TextCtrl disappears after changing color and calling sizer.Layout

Question

I have encountered a very strange problem in wxPython which I think is a bug. Essentially I have one TextCtrl which changes background color when I press the ctrl key (don't ask why). I then have another button that calls sizer.Layout() on the BoxSizer where the TextCtrl is stored. When I do this, the TextCtrl disappears (attains a zero width). It only happens if there is sufficient text in the TextCtrl, and only if I press ctrl+(other key). Here is the code:

import wx


class MyPanel(wx.Panel):


    def __init__(self, parent):
        wx.Panel.__init__(self, parent)
        self.frame = parent


        self.sizer = wx.BoxSizer(wx.VERTICAL)



        self.btn = wx.Button(self, label="TextCtrl disappears?")
        self.btn.Bind(wx.EVT_BUTTON, self.onClick)

        self.txt=wx.TextCtrl(self,value="bunch of text goes here")
        self.txt.Bind(wx.EVT_KEY_DOWN, self.onType)

        self.sizer.Add(self.txt,0,wx.CENTER|wx.ALL,5)
        self.sizer.Add(self.btn,0,wx.CENTER|wx.ALL,5)
        self.SetSizer(self.sizer)
        self.Fit()  


    def onType(self,event):
        if event.GetKeyCode()==308:
            self.txt.SetBackgroundColour((100,255,255,255))
        else:
            event.Skip()



    def onClick(self,event):

        self.sizer.Layout()

class MyFrame(wx.Frame):

    def __init__(self):
        wx.Frame.__init__(self, parent=None, title="")
        panel = MyPanel(self)

        self.Fit()
        self.Show()


app = wx.App(False)
frame = MyFrame()

app.MainLoop()

Now, try to go to the TextCtrl and press for instance ctrl+a, and then press the button. Is this a bug? More importantly, what is the workaround? I guess that the TextCtrl changes one of its attributes that specifies its size or behaviour under Layout(), but I can not figure out which one is being changed.

edit:

I am using ubuntu 16.04, Python 2.7.12 and wxpython version 3.0.2.0.

Answer 1

Whatever it is, it has been resolved in wxpython 4.
Ways to avoid the problem.

Give the TextCtrl a size=(n,n) value

and / or

Replace the wx.CENTER with a wx.EXPAND when adding to the sizer.

i.e.

self.txt=wx.TextCtrl(self,-1,value="bunch of text goes here",size=(50,20))

self.sizer.Add(self.txt,0,wx.EXPAND|wx.ALL,5)

Finally, there must be something queer about your keyboard, because this should not happen using EVT_KEY_DOWN but with EVT_KEY_UP. I don't think that EVT_KEY_DOWN normally sees a Ctrl key. See https://www.wxpython.org/Phoenix/docs/html/wx.KeyEvent.html