modal dialog that freezes the whole desktop

wxPython Users
1

Hello everybody,

I use wxpython 2.8.12.1 altogether with matplotlib backend (1.1.1rc) on an ubuntu machine (12.04). I
would like to connect my matplotlib canvas to a button_press_event that
pops up a wxpython message dialog (modal). When the modal dialog pops up, the whole application gets frozen BUT also the message dialog on which I do not have any control anymore AND the desktop on which the application is currently running. The only way to escape from this, is to switch desktop using keyboard and come back to the one that contains the application. This problem does not occur on a windows machine. Here is a code snippet that typically reproduces the problem.

···

##################################################

import wx

from matplotlib.backends.backend_wxagg import FigureCanvasWxAgg
from matplotlib.figure import Figure

class PlotterFrame(wx.Frame):

def __init__(self, parent, title="Frame with matplotlib canvas"):
   
    wx.Frame.__init__(self, parent, wx.ID_ANY, title)
                                           
    self.figure = Figure(figsize=(5,4), dpi=None)
    self.canvas = FigureCanvasWxAgg(self, -1, self.figure )
    self.canvas.mpl_connect("button_press_event", self.on_click)

def on_click(self, event=None):
     d = wx.MessageDialog(self, message = "I

am Mr freeze")
d.ShowModal()
d.Destroy()

if name == “main”:
app = wx.App(False)
f = PlotterFrame(None)
f.Show()
app.MainLoop()

####################################################################

This problem does not occur with a “pure” wxpython application with no matpotlib
backend.

Am I doing something wrong or is it a bug in the matplotlib backend ?

thank you very much for your help

Eric

2

Pellegrini Eric wrote:

Hello everybody,

I use wxpython 2.8.12.1 altogether with matplotlib backend (1.1.1rc) on
an ubuntu machine (12.04). I would like to connect my matplotlib canvas
to a button_press_event that pops up a wxpython message dialog (modal).
When the modal dialog pops up, the whole application gets frozen BUT
also the message dialog on which I do not have any control anymore AND
the desktop on which the application is currently running. The only way
to escape from this, is to switch desktop using keyboard and come back
to the one that contains the application. This problem does not occur on
a windows machine. Here is a code snippet that typically reproduces the
problem.

I don't know if this is the same issue but one thing I ran into when using MPL is that if certain modules get imported before there is an app object then it will create its own, and if the default backend is set to something other than wx then it could be importing and creating an app object for some other gui toolkit and that could be what is messing up the dialog's modal event loop.

Matplotlib has a mechanism for selecting which back-end should be used, and with some careful importing you can ensure that it doesn't create its own wx.App instance. I dealt with that simply by having my wx.App and main frame classes in a module that does not import any matplotlib modules. Once the app and the frame were created then I imported the module that implemented my plot canvas classes and then matplotlib was imported from there.

···

--
Robin Dunn
Software Craftsman