Notify plugins on program closing

EDMarketConnector.py

@@ -819,6 +819,7 @@ class AppWindow:
         hotkeymgr.unregister()
         interactions.close()
         monitor.close()
+        plug.notify_stop()
         self.eddn.close()
         self.updater.close()
         self.session.close()

PLUGINS.md

@@ -32,6 +32,18 @@ def plugin_start():
 
 Any errors or print statements from your plugin will appear in `%TMP%\EDMarketConnector.log` on Windows or `$TMPDIR/EDMarketConnector.log` on Mac.
 
+This gets called when the user closes the program:
+
+```python
+def plugin_stop():
+    """
+    EDMC is closing
+    """
+    print "Farewell cruel world!"
+```
+
+If your plugin uses one or more threads to handle Events then stop and join() the threads before returning from this function.
+
 # Plugin Hooks
 ## Configuration 
 
@@ -94,7 +106,7 @@ this.status["text"] = "Happy!"
 
 ## Events
 
-Once you have created your plugin and EDMC has loaded it there are four other functions you can define to be notified by EDMC when something happens: `journal_entry()`, `interaction()`, `cmdr_data()` and `prefs_changed()`.
+Once you have created your plugin and EDMC has loaded it there are three other functions you can define to be notified by EDMC when something happens: `journal_entry()`, `interaction()` and `cmdr_data()`.
 
 Your events all get called on the main tkinter loop so be sure not to block for very long or the EDMC will appear to freeze. If you have a long running operation then you should take a look at how to do background updates in tkinter - http://effbot.org/zone/tkinter-threads.htm
 

plug.py

@@ -132,6 +132,24 @@ def load_plugins():
     imp.release_lock()
 
 
+def notify_stop():
+    """
+    Notify each plugin that the program is closing.
+    If your plugin uses threads then stop and join() them before returning.
+    versionadded:: 2.3.7
+    """
+    error = None
+    for plugin in PLUGINS:
+        plugin_stop = plugin._get_func('plugin_stop')
+        if plugin_stop:
+            try:
+                newerror = plugin_stop()
+                error = error or newerror
+            except:
+                print_exc()
+    return error
+
+
 def notify_prefs_cmdr_changed(cmdr, is_beta):
     """
     Notify each plugin that the Cmdr has been changed while the settings dialog is open.