MDL-55030 core: Bar charts defaults to using a Y axis starting at 0

Part of MDL-54987 epic.

lib/amd/build/chart_bar.min.js

@@ -1 +1 @@
-define(["core/chart_base"],function(a){function b(){a.prototype.constructor.apply(this,arguments)}return b.prototype=Object.create(a.prototype),b.prototype.TYPE="bar",b});
+define(["core/chart_base"],function(a){function b(){a.prototype.constructor.apply(this,arguments)}return b.prototype=Object.create(a.prototype),b.prototype.TYPE="bar",b.prototype._setDefaults=function(){a.prototype._setDefaults.apply(this,arguments);var b=this.getYAxis(0,!0);b.setMin(0)},b});

lib/amd/src/chart_bar.js

@@ -32,6 +32,12 @@ define(['core/chart_base'], function(Base) {
 
     Bar.prototype.TYPE = 'bar';
 
+    Bar.prototype._setDefaults = function() {
+        Base.prototype._setDefaults.apply(this, arguments);
+        var axis = this.getYAxis(0, true);
+        axis.setMin(0);
+    };
+
     return Bar;
 
 });

lib/classes/chart_bar.php

@@ -33,4 +33,11 @@ defined('MOODLE_INTERNAL') || die();
  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 class chart_bar extends chart_base {
+
+    protected function set_defaults() {
+        parent::set_defaults();
+        $yaxis = $this->get_yaxis(0, true);
+        $yaxis->set_min(0);
+    }
+
 }