How to maintain a scroll bar position after updating textctrl content?

wxPython Users
#1

Hi, mates, I am struggling to maintain a scroll bar position after updating textctrl content. Let me show my code firstly:

class MyFrame(rtmgr.MyFrame):
    def __init__(self, *args, **kwds):
        rtmgr.MyFrame.__init__(self, *args, **kwds)
        self.scroll_pos = 0
    
    def updateCtrlMsg(self, msg):
        self.scroll_pos = self.text_ctrl_1.GetScrollPos(wx.VERTICAL)
        self.text_ctrl_1.SetValue(msg)
        self.text_ctrl_1.SetScrollPos(wx.VERTICAL ,self.scroll_pos)

class MyApp(wx.App):
    def OnInit(self):
        self.frame = MyFrame(None, wx.ID_ANY, "")
        self.SetTopWindow(self.frame)
        self.frame.Show()
        return True

def main(args=None):
    
    app = MyApp(0)

    # Start wxPython main loop
    app.MainLoop()
  

if __name__ == '__main__':
    main()

In another thread, I use wx.CallAfter(self.app.frame.updateCtrlMsg, data) to update the content of textctrl.

but one thing confuses me a lot, why the scroll bar of textctrl automatically reset to the top all the time even though i have scrolled down.

could anyone give some suggestions to me to fix it out?

the following gif shows the problems:

scrollbar 00_00_00-00_00_30
scrollbar 00_00_00-00_00_30640×536 2.33 MB

#2

Hi,

I modified your code to get a runnable app. Instead of using a separate thread to update the TextCtrl my code just uses a timer to call a function to get some random data.

When I used self.text_ctrl_1.SetScrollPos(wx.VERTICAL, self.scroll_pos) in the updateCtrlMsg() I got the same behaviour as you - the scrollbar kept jumping back to the top.

However, when I replaced that line with self.text_ctrl_1.ShowPosition(self.scroll_pos) the scrollbar didn’t jump.

import wx
from random import randint

def getMsg():
    msg = ''
    for i in range(20):
        msg += f"Line {i}: {randint(0, 9)}\n"
    return msg


class MyFrame(wx.Frame):
    def __init__(self, *args, **kwds):
        wx.Frame.__init__(self, *args, **kwds)
        sizer = wx.BoxSizer(wx.VERTICAL)
        self.text_ctrl_1 = wx.TextCtrl(self, -1, '', style=wx.TE_MULTILINE)
        sizer.Add(self.text_ctrl_1, 1, wx.EXPAND, 0)
        self.SetSizer(sizer)
        self.scroll_pos = 0

        self.timer = wx.Timer(self)
        self.Bind(wx.EVT_TIMER, self.OnTimer)
        self.timer.Start(1000)

    def OnTimer(self, _event):
        msg = getMsg()
        self.updateCtrlMsg(msg)

    def updateCtrlMsg(self, msg):
        self.scroll_pos = self.text_ctrl_1.GetScrollPos(wx.VERTICAL)
        self.text_ctrl_1.SetValue(msg)
        # self.text_ctrl_1.SetScrollPos(wx.VERTICAL, self.scroll_pos)
        self.text_ctrl_1.ShowPosition(self.scroll_pos)


class MyApp(wx.App):
    def OnInit(self):
        self.frame = MyFrame(None, wx.ID_ANY, "")
        self.SetTopWindow(self.frame)
        self.frame.Show()
        return True


def main():
    app = MyApp(0)
    app.MainLoop()


if __name__ == '__main__':
    main()

I don’t know why it behaves differently.

I am using wxPython 4.2.1 gtk3 (phoenix) wxWidgets 3.2.4 + Python 3.12.3 + Linux Mint 22

#3

it’s nice try to use ShowPostion API and I will do it later. Thanks for your great support. But still I would keep focusing on why it behaves differently. Highly appreciate if anyone would share their ideas.

#4

wx.TextCtrl inherits the SetScrollPos() method from its wx.Window ancestor class. In the documentation for the method it says:

Note: This function does not directly affect the contents of the window: it is up to the application to take note of scrollbar attributes and redraw contents accordingly.