How to extend painting of a control.

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Hi,
I want to add tick labels to a trackbar control. Each tick has a label underneath it.
Therefore I do the following :

public DateTimeTrackBar()
{
    :
    SetStyle(ControlStyles.UserPaint  | ControlStyles.ResizeRedraw, true);
}

protected override void OnPaintBackground(PaintEventArgs e)
{
    base.OnPaintBackground(e);

    if (ShowLabels)
        DrawLabels(e);
}

The label drawing works fine, except that the original trackbar disappears.
How can i keep the original trackbar drawing and extend it with my label drawing code ?

tia

Posted 23-Jan-16 5:40am

Ronny Portier

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Sergey Alexandrovich Kryukov · Answer 1 · 2016-01-23T05:50:00

Instead of OnPaintBackground (its purpose is different), override OnPaint:
Control.OnPaint Method (PaintEventArgs) (System.Windows.Forms)[^].

Alternatively, you can handle the corresponding event System.Windows.Drawing.Control.Paint. But you don't need it because you are writing derived class anyway, so overriding is not a problem. By the way, if you override the method, don't handle this event (you could do it both, but usually it's poinless) and don't want the users to handle this event, don't call base.Paint.

—SA