Add machine-readable pagination using HTML4.01 `<link rel="next">`, etc.

These extra `<link>` elements only appear on pages where pagination
makes sense. They trigger functionality in some user agents, such as
Opera's Navigation Bar for more easily navigating forward and backwards
across a paged set of notices, messages, or group lists, etc.

13 files changed, 273 insertions, 1 deletions

diff --git a/actions/all.php b/actions/all.php
index d75d1b946..76b1bbcdf 100644
--- a/actions/all.php
+++ b/actions/all.php
@@ -78,6 +78,28 @@ class AllAction extends Action
                                      'title' => sprintf(_('Feed for friends of %s'), $this->user->nickname)));
     }
 
+    /**
+     * Output document relationship links
+     *
+     * @return void
+     */
+    function showRelationshipLinks()
+    {
+        // Machine-readable pagination
+        if ($this->page > 1) {
+            $this->element('link', array('rel' => 'next',
+                                         'href' => common_local_url('all',
+                                                                    array('nickname' => $this->user->nickname,
+                                                                          'page' => $this->page - 1)),
+                                         'title' => _('Next Notices')));
+        }
+        $this->element('link', array('rel' => 'prev',
+                                     'href' => common_local_url('all',
+                                                                array('nickname' => $this->user->nickname,
+                                                                      'page' => $this->page + 1)),
+                                     'title' => _('Previous Notices')));
+    }
+
     function showLocalNav()
     {
         $nav = new PersonalGroupNav($this);
diff --git a/actions/favorited.php b/actions/favorited.php
index fd5ff413c..367fb6dd6 100644
--- a/actions/favorited.php
+++ b/actions/favorited.php
@@ -195,4 +195,24 @@ class FavoritedAction extends Action
         $this->pagination($this->page > 1, $cnt > NOTICES_PER_PAGE,
                           $this->page, 'favorited');
     }
+
+    /**
+     * Output document relationship links
+     *
+     * @return void
+     */
+    function showRelationshipLinks()
+    {
+        // Machine-readable pagination
+        if ($this->page > 1) {
+            $this->element('link', array('rel' => 'next',
+                                         'href' => common_local_url('favorited',
+                                                                    array('page' => $this->page - 1)),
+                                         'title' => _('Next Notices')));
+        }
+        $this->element('link', array('rel' => 'prev',
+                                     'href' => common_local_url('favorited',
+                                                                array('page' => $this->page + 1)),
+                                     'title' => _('Previous Notices')));
+    }
 }
diff --git a/actions/groupmembers.php b/actions/groupmembers.php
index 00f43a9f5..2b2bdba93 100644
--- a/actions/groupmembers.php
+++ b/actions/groupmembers.php
@@ -137,4 +137,26 @@ class GroupmembersAction extends Action
                           $this->page, 'groupmembers',
                           array('nickname' => $this->group->nickname));
     }
-}
\ No newline at end of file
+
+    /**
+     * Output document relationship links
+     *
+     * @return void
+     */
+    function showRelationshipLinks()
+    {
+        // Machine-readable pagination
+        if ($this->page > 1) {
+            $this->element('link', array('rel' => 'next',
+                                         'href' => common_local_url('groupmembers',
+                                                                    array('nickname' => $this->group->nickname,
+                                                                          'page' => $this->page - 1)),
+                                         'title' => _('Next Group Members')));
+        }
+        $this->element('link', array('rel' => 'prev',
+                                     'href' => common_local_url('groupmembers',
+                                                                array('nickname' => $this->group->nickname,
+                                                                      'page' => $this->page + 1)),
+                                     'title' => _('Previous Group Members')));
+    }
+}
diff --git a/actions/groups.php b/actions/groups.php
index 39dc2232b..b0bf7cfc2 100644
--- a/actions/groups.php
+++ b/actions/groups.php
@@ -129,4 +129,24 @@ class GroupsAction extends Action
         $gbm = new GroupsByMembersSection($this);
         $gbm->show();
     }
+
+    /**
+     * Output document relationship links
+     *
+     * @return void
+     */
+    function showRelationshipLinks()
+    {
+        // Machine-readable pagination
+        if ($this->page > 1) {
+            $this->element('link', array('rel' => 'next',
+                                         'href' => common_local_url('groups',
+                                                                    array('page' => $this->page - 1)),
+                                         'title' => _('Next Groups')));
+        }
+        $this->element('link', array('rel' => 'prev',
+                                     'href' => common_local_url('groups',
+                                                                array('page' => $this->page + 1)),
+                                     'title' => _('Previous Groups')));
+    }
 }
diff --git a/actions/inbox.php b/actions/inbox.php
index b553ab26c..d12f3f20a 100644
--- a/actions/inbox.php
+++ b/actions/inbox.php
@@ -64,6 +64,28 @@ class InboxAction extends MailboxAction
     }
 
