Page 120	Table of Contents	Index	Page 122
	Chapters
	1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 A, B, C, D, E

CHAPTER 13. DRAWING IN COLOR

change the color in the background that would have been drawn by design1 at that point into
the color that would have been drawn by design2 at that point, and vice versa. The effect on
any color other than the colors determined by those two designs is unspecified; however, drawing
the same figure twice using the same flipping ink is guaranteed to be an "identity" operation. If
either design1 or design2 is not solid, the consequences are unspecified. The purpose of flipping
is to allow the use of "XOR hacks" for temporary changes to the display.

The opacity of a flipping ink is zero at points where the opacity of either design1 or design2
is zero. Otherwise the opacity of a flipping ink is 1. If design1 or design2 is translucent, the
consequences are unspecified. If compose-in or compose-out is used to make a flipping ink
translucent, the consequences are unspecified.

If design1 and design2 are equivalent, the result can be +nowhere+.

In Release 2, make-flipping-ink might require design1 and design2 to be colors.

=> +flipping-ink+ [Constant]
A flipping ink that flips +foreground-ink+ and +background-ink+.

13.8 Examples of Simple Drawing Effects

Drawing in the foreground color. Use the default, or specify :ink +foreground-ink+.

Erasing. Specify :ink +background-ink+.

Drawing in color. Specify :ink +green+, :ink (make-rgb-color 0.6 0.0 0.4), and so
forth.

Drawing an opaque gray. Specify :ink (make-gray-color 0.25) to draw in a shade of
gray independent of the window's foreground color. On a non-color, non-grayscale display this
will generally turn into a stipple.

Page 120	Table of Contents	Index	Page 122
	Chapters
	1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 A, B, C, D, E