Inside Macintosh: QuickDraw GX Objects /

Chapter 6 - Transform Objects / Transform Objects Reference

Functions / Performing Geometric Operations on Transform Clips

GXReverseDifferenceTransform

You can use the GXReverseDifferenceTransform function to subtract the geometry of the clip shape in a transform object from the geometry of a specified shape object, and then replace the transform's clip property with the resulting geometry.

void GXReverseDifferenceTransform(gxTransform target, 
                                    gxShape operand);

target

A reference to the transform object containing the clip property you want to modify.

operand

A reference to the shape containing the geometry from which you want to subtract the target transform's clip.

ERRORS, WARNINGS, AND NOTICES

Errors
out_of_memory
transform_is_nil
shape_is_nil
number_of_contours_exceeds_implementation_limit
number_of_points_exceeds_implementation_limit
size_of_path_exceeds_implementation_limit
size_of_polygon_exceeds_implementation_limit
shapeFill_not_allowed	(debugging version)
shape_access_not_allowed	(debugging version)
clip_to_frame_shape_unimplemented	(debugging version)
shape_may_not_be_a_bitmap	(debugging version)
shape_may_not_be_a_picture	(debugging version)
Warnings
character_substitution_took_place
unable_to_traverse_open_contour_that_starts_or_ends_off_the_curve
	(debugging version)

SEE ALSO

For an illustration of the effects of the GXReverseDifferenceTransform function on the transform clip, see Figure 6-8 on page 6-22. For a general description of constructive geometry operations, see the geometric operations chapter of Inside Macintosh: QuickDraw GX Graphics.