[4.0] com_messages blank state

See joomla#33264 for instructions but this time for user orubate messages and not content

This PR requires the code from joomla#33264 to be merged first - specifically the change in libraries/src/MVC/Model/ListModel.php

Author: brianteeman

administrator/components/com_messages/src/View/Messages/HtmlView.php

@@ -79,6 +79,11 @@ public function display($tpl = null)
 		$this->filterForm    = $this->get('FilterForm');
 		$this->activeFilters = $this->get('ActiveFilters');
 
+		if (!count($this->items) && $this->get('IsBlankSlate'))
+		{
+			$this->setLayout('blankstate');
+		}
+
 		// Check for errors.
 		if (count($errors = $this->get('Errors')))
 		{

administrator/language/en-GB/com_messages.ini

@@ -5,6 +5,10 @@
 
 COM_MESSAGES="Messaging"
 COM_MESSAGES_ADD="New Private Message"
+COM_MESSAGES_BLANKSTATE_TITLE="There are no messages for you in your inbox."
+COM_MESSAGES_BLANKSTATE_REQUESTS="Send messages to other administrators on your site and read their replies."
+COM_MESSAGES_BLANKSTATE_BUTTON_ADD="Send a message"
+COM_MESSAGES_BLANKSTATE_BUTTON_LEARNMORE="Learn more"
 COM_MESSAGES_CONFIG_SAVED="Configuration saved."
 COM_MESSAGES_CONFIGURATION="Messages: Options"
 COM_MESSAGES_ERR_INVALID_USER="Invalid user"

libraries/src/MVC/Model/ListModel.php

@@ -148,7 +148,28 @@ public function __construct($config = array(), MVCFactoryInterface $factory = nu
 			$this->listForbiddenList = array_merge($this->listBlacklist, $this->listForbiddenList);
 		}
 	}
-
+	/**
+	 * Is this a blank state, I.e: no items of this type regardless of the searched for states.
+	 *
+	 * @return boolean
+	 *
+	 * @since __DEPLOY_VERSION__
+	 */
+	public function getisBlankSlate()
+	{
+		$sql = $this->query
+			->clear('select')
+			->clear('values')
+			->clear('bounded')
+			->clear('limit')
+			->clear('order')
+			->clear('where')
+			->select('count(*)');
+
+		$this->_db->setQuery($sql);
+
+		return !($this->_db->loadResult() > 0);
+	}
 	/**
 	 * Method to cache the last query constructed.
 	 *