I have added my own handlers to manage tool tips on a TreeView, setup code:

this.TreeViewSites.NodeMouseHover += TreeViewSites_NodeMouseHover;
this.ToolTip1.Draw += ToolTip1_Draw;
this.ToolTip1.OwnerDraw = true;

The handlers:

private void TreeViewSites_NodeMouseHover(object sender, TreeNodeMouseHoverEventArgs e) {
    if (!string.IsNullOrEmpty(e.Node.ToolTipText)) {
        ToolTip1.Show(e.Node.ToolTipText, TreeViewSites);
    }
}
        
private void ToolTip1_Draw(object sender, DrawToolTipEventArgs e) {
    using (StringFormat sf = new StringFormat()) {
        sf.Alignment = StringAlignment.Center;
        sf.LineAlignment = StringAlignment.Near;
        sf.HotkeyPrefix = System.Drawing.Text.HotkeyPrefix.None;
        sf.FormatFlags = StringFormatFlags.NoWrap;
        using (Font f = new Font("Courier New", 10)) {
            e.Graphics.DrawString(e.ToolTipText, f
                                , SystemBrushes.ActiveCaptionText
                                , e.Bounds, sf);
        }
    }
}

For some reason unknown to me, when the tool tips are displayed I’m seeing a solid black rectangle???