Add preferences link to /lists homepage (#310)

* Added clarifying inline comments

* Added link to preferences page

* Added default value for constant SHOW_PREFERENCESLINK

* Documented constants relating to public subscribe page links

Author: Sam Tuke

public_html/lists/admin/init.php

@@ -257,6 +257,9 @@
 if (!defined('UNSUBSCRIBE_JUMPOFF')) {
     define('UNSUBSCRIBE_JUMPOFF', 1);
 }
+if (!defined('SHOW_PREFERENCESLINK')) {
+    define('SHOW_PREFERENCESLINK', true);
+}
 if (!defined('SHOW_UNSUBSCRIBELINK')) {
     define('SHOW_UNSUBSCRIBELINK', true);
 }

public_html/lists/config/config_extended.php

@@ -440,6 +440,15 @@
 // see also https://mantis.phplist.com/view.php?id=15274
 define('PREFERENCEPAGE_SHOW_PRIVATE_LISTS', 0);
 
+// Show the link(s) to subscribe page(s) on the phpList public homepage (lists/)
+define('SHOW_SUBSCRIBELINK', true);
+
+// Show link to the preferences page on the phpList public homepage (lists/)
+define('SHOW_PREFERENCESLINK', true);
+
+// Show link to the unsubscribe page on the phpList public homepage (lists/)
+define('SHOW_UNSUBSCRIBELINK', true);
+
 // Show 'All Subscribers' section on Subscriber Lists page
 // This flag enabled will show a list called “All subscribers” on the 
 // Subscriber Lists page that has all subscribers in the system as members. 

public_html/lists/index.php

@@ -333,9 +333,12 @@
         FileNotFound();
     }
 } else {
+    // If no particular page was requested then show the default
     echo '<title>'.$GLOBALS['strSubscribeTitle'].'</title>';
     echo $pagedata['header'];
     $req = Sql_Query(sprintf('select * from %s where active', $tables['subscribepage']));
+        
+    // If active subscribe pages exist then list them
     if (Sql_Affected_Rows()) {
         while ($row = Sql_Fetch_Array($req)) {
             $intro = Sql_Fetch_Row_Query(sprintf('select data from %s where id = %d and name = "intro"',
@@ -346,12 +349,19 @@
                     strip_tags(stripslashes($row['title'])));
             }
         }
+    // If no active subscribe page exist then print link to default
     } else {
         if (SHOW_SUBSCRIBELINK) {
             printf('<p><a href="'.getConfig('subscribeurl').'">%s</a></p>', $strSubscribeTitle);
         }
     }
 
+    // Print preferences page link
+    if (SHOW_PREFERENCESLINK) {
+        printf('<p><a href="'.getConfig('preferencesurl').'">%s</a></p>', $strPreferencesTitle);
+    }
+
+    // Print unsubscribe page link
     if (SHOW_UNSUBSCRIBELINK) {
         printf('<p><a href="'.getConfig('unsubscribeurl').'">%s</a></p>', $strUnsubscribeTitle);
     }