Inside Macintosh: QuickDraw GX Objects /

Chapter 2 - Shape Objects / Shape Objects Reference

Constants and Data Types

The Hit-Test Info Structure

The hit-test info structure is a structure in which both the GXHitTestShape and GXHitTestPicture functions return information. GXHitTestShape uses only
the first three fields; GXHitTestPicture uses all seven fields.

struct gxHitTestInfo {
   gxShapePart    what;
   long           index;
   Fixed          distance;
   gxShape        which;
   gxShape        containerPicture;
   long           containerIndex;
   long           totalIndex;
};

Field Description

what

The parts of the shape that were hit, if any. QuickDraw GX returns in this field a mask denoting all shape parts (out of those specified for the hit-test) that are within the tolerance of the hit-test from
the hit point. Shape parts are defined in the gxShapeParts enumeration; the tolerance and the subset of shape parts to test for make up the hit-test parameters. All are described in the chapter "Transform Objects" in this book.

index

The index of the nearest point in the geometry to the hit point. Every point in a shape's geometry has an index number (indexes start at 1).

distance

The distance in geometry units from the hit point to the closest point on the shape part that was hit. (If no part was hit, this value is undefined.) If more than one shape part was hit, this is the distance to the first shape part encountered that is within the tolerance of the hit point. The order in which shape parts are examined during hit-testing is defined by the gxShapeParts enumeration, described in the chapter "Transform Objects" in this book.

which

A reference to the specific shape that was hit. (Used only by GXHitTestPicture.)

containerPicture

A reference to the picture shape that immediately contains the specific shape that was hit. Note that this may be a picture shape contained at some level within the picture shape specified in the call to GXHitTestPicture. (Used only by GXHitTestPicture.)

containerIndex

The index number--within the immediately containing shape--of the specific shape that was hit. (Used only by GXHitTestPicture.)

totalIndex

The index number--within the picture shape specified in the call to GXHitTestPicture--of the specific shape that was hit. (Used only by GXHitTestPicture.)

The GXHitTestShape function is described on page 2-86. The GXHitTestPicture function is described in the picture shapes chapter of Inside Macintosh: QuickDraw GX Graphics.