     /**
+     * Output document relationship links
+     *
+     * @return void
+     */
+    function showRelationshipLinks()
+    {
+        // Machine-readable pagination
+        if ($this->page > 1) {
+            $this->element('link', array('rel' => 'next',
+                                         'href' => common_local_url('inbox',
+                                                                    array('nickname' => $this->user->nickname,
+                                                                          'page' => $this->page - 1)),
+                                         'title' => _('Next Messages')));
+        }
+        $this->element('link', array('rel' => 'prev',
+                                     'href' => common_local_url('inbox',
+                                                                array('nickname' => $this->user->nickname,
+                                                                      'page' => $this->page + 1)),
+                                     'title' => _('Previous Messages')));
+    }
+
+    /**
      * Retrieve the messages for this user and this page
      *
      * Does a query for the right messages
diff --git a/actions/outbox.php b/actions/outbox.php
index c8d7f2812..043b74edc 100644
--- a/actions/outbox.php
+++ b/actions/outbox.php
@@ -63,6 +63,28 @@ class OutboxAction extends MailboxAction
     }
 
     /**
+     * Output document relationship links
+     *
+     * @return void
+     */
+    function showRelationshipLinks()
+    {
+        // Machine-readable pagination
+        if ($this->page > 1) {
+            $this->element('link', array('rel' => 'next',
+                                         'href' => common_local_url('outbox',
+                                                                    array('nickname' => $this->user->nickname,
+                                                                          'page' => $this->page - 1)),
+                                         'title' => _('Next Messages')));
+        }
+        $this->element('link', array('rel' => 'prev',
+                                     'href' => common_local_url('outbox',
+                                                                array('nickname' => $this->user->nickname,
+                                                                      'page' => $this->page + 1)),
+                                     'title' => _('Previous Messages')));
+    }
+
+    /**
      * retrieve the messages for this user and this page
      *
      * Does a query for the right messages
diff --git a/actions/public.php b/actions/public.php
index cc6537f74..25889eee5 100644
--- a/actions/public.php
+++ b/actions/public.php
@@ -128,6 +128,26 @@ class PublicAction extends Action
     }
 
     /**
+     * Output document relationship links
+     *
+     * @return void
+     */
+    function showRelationshipLinks()
+    {
+        // Machine-readable pagination
+        if ($this->page > 1) {
+            $this->element('link', array('rel' => 'next',
+                                         'href' => common_local_url('public',
+                                                                    array('page' => $this->page - 1)),
+                                         'title' => _('Next Notices')));
+        }
+        $this->element('link', array('rel' => 'prev',
+                                     'href' => common_local_url('public',
+                                                                array('page' => $this->page + 1)),
+                                     'title' => _('Previous Notices')));
+    }
+
+    /**
      * Extra head elements
      *
      * We include a <meta> element linking to the publicxrds page, for OpenID
diff --git a/actions/replies.php b/actions/replies.php
index 7eff74a66..5ae99e165 100644
--- a/actions/replies.php
+++ b/actions/replies.php
@@ -142,6 +142,28 @@ class RepliesAction extends Action
     }
 
     /**
+     * Output document relationship links
+     *
+     * @return void
+     */
+    function showRelationshipLinks()
+    {
+        // Machine-readable pagination
+        if ($this->page > 1) {
+            $this->element('link', array('rel' => 'next',
+                                         'href' => common_local_url('replies',
+                                                                    array('nickname' => $this->user->nickname,
+                                                                          'page' => $this->page - 1)),
+                                         'title' => _('Next Notices')));
+        }
+        $this->element('link', array('rel' => 'prev',
+                                     'href' => common_local_url('replies',
+                                                                array('nickname' => $this->user->nickname,
+                                                                      'page' => $this->page + 1)),
+                                     'title' => _('Previous Notices')));
+    }
+
+    /**
      * show the personal group nav
      *
      * @return void
diff --git a/actions/showfavorites.php b/actions/showfavorites.php
index 31479e1a7..f0297172a 100644
--- a/actions/showfavorites.php
+++ b/actions/showfavorites.php
@@ -154,6 +154,28 @@ class ShowfavoritesAction extends Action
     }
 
