MDL-33728 Ensure that chooser dialogues are centred vertically

lib/yui/chooserdialogue/chooserdialogue.js

@@ -152,6 +152,7 @@ YUI.add('moodle-core-chooserdialogue', function(Y) {
             var bb = this.overlay.get('boundingBox');
 
             var winheight = bb.get('winHeight');
+            var winwidth = bb.get('winWidth');
             var offsettop = 0;
 
             // Try and set a sensible max-height -- this must be done before setting the top
@@ -187,6 +188,13 @@ YUI.add('moodle-core-chooserdialogue', function(Y) {
             // We need to set the height for the yui3-widget - can't work
             // out what we're setting at present -- shoud be the boudingBox
             bb.setStyle('top', dialoguetop + 'px');
+
+            // Calculate the left location of the chooser
+            // We don't set a minimum width in the same way as we do height as the width would be far lower than the
+            // optimal width for moodle anyway.
+            var dialoguewidth = bb.get('offsetWidth');
+            var dialogueleft = (winwidth - dialoguewidth) / 2;
+            bb.setStyle('left', dialogueleft + 'px');
         },
 
         handle_key_press : function(e) {