Sets the pen stipple bitmap. The stipple is only used when the brush's style is wx:const-stipple or wx:const-opaque-stipple (see also set-style), but setting the bitmap to null turns off the stipple bitmap. A bitmap cannot be used as a stipple if it is selected into a wx:memory-dc% object.
A pen cannot be modified if it was obtained from a wx:pen-list% or while it is selected into a drawing context.