--- loncom/interface/lonhtmlcommon.pm	2012/03/25 14:36:01	1.304
+++ loncom/interface/lonhtmlcommon.pm	2012/04/04 10:47:29	1.307
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA
 # a pile of common html routines
 #
-# $Id: lonhtmlcommon.pm,v 1.304 2012/03/25 14:36:01 foxr Exp $
+# $Id: lonhtmlcommon.pm,v 1.307 2012/04/04 10:47:29 foxr Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -1309,21 +1309,55 @@ sub htmlareaselectactive {
                 $.fn.jPicker.defaults.images.clientPath="/adm/jpicker/images/";
                 $(".colorchooser").jPicker();
 
-                // Only define the countdown if a dueDate variable is defined:
-
-               if (typeof(dueDate) != "undefined") {
-                  $("#duedatecountdown").countdown({until: dueDate, compact: true, 
-                                                  layout: "<b>Due in: {dn} {dl} {hnn}{sep}{mnn}{sep}{snn}</b>",
-                                                  onTick: function (periods) {
-                         if($.countdown.periodsToSeconds(periods) < 60) {
-                             $(this).css("color", "red");   //Highlight last minute.
-                         }
-                      }
-                  });
-               }
 
 	});
 ';
+    # Code to put a due date countdown in 'duedatecountdown' span.
+    # This is currently located in the breadcrumb headers.
+    # note that the dueDateLayout is internatinoalized below.
+    # Here document is used to support the substitution into the javascript below.
+    # ..which unforunately necessitates escaping the $'s in the javascript.
+    # There are several times of importance
+    #
+    # serverDueDate -  The absolute time at which the problem expires.
+    # serverTime    -  The server's time when the problem finished computing.
+    # clientTime    -  The client's time...as close to serverTime as possible.
+    #                  The clientTime will be slightly later due to
+    #                  1. The latency between problem computation and 
+    #                     the first network action.
+    #                  2. The time required between the page load-start and the actual
+    #                     initial javascript execution that got clientTime.
+    # These are used as follows:
+    #   The difference between clientTime and serverTime are used to 
+    #   correct for differences in clock settings between the browser's system and the
+    #   server's.
+    #
+    #   The difference between clientTime and the time at which the ready() method
+    #   starts executing is used to estimate latencies for page load and submission.
+    #   Since this is an estimate, it is doubled.  The latency estimate + one minute
+    #   is used to determine when the countdown timer turns red to warn the user
+    #   to think about submitting.
+
+    my $dueDateLayout = '<b>' .  &mt('Due in: {dn} {dl} {hnn}{sep}{mnn}{sep}{snn} - Submit early!') . '</b>';
+    $output .= <<JAVASCRIPT;
+
+    var documentReadyTime;
+
+\$(document).ready(function() {
+   if (typeof(dueDate) != "undefined") {
+       documentReadyTime = (new Date()).getTime();
+      \$("#duedatecountdown").countdown({until: dueDate, compact: true, 
+         layout: "$dueDateLayout",
+         onTick: function (periods) {
+	    var latencyEstimate = (documentReadyTime - clientTime) * 2;
+            if(\$.countdown.periodsToSeconds(periods) < (60 + latencyEstimate)) {
+               \$(this).css("color", "red");   //Highlight last minute.
+            }
+         }
+      });
+   }
+});
+JAVASCRIPT
     if ($dragmath_prefix ne '') {
         $output .= '
 
@@ -1430,6 +1464,29 @@ var dueDate       = new Date(serverDueDa
 </script>
 ";
 
+    return $js;
+}
+##
+# Sets the time at which the problem finished computing.
+# This just updates the serverTime and clientTime variables above.
+# Calling this in e.g. end_problem provides a better estimate of the
+# difference beetween the server and client time setting as 
+# the difference contains less of the latency/problem compute time.
+#
+sub set_compute_end_time {
+
+    my $now = time()*1000;	# Javascript times are in ms.
+    my $js = "
+<script type='text/javascript'>
+//<![CDATA[
+serverTime = $now;
+clientTime = (new Date()).getTime();
+//]]>
+</script>
+
+";
+    return $js;
+    
 }
 
 ############################################################