Extending Shapes and Sets

The QuickDraw 3D shape and set routines are discussed in "Managing Shapes" .

The Q3Shape_GetSet and Q3ShapeSetSet calls are implemented via the element type kQ3ElementTypeSet :

typedef long    TQ3ElementType;
#define kQ3ElementTypeNone      0
#define kQ3ElementTypeUnknown   32
#define kQ3ElementTypeSet       33
#define kQ3ElementTypeName      34
#define kQ3ElementTypeURL       35


The expression Q3Shape_GetSet(s,&o) is eqivalent to

Q3Shape_GetElement(s, kQ3ElementTypeSet, &o)

The expression Q3Shape_SetSet(s,o) is eqivalent to

Q3Shape_SetElement(s, kQ3ElementTypeSet, &o)

It is important to note that a Q3Shape_ ... Element ... call does not create a set on a shape and then add the element to it. The data is attached directly to the shape. Therefore, it is possible for an element to exist on a shape without a set existing on it as well.

In your application, if you attach an element to a shape in this way:

set = Q3Set_New();
Q3Set_AddElement(set, ElemType, &data);
Q3Shape_SetSet(shape, set);


You should retrieve it in the same manner:

Q3Shape_GetSet(shape, &set);
if (Q3Set_Contains(set, ElemType) == kQ3True) {
    Q3Set_Get(set, ElemType, &data);
}


Similarly, if you attach data to a shape with the call

Q3Shape_AddElement(shape, ElemType, &data);


You should retrieve it in the same manner:

if (Q3Shape_ContainsElement(
    set, ElemType) == kQ3True) {
    Q3Shape_GetElement(set, ElemType, &data);
}


When attempting to find a particular element on a shape, you should first check with Q3Shape_GetNextElementType or Q3Shape_GetElement . Then you should call

Q3Shape_GetSet(s, &set) or

Q3Shape_GetElement(s, kQ3ElementTypeSet, &set)) .

Finally, you should call Q3Shape_GetElement(set, ...) .

In terms of implementation, Q3Shape_SetSet and Q3Shape_GetSet should be used only for sets of information that are shared among multiple shapes. Q3Shape_AddElement , Q3Shape_GetElement , and similar calls should be used only for elements that are unique to a particular shape.

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© 1997 Apple Computer, Inc.

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