[kupfer] plugin_support: Conveniece function to check for D-Bus

[Ulrik Sverdrup <usverdrup src gnome org>]

commit 51b103649a5634de7ef9eebf76e2766537146f43
Author: Ulrik Sverdrup <ulrik sverdrup gmail com>
Date:   Fri Nov 27 14:06:39 2009 +0100

    plugin_support: Conveniece function to check for D-Bus
    
    """
    Check if a connection to the D-Bus daemon is available,
    else raise ImportError with an explanatory error message.
    
    For plugins that can not be used without contact with D-Bus;
    if this check is used, the plugin may use D-Bus and assume it
    is available in the Plugin's code.
    """

 kupfer/plugin_support.py |   26 ++++++++++++++++++++++++++
 1 files changed, 26 insertions(+), 0 deletions(-)
---
diff --git a/kupfer/plugin_support.py b/kupfer/plugin_support.py
index 5c17274..c82b098 100644
--- a/kupfer/plugin_support.py
+++ b/kupfer/plugin_support.py
@@ -79,3 +79,29 @@ class PluginSettings (pretty.OutputMixin):
 	def get_tooltip(self, key):
 		"""Return tooltip string for setting @key (if any)"""
 		return self.setting_descriptions[key].get("tooltip")
+
+# Plugin convenience functions for dependencies
+
+_has_dbus_connection = None
+
+def check_dbus_connection():
+	"""
+	Check if a connection to the D-Bus daemon is available,
+	else raise ImportError with an explanatory error message.
+
+	For plugins that can not be used without contact with D-Bus;
+	if this check is used, the plugin may use D-Bus and assume it
+	is available in the Plugin's code.
+	"""
+	global _has_dbus_connection
+	if _has_dbus_connection is None:
+		import dbus
+		try:
+			dbus.Bus()
+			_has_dbus_connection = True
+		except dbus.DBusException, err:
+			_has_dbus_connection = False
+	if not _has_dbus_connection:
+		raise ImportError(_("No D-Bus connection to desktop session"))
+
+