The new graphics state parameter compositing-mode controls the way that new drawings are combined with the existing value in the target of the drawing to generate the result.
Two values for compositing-mode are supported on Microsoft Windows, Cocoa and GTK+.
:over
means draw over the existing values, blending alpha values if they exist.
:copy
means that the source is written to the destination ignoring the existing values. If the source has alpha and the target does not, that has the effect of converting semi-transparent source to solid.
:copy
is especially useful for creating transparent and semi-transparent pixmap ports, which can be displayed directly or converted to images by
gp:make-image-from-port
.A number of other compositing-mode values are supported on later versions of Cocoa and GTK+.
compositing-mode
is only supported in with
drawing-mode
:quality
.
For further details and examples see the manual page for
gp:graphics-state
.
LispWorks Release Notes and Installation Guide - 23 Dec 2011