Pixmap graphics ports are drawing destinations which exist only as pixel arrays whose contents are not directly accessible. They can be drawn to using the
draw-
thing
functions, and their contents can be copied onto other graphics ports. However this copying can be meaningless unless the conversion of colors uses the same color device on both ports. Because color devices are associated with regular graphics ports (Windows) rather than pixmap graphics ports, you have to connect a pixmap graphics port to a regular graphics port for color conversion. This is the purpose of the
owner
slot in
pixmap-graphics-port-mixin
. The conversion of colors to pixel values is done in the same way as for regular graphics ports, but the pixmap graphics port's owner is used to find a color device. You can draw to pixmap graphics ports using pre-converted colors to avoid color conversion altogether, in which case a null color owner is OK for a pixmap graphics port.