All Manuals > CAPI User Guide > 13 Graphics Ports > 13.6 Combining source and target pixels


13.6.1 Combining pixels with :compatible drawing

When the port's drawing-mode is :compatible the graphics state parameter operation determines how the colors are combined, and compositing-mode is ignored

The allowed values of operation are the values of the Common Lisp constants boole-1 , boole-and and so on. These are the allowed values of the first argument to the Common Lisp function boole. See the specification of boole in the ANSI Common Lisp standard for the full list of operations.

The color combination corresponds to the logical operation defined there, as if by calling

(boole operation new-pixel screen-pixel )

For example, passing :operation boole-andc2 provides a graphics state where graphics ports drawing functions draw with the bitwise AND of the foreground color and the complement of the existing color of each pixel.

Note: Graphics State operation is not supported by Cocoa/Core Graphics so this parameter is ignored on Cocoa.

CAPI User Guide (Unix version) - 30 Aug 2011