cmds: Avoid PyQt4 threading issues

Keep a reference to the QRunnable so that we do not segfault PyQt4 when
the task goes out of scope.  This problem occurs with older versions of
PyQt4 (e.g. 4.6.2).  Newer versions of PyQt4 do not have this problem.

Signed-off-by: David Aguilar <davvid@gmail.com>

Author: davvid

cola/cmds.py

@@ -1048,16 +1048,23 @@ def runner(*local_args, **local_opts):
     return runner
 
 
+# Holds a reference to background tasks to avoid PyQt4 segfaults
+ALL_TASKS = set()
+
+
 def background(parent, cls, *args, **opts):
     cmd = cls(*args, **opts)
     task = AsyncCommand(parent, cmd)
+    ALL_TASKS.add(task)
     QtCore.QThreadPool.globalInstance().start(task)
 
 
+
 class RunCommand(QtCore.QObject):
-    def __init__(self, cmd, parent):
+    def __init__(self, cmd, task, parent):
         QtCore.QObject.__init__(self, parent)
         self.cmd = cmd
+        self.task = task
         self.connect(self, SIGNAL('command_ready'), self.do)
 
     def run(self):
@@ -1066,12 +1073,16 @@ def run(self):
 
     def do(self):
         do_cmd(self.cmd)
+        try:
+            ALL_TASKS.remove(self.task)
+        except:
+            pass
 
 
 class AsyncCommand(QtCore.QRunnable):
     def __init__(self, parent, cmd):
         QtCore.QRunnable.__init__(self)
-        self.runner = RunCommand(cmd, parent)
+        self.runner = RunCommand(cmd, self, parent)
 
     def run(self):
         self.runner.run()