Error in WebAgg When "S" Key is Pressed

[blink1073]

I am using IPython 2.3.1 and ab549ac. To reproduce, run IPython and %paste the code below. Click on the figure and then press the 'S' key. The traceback below is printed and the figure becomes unresponsive.

import matplotlib
import itertools
import numpy as np
matplotlib.use('webagg')
import matplotlib.pyplot as plt
plt.close('all')
fig, ax = plt.subplots()
x = np.linspace(0,10,10000)
y = np.sin(x)
ln, = ax.plot(x,y)
evt = []
colors = iter(itertools.cycle(['r', 'g', 'b', 'k', 'c']))
def on_event(event):
    evt.append(event)
    ln.set_color(next(colors))
    fig.canvas.draw()
    fig.canvas.draw_idle()
fig.canvas.mpl_connect('button_press_event', on_event)
plt.show()

ERROR:tornado.application:Uncaught exception in /1/ws
Traceback (most recent call last):
  File "/home/silvester/anaconda/lib/python3.4/site-packages/tornado/websocket.py", line 369, in _run_callback
    callback(*args, **kwargs)
  File "/home/silvester/workspace/matplotlib/lib/matplotlib/backends/backend_webagg.py", line 230, in on_message
    manager.handle_json(message)
  File "/home/silvester/workspace/matplotlib/lib/matplotlib/backends/backend_webagg_core.py", line 361, in handle_json
    self.canvas.handle_event(content)
  File "/home/silvester/workspace/matplotlib/lib/matplotlib/backends/backend_webagg_core.py", line 219, in handle_event
    self.key_press_event(key)
  File "/home/silvester/workspace/matplotlib/lib/matplotlib/backend_bases.py", line 1837, in key_press_event
    self.callbacks.process(s, event)
  File "/home/silvester/workspace/matplotlib/lib/matplotlib/cbook.py", line 534, in process
    proxy(*args, **kwargs)
  File "/home/silvester/workspace/matplotlib/lib/matplotlib/cbook.py", line 415, in __call__
    return mtd(*args, **kwargs)
  File "/home/silvester/workspace/matplotlib/lib/matplotlib/backend_bases.py", line 2597, in key_press
    key_press_handler(event, self.canvas, self.canvas.toolbar)
  File "/home/silvester/workspace/matplotlib/lib/matplotlib/backend_bases.py", line 2490, in key_press_handler
    toolbar.save_figure()
  File "/home/silvester/workspace/matplotlib/lib/matplotlib/backend_bases.py", line 3155, in save_figure
    raise NotImplementedError
NotImplementedError

[blink1073]

I'd vote in favor of raising a warning here instead of crashing the app.

[blink1073]

Specifically:

diff --git a/lib/matplotlib/backends/backend_webagg_core.py b/lib/matplotlib/backends/backend_webagg_core.py
index ceb43ba..da3b994 100644
--- a/lib/matplotlib/backends/backend_webagg_core.py
+++ b/lib/matplotlib/backends/backend_webagg_core.py
@@ -19,6 +19,7 @@ import io
 import json
 import os
 import time
+import warnings

 import numpy as np

@@ -318,6 +319,10 @@ class NavigationToolbar2WebAgg(backend_bases.NavigationToolbar2):
         self.canvas.send_event(
             "rubberband", x0=-1, y0=-1, x1=-1, y1=-1)

+    def save_figure(self, *args):
+        """Save the current figure"""
+        warnings.warn('Save figure not implemented in Web Backend')
+

 class FigureManagerWebAgg(backend_bases.FigureManagerBase):
     ToolbarCls = NavigationToolbar2WebAgg

[pelson]

👍

On the super wish list - I'd love to have a little console on the webagg/nbagg interface which allowed us to propagate warnings to the user directly in the browser.

[blink1073]

FYI I got a gittip for this. Ugh....

[blink1073]

Well prime4commit to be precise.

[tacaswell]

I think the projects position is to just ignore them. I also dug into it a while ago and I think it is worth some comically small amount in $ terms and no one hand actually claimed any mpl related coins yet.

I think I marked the one I got as spam to try and train google to suppress it.