c# - Disabling RichTextBox autoscroll

Question

I am using RichTextBox control for displaying application logs. I am updating control once a second with a few calls of RichTextBox::AppendText method. What is really annoying for me is that cursor keeps scrolling to the last line of text. Its very uncomfortable in situation when user needs to analyze logs that are at the beginning. I have tried following solution to my problem:

int pos = tb_logs.SelectionStart;
tb_logs.AppendText("log message");
tb_logs.SelectionStart = pos;

This does not go to the core of problem because control is being periodically redrawed which is very distracting. Is there some cleaner solution?

Answer 1

If your issue is with the "Vertical Scroll" scrolling down when you are adding the Log text, but you would want it to be on top all the time:

you have to add event handlers to VScroll, TextChanged events and in the event handler set the scroll to top

richTextBox1.VScroll += HandleRichTextBoxAdjustScroll;
richTextBox1.TextChanged += HandleRichTextBoxAdjustScroll;

private const UInt32 SB_TOP = 0x6;
private const UInt32 WM_VSCROLL = 0x115;

[return: MarshalAs(UnmanagedType.Bool)]
[DllImport("user32.dll", SetLastError = true)]
private static extern bool PostMessage(IntPtr hWnd, UInt32 Msg,
    IntPtr wParam, IntPtr lParam);

private void HandleRichTextBoxAdjustScroll(Object sender,
    EventArgs e)
{
    PostMessage(handle, WM_VSCROLL, (IntPtr)SB_TOP, IntPtr.Zero);
}

You could do the same with horizontal scroll bar too. Replace WM_VSCROLL with WM_HSCROLL and SB_TOP with SB_LEFT

private const UInt32 WM_HSCROLL = 0x0114;
private const UInt32 SB_LEFT = 0x06;