     /**
+     * Output document relationship links
+     *
+     * @return void
+     */
+    function showRelationshipLinks()
+    {
+        // Machine-readable pagination
+        if ($this->page > 1) {
+            $this->element('link', array('rel' => 'next',
+                                         'href' => common_local_url('showfavorites',
+                                                                    array('nickname' => $this->user->nickname,
+                                                                          'page' => $this->page - 1)),
+                                         'title' => _('Next Favorite Notices')));
+        }
+        $this->element('link', array('rel' => 'prev',
+                                     'href' => common_local_url('showfavorites',
+                                                                array('nickname' => $this->user->nickname,
+                                                                      'page' => $this->page + 1)),
+                                     'title' => _('Previous Favorite Notices')));
+    }
+
+    /**
      * show the personal group nav
      *
      * @return void
diff --git a/actions/showgroup.php b/actions/showgroup.php
index 7bc68fbc6..7599a8de6 100644
--- a/actions/showgroup.php
+++ b/actions/showgroup.php
@@ -327,6 +327,28 @@ class ShowgroupAction extends Action
     }
 
     /**
+     * Output document relationship links
+     *
+     * @return void
+     */
+    function showRelationshipLinks()
+    {
+        // Machine-readable pagination
+        if ($this->page > 1) {
+            $this->element('link', array('rel' => 'next',
+                                         'href' => common_local_url('showgroup',
+                                                                    array('nickname' => $this->group->nickname,
+                                                                          'page' => $this->page - 1)),
+                                         'title' => _('Next Notices')));
+        }
+        $this->element('link', array('rel' => 'prev',
+                                     'href' => common_local_url('showgroup',
+                                                                array('nickname' => $this->group->nickname,
+                                                                      'page' => $this->page + 1)),
+                                     'title' => _('Previous Notices')));
+    }
+
+    /**
      * Fill in the sidebar.
      *
      * @return void
diff --git a/actions/showstream.php b/actions/showstream.php
index 28bb8453f..11615ebb0 100644
--- a/actions/showstream.php
+++ b/actions/showstream.php
@@ -195,6 +195,28 @@ class ShowstreamAction extends Action
                              $this->user->nickname)));
     }
 
+    /**
+     * Output document relationship links
+     *
+     * @return void
+     */
+    function showRelationshipLinks()
+    {
+        // Machine-readable pagination
+        if ($this->page > 1) {
+            $this->element('link', array('rel' => 'next',
+                                         'href' => common_local_url('showstream',
+                                                                    array('nickname' => $this->user->nickname,
+                                                                          'page' => $this->page - 1)),
+                                         'title' => _('Next Notices')));
+        }
+        $this->element('link', array('rel' => 'prev',
+                                     'href' => common_local_url('showstream',
+                                                                array('nickname' => $this->user->nickname,
+                                                                      'page' => $this->page + 1)),
+                                     'title' => _('Previous Notices')));
+    }
+
     function extraHead()
     {
         // FOAF
diff --git a/actions/tag.php b/actions/tag.php
index 4401f892a..f71f6d342 100644
--- a/actions/tag.php
+++ b/actions/tag.php
@@ -69,6 +69,28 @@ class TagAction extends Action
                                      'title' => sprintf(_('Feed for tag %s'), $this->tag)));
     }
 
+    /**
+     * Output document relationship links
+     *
+     * @return void
+     */
+    function showRelationshipLinks()
+    {
+        // Machine-readable pagination
+        if ($this->page > 1) {
+            $this->element('link', array('rel' => 'next',
+                                         'href' => common_local_url('tag',
+                                                                    array('tag' => $this->tag,
+                                                                          'page' => $this->page - 1)),
+                                         'title' => _('Next Notices')));
+        }
+        $this->element('link', array('rel' => 'prev',
+                                     'href' => common_local_url('tag',
+                                                                array('tag' => $this->tag,
+                                                                      'page' => $this->page + 1)),
+                                     'title' => _('Previous Notices')));
+    }
+
     function showPageNotice()
     {
         return sprintf(_('Messages tagged "%s", most recent first'), $this->tag);
diff --git a/lib/action.php b/lib/action.php
index c4172ada1..ab51d0252 100644
--- a/lib/action.php
+++ b/lib/action.php
@@ -111,6 +111,7 @@ class Action extends HTMLOutputter // lawsuit
         $this->showTitle();
         $this->showStylesheets();
         $this->showScripts();
+        $this->showRelationshipLinks();
         $this->showOpenSearch();
         $this->showFeeds();
         $this->showDescription();
@@ -194,6 +195,19 @@ class Action extends HTMLOutputter // lawsuit
     }
 
     /**
+     * Show document relationship links
+     *
+     * SHOULD overload
+     *
+     * @return nothing
+     */
+    function showRelationshipLinks()
+    {
+        // output <link> elements with appropriate HTML4.01 link types:
+        // http://www.w3.org/TR/html401/types.html#type-links
+    }
+
+    /**
      * Show OpenSearch headers
      *
      * @return nothing