I'm putting some lines in a list control and then updating them fairly quickly - normally the data comes in from a bus - and the whole list flickers quite a lot. It would be really nice to stop it doing that.
I've cut down the code as much as I can while still keeping the general look of what I'm doing in the sample below.
It doesn't seem to matter if the lisctrl is in a wx.Notebook or just a plain wx.Panel so I left the notebook there.
I've started to look at double buffering but wanted to see if there was something else to try first.
Doing this on Windows 7 with wxPython 2.8.12.1. Happens on XP as well though.
import sys
import time
import logging
import wx
from random import randint
UPDATE_MS=10
class CanMsg(object):
def __init__(self, ID, type, len, data=None):
"""Represents a CAN message"""
self.ID=ID # 11/29-bit message identifier
self.MSGTYPE=type # Type of the message
self.LEN=len # Data Length Code of the message (0..8)
if data:
self.DATA=data
else:
self.DATA=[0,]*len
class EmulatorFrame(wx.Frame):
def __init__(self, parent, id, title, pos=wx.DefaultPosition, size=wx.DefaultSize,
style=wx.DEFAULT_FRAME_STYLE):
wx.Frame.__init__(self, parent, id, title, pos, size, style)
# create frame menu and status bar
self.status = self.CreateStatusBar()
# create tab panels
panel = wx.Panel(self)
nb = wx.Notebook(panel)
self.messages_tab = MessagesTab(nb)
# self.messages_tab = MessagesTab(panel)
# add tab pages to notebook
nb.AddPage(self.messages_tab, 'CAN data')
self._nb = nb
sizer = wx.BoxSizer()
sizer.Add(nb, 1, wx.EXPAND)
# sizer.Add(self.messages_tab, 1, wx.EXPAND)
minSize=self.ClientToWindowSize(sizer.GetMinSize()) # get this as Info tab's min size is too small
panel.SetSizerAndFit(sizer)
self.SetInitialSize(minSize)
self.InitialiseTimers()
def InitialiseTimers(self):
# tab updates and test comparison timer
self.displayTimer=wx.Timer(self)
self.Bind(wx.EVT_TIMER, self.OnRefresh, self.displayTimer)
self.displayTimer.Start(UPDATE_MS)
# self.Bind(wx.EVT_IDLE, self.OnRefresh)
def OnRefresh(self, event):
self.messages_tab.Update(can_send, can_recv)
class MessagesTab(wx.Panel):
def __init__(self, parent):
msg_size=450 # width of messge windows
wx.Panel.__init__(self, parent, wx.ID_ANY)
receivedLabel=wx.StaticText(self, wx.ID_ANY, 'Messages Received')
receivedLabel.SetForegroundColour('blue')
sentLabel=wx.StaticText(self, wx.ID_ANY, 'Messages Sent')
sentLabel.SetForegroundColour('dark slate blue')
SentMsgList = MessageList(self, size=wx.Size(msg_size,150))
ReceivedMsgList = MessageList(self, size=wx.Size(msg_size,150))
sizer=wx.BoxSizer(wx.VERTICAL)
sizer.Add(sentLabel, 0, wx.EXPAND|wx.ALL, 2)
sizer.Add(SentMsgList, 1, wx.EXPAND|wx.ALL, 2)
sizer.Add(receivedLabel, 0, wx.EXPAND|wx.ALL, 2)
sizer.Add(ReceivedMsgList, 1, wx.EXPAND|wx.ALL, 2)
b = wx.Button(self, wx.ID_ANY, 'Clear messages', name='clear_stale')
self.Bind(wx.EVT_BUTTON, self.OnClearMessages, b)
sizer.Add(b, proportion=0, flag=wx.ALL, border=4)
self.SetSizer(sizer)
self.SentMsgList = SentMsgList
self.ReceivedMsgList = ReceivedMsgList
def Update(self, can_send, can_recv):
self.SentMsgList.Populate(can_send)
self.ReceivedMsgList.Populate(can_recv)
def OnClearMessages(self, event):
self.SentMsgList.DeleteAllItems()
self.ReceivedMsgList.DeleteAllItems()
class MessageList(wx.ListCtrl):
def __init__(self, parent, ID=wx.ID_ANY, pos=wx.DefaultPosition,
size=wx.DefaultSize, style=wx.LC_REPORT|wx.LC_HRULES|wx.LC_VRULES|wx.LC_SORT_ASCENDING):
wx.ListCtrl.__init__(self, parent, ID, pos, size, style)
self.InsertColumn(0, "COB-ID")
self.InsertColumn(1, "Type")
self.InsertColumn(2, "Len")
self.InsertColumn(3, "Data")
self.InsertColumn(4, "Cycle [ms]")
self.SetColumnWidth(0, 60)
self.SetColumnWidth(1, 40)
self.SetColumnWidth(2, 40)
self.SetColumnWidth(3, 200)
self.SetColumnWidth(4, 75)
# either add messages to the listctrl or update the existing ones if
def Populate(self, msg_store):
item=-1
while 1:
item = self.GetNextItem(item, wx.LIST_NEXT_ALL, wx.LIST_STATE_DONTCARE)
if item == -1: break
if self.GetItemText(item) not in msg_store:
self.DeleteItem(item)
for msg_id in msg_store:
item = self.FindItem(-1, msg_id)
msg = msg_store.get(msg_id)
interval = randint(10,1000)
# insert new messages
if item == -1:
item = self.InsertStringItem(sys.maxint, msg_id)
self.SetStringItem(item, 1, 'std')
# fill in other columns
self.SetStringItem(item, 2, '%1d'%msg.LEN)
self.SetStringItem(item, 3, ' '.join(['%02x'%d for d in msg.DATA[:msg.LEN]]))
self.SetStringItem(item, 4, '%d'%interval)
#====================================================================
#====================================================================
if __name__=='__main__':
msg=(0x180, 0, 8, range(1,9))
can_send={}
can_recv={}
# just make up some simple messages for listctrl to display
# send msgs
for a in range(1,7):
this_msg=list(msg)
this_msg[0] += a
can_send[hex(this_msg[0])] = CanMsg(*msg)
# receive msgs
for a in range(1,10):
this_msg=list(msg)
this_msg[0] += 0x100+a
can_recv[hex(this_msg[0])] = CanMsg(*msg)
app=wx.App(0) # 0 arg stops stdout/stderr text box pop-up, messages go to console
frame = EmulatorFrame(None, wx.ID_ANY, 'Listctrl flicker test')
frame.Show(True)
app.MainLoop()
Ok I think I finally have a workable (if partial) answer the flicker problem.
I found a number of people had success, mostly with image flickering, by enabling double buffering on the panel. So in the MessagesTab() class, after the wx.Panel init, I inserted the line;
self.SetDoubleBuffered(True)
This made the list control updates smooth but resizing the GUI or mousing over the listctrl column headers would make the contents flicker a lot or disappear entirely. Being Windows 7 the header highlights as per the OS theme when the mouse is on it. Since this seemed to be the cause my workaround was to add the wx.LC_NO_HEADER flag to the MessageList() style arg. So the listctrl has no header but nothing causes flicker or vanishing text now and I can replace it with some static text. Resizing is no problem either.
So maybe there's some problem with events generated on the column headers?