FIX: destroy figs in python when destroyed in js

- only actually closes the figure (in the mpl sense) if all of the managers active comms are dead - closes figure when all visible copies are removed from dom - eliminates many of the [IPKernelApp] ERROR | No such comm: XXXX errors closes #4841
matplotlib · jenshnielsen · Aug 17, 2015 · May 22, 2015 · Jul 5, 2015 · Jul 23, 2015
commit 436dfdbc4cb6b4a9cd9868b4dd36d60cdcc7da97
diff --git a/lib/matplotlib/backends/backend_nbagg.py b/lib/matplotlib/backends/backend_nbagg.py
@@ -166,16 +166,22 @@ def _create_comm(self):

    def destroy(self):
        self._send_event('close')
-        for comm in self.web_sockets.copy():
+        # need to copy comms as callbacks will modify this list
+        for comm in list(self.web_sockets):
            comm.on_close()
+        self.clearup_closed()

    def clearup_closed(self):
        """Clear up any closed Comms."""
        self.web_sockets = set([socket for socket in self.web_sockets
                                if socket.is_open()])

        if len(self.web_sockets) == 0:
-            self.manager.canvas.close_event()
+            self.canvas.close_event()
+
+    def remove_comm(self, comm_id):
+        self.web_sockets = set([socket for socket in self.web_sockets
+                                if not socket.comm.comm_id == comm_id])


 class TimerTornado(TimerBase):
@@ -278,15 +284,27 @@ def __init__(self, manager):
        self.comm.on_msg(self.on_message)

        manager = self.manager
-        self.comm.on_close(lambda close_message: manager.clearup_closed())
+        self._ext_close = False
+
+        def _on_close(close_message):
+            self._ext_close = True
+            manager.remove_comm(close_message['content']['comm_id'])
+            manager.clearup_closed()
+
+        self.comm.on_close(_on_close)

    def is_open(self):
-        return not self.comm._closed
+        return not (self._ext_close or self.comm._closed)

    def on_close(self):
        # When the socket is closed, deregister the websocket with
        # the FigureManager.
-        self.comm.close()
+        if self.is_open():
+            try:
+                self.comm.close()
+            except KeyError:
+                # apparently already cleaned it up?
+                pass

    def send_json(self, content):
        self.comm.send({'data': json.dumps(content)})
@@ -309,6 +327,7 @@ def on_message(self, message):
        message = json.loads(message['content']['data'])
        if message['type'] == 'closing':
            self.on_close()
+            self.manager.clearup_closed()
        elif message['type'] == 'supports_binary':
            self.supports_binary = message['value']
        else:

diff --git a/lib/matplotlib/backends/web_backend/nbagg_mpl.js b/lib/matplotlib/backends/web_backend/nbagg_mpl.js
@@ -55,15 +55,21 @@ mpl.mpl_figure_comm = function(comm, msg) {
 };

 mpl.figure.prototype.handle_close = function(fig, msg) {
+    fig.root.unbind('remove')
+
    // Update the output cell to use the data from the current canvas.
    fig.push_to_output();
    var dataURL = fig.canvas.toDataURL();
    // Re-enable the keyboard manager in IPython - without this line, in FF,
    // the notebook keyboard shortcuts fail.
    IPython.keyboard_manager.enable()
    $(fig.parent_element).html('<img src="' + dataURL + '">');
-    fig.send_message('closing', {});
-    fig.ws.close()
+    fig.close_ws(fig, msg);
+}
+
+mpl.figure.prototype.close_ws = function(fig, msg){
+    fig.send_message('closing', msg);
+    // fig.ws.close()
 }

 mpl.figure.prototype.push_to_output = function(remove_interactive) {
@@ -126,6 +132,12 @@ mpl.figure.prototype._init_toolbar = function() {
    titlebar.prepend(buttongrp);
 }

+mpl.figure.prototype._root_extra_style = function(el){
+    var fig = this
+    el.on("remove", function(){
+	fig.close_ws(fig, {});
+    });
+}

 mpl.figure.prototype._canvas_extra_style = function(el){
    // this is important to make the div 'focusable