Basic Offline mode support (bug 107)

Detect network connections on Linux (still need to find a way to
implement it for Windows and OS X - on these platforms, this
implementation acts as if the connection is always available).

We might need to use this in more places in the code, but for starters
this should work nicely.

The Linux implementation assumes the "ip" command is available.

share/gpodder/ui/qml/Main.qml

@@ -425,10 +425,19 @@ Image {
 
         Label {
             id: messageDialogText
-            anchors.centerIn: parent
+            anchors {
+                left: parent.left
+                right: parent.right
+                verticalCenter: parent.verticalCenter
+                leftMargin: Config.largeSpacing
+                rightMargin: Config.largeSpacing
+            }
             color: 'white'
             font.pixelSize: 20
             font.bold: true
+            width: parent.width
+            horizontalAlignment: Text.AlignHCenter
+            wrapMode: Text.WordWrap
         }
     }
 

src/gpodder/gtkui/main.py

@@ -2339,6 +2339,11 @@ def on_btnCancelFeedUpdate_clicked(self, widget):
 
     def update_feed_cache(self, channels=None,
                           show_new_episodes_dialog=True):
+        if not util.connection_available():
+            self.show_message(_('Please connect to a network, then try again.'),
+                    _('No network connection'), important=True)
+            return
+
         # Fix URLs if mygpo has rewritten them
         self.rewrite_urls_mygpo()
 
@@ -3319,6 +3324,9 @@ def restart_auto_update_timer(self):
                     interval, self._on_auto_update_timer)
 
     def _on_auto_update_timer(self):
+        if not util.connection_available():
+            logger.debug('Skipping auto update (no connection available)')
+
         logger.debug('Auto update timer fired.')
         self.update_feed_cache()
 

src/gpodder/qmlui/__init__.py

@@ -474,6 +474,9 @@ def find_episode(self, podcast_url, episode_url):
 
     @Slot()
     def updateAllPodcasts(self):
+        if not self.request_connection():
+            return
+
         # Process episode actions received from gpodder.net
         def merge_proc(self):
             self.root.start_progress(_('Merging episode actions...'))
@@ -497,11 +500,28 @@ def find_episode(podcast_url, episode_url, counter):
             if not podcast.pause_subscription:
                 podcast.qupdate(finished_callback=self.update_subset_stats)
 
+    def request_connection(self):
+        """Request an internet connection
+
+        Returns True if a connection is available, False otherwise
+        """
+        if not util.connection_available():
+            # TODO: Try to request the network connection dialog, and wait
+            # for a connection - if a connection is available, return True
+
+            self.root.show_message('\n\n'.join((_('No network connection'),
+                _('Please connect to a network, then try again.'))))
+            return False
+
+        return True
+
     @Slot(int)
     def contextMenuResponse(self, index):
         assert index < len(self.context_menu_actions)
         action = self.context_menu_actions[index]
         if action.action == 'update':
+            if not self.request_connection():
+                return
             podcast = action.target
             if not podcast.pause_subscription:
                 podcast.qupdate(finished_callback=self.update_subset_stats)

src/gpodder/util.py

@@ -1628,15 +1628,51 @@ def run_in_background(function, daemon=False):
     return thread
 
 
-def website_reachable(url='http://www.google.com'):
+def linux_get_active_interfaces():
+    """Get active network interfaces using 'ip link'
+
+    Returns a list of active network interfaces or an
+    empty list if the device is offline. The loopback
+    interface is not included.
+    """
+    stdout = subprocess.check_output(['ip', 'link'])
+    return re.findall(r'\d+: ([^:]+):.*state UP', stdout)
+
+
+def connection_available():
+    """Check if an Internet connection is available
+
+    Returns True if a connection is available (or if there
+    is no way to determine the connection). Returns False
+    if no network interfaces are up (i.e. no connectivity).
+    """
+    try:
+        if gpodder.win32:
+            # FIXME: Implement for Windows
+            return True
+        elif gpodder.osx:
+            # FIXME: Implement for Mac OS X
+            return True
+        else:
+            return len(linux_get_active_interfaces()) > 0
+    except Exception, e:
+        logger.warn('Cannot get connection status: %s', e, exc_info=True)
+        return False
+
+
+def website_reachable(url):
     """
     Check if a specific website is available.
-    """  
+    """
+    if not connection_available():
+        # No network interfaces up - assume website not reachable
+        return (False, None)
+
     try:
         response = urllib2.urlopen(url, timeout=1)
         return (True, response)
     except urllib2.URLError as err:
         pass
-        
+
     return (False, None)