css3-transitions-20110326">
      http://dev.w3.org/csswg/css3-transitions/</a>
-     <!--http://www.w3.org/TR/2011/WD-css3-transitions-20110321-->
+     <!--http://www.w3.org/TR/2011/WD-css3-transitions-20110326-->
 
     <dt>Latest version:
 
@@ -873,6 +873,25 @@ <h2 id=reversing><span class=secno>4. </span> Automatically reversing
    for example, if the transition reversing to state A was again interrupted
    by a property change to state B.
 
+  <p class=issue>Issue: This introduces the concept of reversing a timing
+   function, which the spec has otherwise resisted doing, and also introduces
+   a discontinuity between transitions that have almost completed (which get
+   automatically reversed and thus have their timing function reversed) and
+   transitions that have fully completed (where the reversal doesn't lead to
+   the timing function being reversed). An alternative proposal that avoids
+   this is to follow the normal timing function algorithm, except multiply
+   the duration (and also shorten any negative delay) by the (output) value
+   of the transition timing function of the incomplete transition at the time
+   it was interrupted, and, to account for multiple reverses in sequence, to
+   divide by the shortening applied to the transition being interrupted. For
+   more details see this thread: <a
+   href="http://lists.w3.org/Archives/Public/www-style/2009Nov/thread.html#msg302">November
+   2009 part</a>, <a
+   href="http://lists.w3.org/Archives/Public/www-style/2009Dec/thread.html#msg319">December
+   2009 part</a>, <a
+   href="http://lists.w3.org/Archives/Public/www-style/2010Jan/thread.html#msg136">January
+   2010 part</a>.
+
   <h2 id=transition-events-><span class=secno>5. </span> Transition Events</h2>
 
   <p> The completion of a CSS Transition generates a corresponding <a

css3-transitions/Overview.src.html

@@ -835,6 +835,26 @@ <h2 id="reversing">
         again interrupted by a property change to state B.
       </p>
 
+      <p class="issue">Issue:
+        This introduces the concept of reversing a timing function,
+        which the spec has otherwise resisted doing, and also introduces
+        a discontinuity between transitions that have
+        almost completed (which get automatically reversed and thus have
+        their timing function reversed) and transitions that have fully
+        completed (where the reversal doesn't lead to the timing
+        function being reversed).  An alternative proposal that avoids
+        this is to follow the normal timing function algorithm, except
+        multiply the duration (and also shorten any negative delay) by
+        the (output) value of the transition timing function of the
+        incomplete transition at the time it was interrupted, and, to
+        account for multiple reverses in sequence, to divide by the
+        shortening applied to the transition being interrupted.  For
+        more details see this thread:
+        <a href="http://lists.w3.org/Archives/Public/www-style/2009Nov/thread.html#msg302">November 2009 part</a>,
+        <a href="http://lists.w3.org/Archives/Public/www-style/2009Dec/thread.html#msg319">December 2009 part</a>,
+        <a href="http://lists.w3.org/Archives/Public/www-style/2010Jan/thread.html#msg136">January 2010 part</a>.
+      </p>
+
       <h2>
         Transition Events
       </h2>