/// <summary>
/// Event handling for horizontal scroll bar. The image part will
/// be adapted according to the position of horizontal scroll bar.
/// </summary>
private void hScrollBar1_Scroll(object sender, ScrollEventArgs e)
{
Rectangle rect = viewPort.ImagePart;
rect.X = hScrollBar1.Value;
hWndControl.setImagePart(rect.Y, rect.X,
rect.Y + rect.Height,
rect.X + rect.Width);
hWndControl.repaint();
}