Extensions: Add on_load() / on_unload() support

This allows extensions to hook into stuff and remove
the hooks when the extension is unloaded.

examples/hello_world.py

@@ -0,0 +1,39 @@
+
+# Use a logger for debug output - this will be managed by gPodder
+import logging
+logger = logging.getLogger(__name__)
+
+# Provide some metadata that will be displayed in the gPodder GUI
+__title__ = 'Hello World Extension'
+__description__ = 'Explain in one sentence what this extension does.'
+__only_for__ = 'gtk, cli, qml'
+__author__ = 'Thomas Perl <m@thp.io>'
+
+class gPodderExtension:
+    # The extension will be instantiated the first time it's used
+    # You can do some sanity checks here and raise an Exception if
+    # you want to prevent the extension from being loaded..
+    def __init__(self, container):
+        self.container = container
+
+    # This function will be called when the extension is enabled or
+    # loaded. This is when you want to create helper objects or hook
+    # into various parts of gPodder.
+    def on_load(self):
+        logger.info('Extension is being loaded.')
+        print '='*40
+        print 'container:', self.container
+        print 'container.manager:', self.container.manager
+        print 'container.config:', self.container.config
+        print 'container.manager.core:', self.container.manager.core
+        print 'container.manager.core.db:', self.container.manager.core.db
+        print 'container.manager.core.config:', self.container.manager.core.config
+        print 'container.manager.core.model:', self.container.manager.core.model
+        print '='*40
+
+    # This function will be called when the extension is disabled or
+    # when gPodder shuts down. You can use this to destroy/delete any
+    # objects that you created in on_load().
+    def on_unload(self):
+        logger.info('Extension is being unloaded.')
+

src/gpodder/builtins/notification.py

@@ -41,8 +41,15 @@ if pynotify is None:
 else:
     class gPodderExtension(object):
         def __init__(self, container):
+            self.container = container
+
+        def on_load(self):
             pynotify.init('gPodder')
-            logger.info('Notification plug-in loaded successfully.')
+            logger.info('PyNotify initialized.')
+
+        def on_unload(self):
+            logger.info('Uninitializing PyNotify.')
+            pynotify.uninit()
 
         def on_notification_show(self, title, message):
             notify = pynotify.Notification(title, message, gpodder.icon_file)

src/gpodder/core.py

@@ -53,6 +53,9 @@ class Core(object):
         self.config.mygpo.device.type = util.detect_device_type()
 
     def shutdown(self):
+        # Notify all extensions that we are being shut down
+        gpodder.user_extensions.shutdown()
+
         # Close the database and store outstanding changes
         self.db.close()
 

src/gpodder/extensions.py

@@ -152,28 +152,24 @@ class ExtensionContainer(object):
         extension_py = open(filename).read()
         return dict(re.findall("__([a-z_]+)__ = '([^']+)'", extension_py))
 
-    def _load_module(self):
-        basename, extension = os.path.splitext(os.path.basename(self.filename))
-        fp = open(self.filename, 'r')
-        module = imp.load_module(basename, fp, self.filename,
-                (extension, 'r', imp.PY_SOURCE))
-        fp.close()
-
-        # Remove the .pyc file if it was created during import
-        util.delete_file(self.filename + 'c')
-
-        return module
-
     def set_enabled(self, enabled):
-        if enabled:
+        if enabled and not self.enabled:
             try:
                 self.load_extension()
                 self.enabled = True
+                if hasattr(self.module, 'on_load'):
+                    self.module.on_load()
             except Exception, exception:
                 logger.error('Cannot load %s from %s: %s', self.name,
                         self.filename, exception, exc_info=True)
                 self.enabled = False
-        else:
+        elif not enabled and self.enabled:
+            try:
+                if hasattr(self.module, 'on_unload'):
+                    self.module.on_unload()
+            except Exception, exception:
+                logger.error('Failed to on_unload %s: %s', self.name,
+                        exception, exc_info=True)
             self.enabled = False
 
     def load_extension(self):
@@ -187,7 +183,15 @@ class ExtensionContainer(object):
                     self.name, self.metadata.only_for)
             return
 
-        module_file = self._load_module()
+        basename, extension = os.path.splitext(os.path.basename(self.filename))
+        fp = open(self.filename, 'r')
+        module_file = imp.load_module(basename, fp, self.filename,
+                (extension, 'r', imp.PY_SOURCE))
+        fp.close()
+
+        # Remove the .pyc file if it was created during import
+        util.delete_file(self.filename + 'c')
+
         self.default_config = getattr(module_file, 'DefaultConfig', {})
         self.parameters = getattr(module_file, 'Parameters', {})
 
@@ -214,6 +218,10 @@ class ExtensionManager(object):
                 container.set_enabled(True)
             self.containers.append(container)
 
+    def shutdown(self):
+        for container in self.containers:
+            container.set_enabled(False)
+
     def _config_value_changed(self, name, old_value, new_value):
         if name == 'extensions.enabled':
             for container in self.containers: