Fixed daily activity graph bug related to DST management.

locallib.php

@@ -961,8 +961,8 @@ function vpl_get_webservice_urlbase($vpl) {
            . '&wstoken=' . $token . '&id=' . $vpl->get_course_module()->id . '&wsfunction=';
 }
 
-function vpl_timestamp_to_midnight($timestamp) {
-    return $timestamp - ($timestamp + date('Z')) % 86400;
+function vpl_timestamp_to_midday($timestamp) {
+    return $timestamp - ($timestamp + date('Z')) % 86400 + 43200;
 }
 
 function vpl_get_name_fields_display() {

views/vpl_grapher.class.php

@@ -337,7 +337,7 @@ class vpl_grapher {
                 $start = min($start, $subinstance->datesubmitted);
             }
         }
-        $start = vpl_timestamp_to_midnight($start);
+        $start = vpl_timestamp_to_midday($start);
 
         // End of time span is either module due date, either last submission date.
         if ($this->vpl->get_instance()->duedate > 0) {
@@ -348,7 +348,7 @@ class vpl_grapher {
                 $end = max($end, $subinstance->datesubmitted);
             }
         }
-        $end = vpl_timestamp_to_midnight($end);
+        $end = vpl_timestamp_to_midday($end);
 
         // Compute per-day activity (ie. number of submissions).
         $days = array();
@@ -359,8 +359,11 @@ class vpl_grapher {
         }
 
         foreach ($this->submissions as $subinstance) {
-            $daysubmitted = vpl_timestamp_to_midnight($subinstance->datesubmitted);
-            $dailyactivity[($daysubmitted - $start) / 86400] ++;
+            $daysubmitted = vpl_timestamp_to_midday($subinstance->datesubmitted);
+            $dayoffset = ($daysubmitted - $start) / 86400;
+            if (isset($dailyactivity[$dayoffset])) {
+                $dailyactivity[$dayoffset] ++;
+            }
         }
 
         // Draw the graph.