Inhibit suspend while a activity is shared

In some network environments, suspend/reume can make loose
messages and break collaboration. This patch inhibit suspend
when collaboration start. The implementation can be used by activities
or Sugar to inhibit suspend/resume when needed.

More information in http://dev.laptop.org/ticket/10363

Signed-off-by: Gonzalo Odiard <gonzalo@laptop.org>

src/sugar3/Makefile.am

@@ -14,6 +14,7 @@ sugar_PYTHON =		\
 	logger.py	\
 	mime.py		\
         network.py	\
+	power.py \
 	profile.py	\
 	util.py
 

src/sugar3/activity/activity.py

@@ -74,6 +74,7 @@ from telepathy.constants import CONNECTION_HANDLE_TYPE_CONTACT
 from telepathy.constants import CONNECTION_HANDLE_TYPE_ROOM
 
 from sugar3 import util
+from sugar3 import power
 from sugar3.presence import presenceservice
 from sugar3.activity.activityservice import ActivityService
 from sugar3.graphics import style
@@ -809,6 +810,10 @@ class Activity(Window, Gtk.Container):
             logging.debug('Failed to join activity: %s' % err)
             return
 
+        power_manager = power.get_power_manager()
+        if power_manager.suspend_breaks_collaboration():
+            power_manager.inhibit_suspend()
+
         self.reveal()
         self.emit('joined')
         self.__privacy_changed_cb(self.shared_activity, None)
@@ -837,6 +842,10 @@ class Activity(Window, Gtk.Container):
 
         activity.props.name = self._jobject.metadata['title']
 
+        power_manager = power.get_power_manager()
+        if power_manager.suspend_breaks_collaboration():
+            power_manager.inhibit_suspend()
+
         self.shared_activity = activity
         self.shared_activity.connect('notify::private',
                                      self.__privacy_changed_cb)
@@ -953,6 +962,7 @@ class Activity(Window, Gtk.Container):
         dbus.service.Object.remove_from_connection(self._bus)
 
         self._session.unregister(self)
+        power.get_power_manager().shutdown()
 
     def close(self, skip_save=False):
         """Request that the activity be stopped and saved to the Journal

src/sugar3/power.py

@@ -0,0 +1,85 @@
+# Copyright (C) 2014, Sugarlabs
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2 of the License, or (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library; if not, write to the
+# Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+# Boston, MA 02111-1307, USA.
+
+import os
+import logging
+
+_POWERD_INHIBIT_DIR = '/var/run/powerd-inhibit-suspend'
+
+_power_manager = None
+
+
+def get_power_manager():
+    global _power_manager
+    if _power_manager is None:
+        _power_manager = PowerManager()
+    return _power_manager
+
+
+class PowerManager():
+    """ control of powerd idle suspend,
+        reference counted,
+        does nothing if powerd is not present
+    """
+
+    def __init__(self):
+        self._suspend_inhibit_counter = 0
+
+    def __del__(self):
+        self._remove_flag_file()
+
+    def suspend_breaks_collaboration(self):
+        return True
+
+    def inhibit_suspend(self):
+        if not os.path.exists(_POWERD_INHIBIT_DIR):
+            return
+
+        if self._suspend_inhibit_counter == 0:
+            path = os.path.join(_POWERD_INHIBIT_DIR, str(os.getpid()))
+            try:
+                with open(path, 'w') as flag_file:
+                    flag_file.write('')
+            except IOError:
+                logging.error("Inhibit Suspend: Could not create file %s",
+                              path)
+
+        self._suspend_inhibit_counter += 1
+
+    def restore_suspend(self):
+        self._suspend_inhibit_counter -= 1
+        if self._suspend_inhibit_counter > 0:
+            return
+        self._remove_flag_file()
+
+    def is_suspend_inhibited(self):
+        return self._suspend_inhibit_counter > 0
+
+    def shutdown(self):
+        """
+        This method clean the flag file if exists,
+        is already called when the activity is closed.
+        """
+        self._remove_flag_file()
+
+    def _remove_flag_file(self):
+        path = os.path.join(_POWERD_INHIBIT_DIR, str(os.getpid()))
+        try:
+            os.unlink(path)
+        except IOError:
+            logging.error("Inhibit Suspend: Could not delete file %s", path)
+        self._suspend_inhibit_counter = 0