add kernel_started signal to QtKernelManager

for use notifying of kernel start (principally kernel restart)

IPython/frontend/qt/base_frontend_mixin.py

@@ -25,6 +25,7 b' class BaseFrontendMixin(object):'
         # Disconnect the old kernel manager, if necessary.
         old_manager = self._kernel_manager
         if old_manager is not None:
+            old_manager.started_kernel.disconnect(self._started_kernel)
             old_manager.started_channels.disconnect(self._started_channels)
             old_manager.stopped_channels.disconnect(self._stopped_channels)
 
@@ -45,6 +46,7 b' class BaseFrontendMixin(object):'
             return
 
         # Connect the new kernel manager.
+        kernel_manager.started_kernel.connect(self._started_kernel)
         kernel_manager.started_channels.connect(self._started_channels)
         kernel_manager.stopped_channels.connect(self._stopped_channels)
 
@@ -78,6 +80,11 b' class BaseFrontendMixin(object):'
             The time since the heartbeat was last received.
         """
 
+    def _started_kernel(self):
+        """Called when the KernelManager starts (or restarts) the kernel subprocess.
+        Channels may or may not be running at this point.
+        """
+
     def _started_channels(self):
         """ Called when the KernelManager channels have started listening or
             when the frontend is assigned an already listening KernelManager.

IPython/frontend/qt/kernelmanager.py

@@ -183,6 +183,9 b' class QtKernelManager(KernelManager, SuperQObject):'
     __metaclass__ = MetaQObjectHasTraits
 
     # Emitted when the kernel manager has started listening.
+    started_kernel = QtCore.Signal()
+
+    # Emitted when the kernel manager has started listening.
     started_channels = QtCore.Signal()
 
     # Emitted when the kernel manager has stopped listening.
@@ -206,6 +209,7 b' class QtKernelManager(KernelManager, SuperQObject):'
         if self._shell_channel is not None:
             self._shell_channel.reset_first_reply()
         super(QtKernelManager, self).start_kernel(*args, **kw)
+        self.started_kernel.emit()
 
     #------ Channel management -------------------------------------------------