Sets the background mode.
Specifies the mode to be set. This parameter can be either of the following values:
OPAQUE Background is filled with the current background color before the text, hatched brush, or pen is drawn. This is the default background mode.
TRANSPARENT Background is not changed before drawing.
The previous background mode.
The background mode defines whether the system removes existing background colors on the drawing surface before drawing text, hatched brushes, or any pen style that is not a solid line.