From 0b2e8ae07b7cd4e0b62e7542146144d5bf9513ef Mon Sep 17 00:00:00 2001
From: Frederic Massart <fred@moodle.com>
Date: Fri, 26 Sep 2014 17:32:08 +0800
Subject: [PATCH] MDL-47430 core_grades: Handle negative grademin with natural
 weighting

Part of: MDL-46576
---
 grade/report/user/lib.php    | 11 +++++++++--
 lib/grade/grade_category.php | 31 +++++++++++++++++++++++++------
 2 files changed, 34 insertions(+), 8 deletions(-)

diff --git a/grade/report/user/lib.php b/grade/report/user/lib.php
index fad11d7b2be..8bba9233376 100644
--- a/grade/report/user/lib.php
+++ b/grade/report/user/lib.php
@@ -706,8 +706,15 @@ class grade_report_user extends grade_report {
             if (isset($this->aggregationhints[$itemid])) {
 
                 // Normalise the gradeval.
-                $graderange = $this->aggregationhints[$itemid]['grademax'] - $this->aggregationhints[$itemid]['grademin'];
-                $gradeval = ($this->aggregationhints[$itemid]['grade'] - $this->aggregationhints[$itemid]['grademin']) / $graderange;
+                $gradecat = $grade_object->load_parent_category();
+                if ($gradecat->aggregation == GRADE_AGGREGATE_SUM) {
+                    // Natural aggregation/Sum of grades does not consider the mingrade.
+                    $graderange = $this->aggregationhints[$itemid]['grademax'];
+                    $gradeval = $this->aggregationhints[$itemid]['grade'] / $graderange;
+                } else {
+                    $graderange = $this->aggregationhints[$itemid]['grademax'] - $this->aggregationhints[$itemid]['grademin'];
+                    $gradeval = ($this->aggregationhints[$itemid]['grade'] - $this->aggregationhints[$itemid]['grademin']) / $graderange;
+                }
 
                 // Multiply the normalised value by the weight
                 // of all the categories higher in the tree.
diff --git a/lib/grade/grade_category.php b/lib/grade/grade_category.php
index 8eb0f6abb4f..f26f8212d01 100644
--- a/lib/grade/grade_category.php
+++ b/lib/grade/grade_category.php
@@ -661,7 +661,13 @@ class grade_category extends grade_object {
             if (isset($grademaxoverrides[$itemid])) {
                 $usergrademax = $grademaxoverrides[$itemid];
             }
-            $grade_values[$itemid] = grade_grade::standardise_score($v, $usergrademin, $usergrademax, 0, 1);
+            if ($this->aggregation == GRADE_AGGREGATE_SUM) {
+                // Assume that the grademin is 0 when standardising the score, to preserve negative grades.
+                $grade_values[$itemid] = grade_grade::standardise_score($v, 0, $usergrademax, 0, 1);
+            } else {
+                $grade_values[$itemid] = grade_grade::standardise_score($v, $usergrademin, $usergrademax, 0, 1);
+            }
+
         }
 
         // For items with no value, and not excluded - either set their grade to 0 or exclude them.
@@ -715,16 +721,29 @@ class grade_category extends grade_object {
                                                             $grademaxoverrides);
         $agg_grade = $result['grade'];
 
+        // Set the actual grademin and max to bind the grade properly.
+        $this->grade_item->grademin = $result['grademin'];
+        $this->grade_item->grademax = $result['grademax'];
+
+        if ($this->aggregation == GRADE_AGGREGATE_SUM) {
+            // The natural aggregation always displays the range as coming from 0 for categories.
+            // However, when we bind the grade we allow for negative values.
+            $result['grademin'] = 0;
+        }
+
         // Recalculate the grade back to requested range.
         $finalgrade = grade_grade::standardise_score($agg_grade, 0, 1, $result['grademin'], $result['grademax']);
-
         $grade->finalgrade = $this->grade_item->bounded_grade($finalgrade);
+
+        $oldrawgrademin = $grade->rawgrademin;
         $oldrawgrademax = $grade->rawgrademax;
+        $grade->rawgrademin = $result['grademin'];
         $grade->rawgrademax = $result['grademax'];
 
-        // update in db if changed
+        // Update in db if changed.
         if (grade_floats_different($grade->finalgrade, $oldfinalgrade) ||
-            grade_floats_different($grade->rawgrademax, $oldrawgrademax)) {
+                grade_floats_different($grade->rawgrademax, $oldrawgrademax) ||
+                grade_floats_different($grade->rawgrademin, $oldrawgrademin)) {
             $grade->update('aggregation');
         }
 
@@ -1046,11 +1065,11 @@ class grade_category extends grade_object {
                     if (isset($grademaxoverrides[$itemid])) {
                         $usergrademax = $grademaxoverrides[$itemid];
                     }
-                    $gradeitemrange = $usergrademax - $usergrademin;
 
                     // Ignore extra credit and items with a weight of 0.
                     if ($items[$itemid]->aggregationcoef <= 0 && $items[$itemid]->aggregationcoef2 > 0) {
-                        $grademax += $gradeitemrange;
+                        $grademin += $usergrademin;
+                        $grademax += $usergrademax;
                         $sumweights += $items[$itemid]->aggregationcoef2;
                     }
                 }