TreeView flickering

• .NET Core Version: all up to latest (5.0.5).

• Have you experienced this same bug with .NET Framework?: yes

Problem description: TreeView is flickering (especially on large amount of data): Native control has ex. style TVS_EX_DOUBLEBUFFER that fix the problem:

private class TreeViewEx : TreeView
{
    private const int TVM_SETEXTENDEDSTYLE = 0x1100 + 44;
    private const int TVS_EX_DOUBLEBUFFER = 0x0004;

    [System.Runtime.InteropServices.DllImport("user32.dll", SetLastError = true)]
    private static extern IntPtr SendMessage(IntPtr HWnd, int Msg, IntPtr Wp, IntPtr Lp);

    protected override void OnHandleCreated(EventArgs e)
    {
        SendMessage(this.Handle, TVM_SETEXTENDEDSTYLE, (IntPtr)TVS_EX_DOUBLEBUFFER, (IntPtr)TVS_EX_DOUBLEBUFFER);
        base.OnHandleCreated(e);
    }
}

Left default TreeView, Right with TVS_EX_DOUBLEBUFFER: stackoverflow.

Expected behavior: Ability to avoid flickering without Pinvoke and deriving own class from TreeView. P.s. protected DoubleBuffered doesn’t solve the problem. P.p.s. May be API request is more suitable here?

Minimal repro: TreeViewFlickering.zip

[KlausLoeffelmann]

A proposal it is.

[RussKie]

According to the docs DoubleBuffered=true makes no difference, though this would be the first thing I’d try. Perhaps this is something we could consider enhancing. @merriemcgaw @KlausLoeffelmann what do you think?

Also interestingly enough we have this method: https://github.com/dotnet/winforms/blob/d46ad2e8dc76248739d9ae22b28b399a6a6b299e/src/System.Windows.Forms.Design/src/System/Windows/Forms/Design/DesignerUtils.cs#L878-L892