From 51c56af0797a967b8b426b0e4f1135cb3e19bbff Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Sun, 15 Aug 2010 11:25:19 -0600
Subject: [PATCH] Add hooks to GUI plugins for the shutdown process

---
 src/calibre/gui2/actions/__init__.py | 14 +++++++++++++-
 src/calibre/gui2/ui.py               |  6 +++---
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/src/calibre/gui2/actions/__init__.py b/src/calibre/gui2/actions/__init__.py
index bce1f283aa..9c20f2adef 100644
--- a/src/calibre/gui2/actions/__init__.py
+++ b/src/calibre/gui2/actions/__init__.py
@@ -27,7 +27,8 @@ class InterfaceAction(QObject):
     priority takes precedence.
 
     Sub-classes should implement the :meth:`genesis`, :meth:`library_moved`,
-    :meth:`location_selected` and :meth:`initialization_complete` methods.
+    :meth:`location_selected` :meth:`shutting_down`
+    and :meth:`initialization_complete` methods.
 
     Once initialized, this plugin has access to the main calibre GUI via the
     :attr:`gui` member. You can access other plugins by name, for example::
@@ -122,3 +123,14 @@ class InterfaceAction(QObject):
         completed.
         '''
         pass
+
+    def shutting_down(self):
+        '''
+        Called once per plugin when the main GUI is in the process of shutting
+        down. Release any used resources, but try not to block the shutdown for
+        long periods of time.
+
+        :return: False to halt the shutdown. You are responsible for telling
+        the user why the shutdown was halted.
+        '''
+        return True
diff --git a/src/calibre/gui2/ui.py b/src/calibre/gui2/ui.py
index 01e9d959f9..1b918e679e 100644
--- a/src/calibre/gui2/ui.py
+++ b/src/calibre/gui2/ui.py
@@ -352,8 +352,6 @@ class Main(MainWindow, MainWindowMixin, DeviceMixin, # {{{
     def booklists(self):
         return self.memory_view.model().db, self.card_a_view.model().db, self.card_b_view.model().db
 
-
-
     def library_moved(self, newloc):
         if newloc is None: return
         db = LibraryDatabase2(newloc)
@@ -377,7 +375,6 @@ class Main(MainWindow, MainWindowMixin, DeviceMixin, # {{{
     def set_window_title(self):
         self.setWindowTitle(__appname__ + u' - ||%s||'%self.iactions['Choose Library'].library_name())
 
-
     def location_selected(self, location):
         '''
         Called when a location icon is clicked (e.g. Library)
@@ -517,6 +514,9 @@ class Main(MainWindow, MainWindowMixin, DeviceMixin, # {{{
 
 
     def shutdown(self, write_settings=True):
+        for action in self.iactions.values():
+            if not action.shutting_down():
+                return
         if write_settings:
             self.write_settings()
         self.check_messages_timer.stop()