The Join Structure (IM: XG)

Inside Macintosh: QuickDraw GX Graphics /

Chapter 3 - Geometric Styles / Geometric Styles Reference

The Join Structure
QuickDraw GX allows you to specify a join shape to be drawn at the corners of another shape's contours. In particular, you may specify a join shape for any rectangle, polygon, or path shape that has an open-frame shape fill or a closed-frame shape fill.

For shapes with the closed-frame shape fill, QuickDraw GX draws the specified join shape at every on-curve geometric point of each contour.
For shapes with the open-frame shape fill, QuickDraw GX draws the specified join shape at every on-curve geometric point between the first point and the last point of each contour.

QuickDraw GX uses the join property of a shape's style object to store information about the join of the shape.
You use the join structure when specifying join information (using the GXSetStyleJoin or GXSetShapeJoin functions) and when retrieving join information (using the GXGetStyleJoin or GXGetShapeJoin functions).
The join structure is defined by the gxJoinRecord data type:
struct gxJoinRecord {
   gxJoinAttributeattributes;
   gxShape        join;
   Fixed          miter;
};
Field Description

attributes
Allows you to specify a level join, or to specify one of two standard types of joins: sharp joins and curve joins. The next section, "Join Attributes," describes the gxJoinAttribute flags in detail.
join
Specifies what the join should look like. You must use shapes in their primitive form for the join shape. (Primitive shapes are described in detail in Chapter 4, "Geometric Operations," in this book.) You may not use framed shapes, shapes with an inverse shape fill, full shapes, text shapes, glyph shapes, layout shapes, bitmap shapes, or picture shapes as the join shape.

QuickDraw GX considers only the geometric properties (the shape type, the shape fill, and the shape geometry) of the shape specified by the join field. QuickDraw GX ignores the owner count, shape tags, and shape attributes properties and the style, ink, and transform objects of the join shape.

You set this field to nil when you want to specify a standard join: a sharp join or curve join.
miter
Used to truncate sharp joins. See the next section, "Join Attributes," for more information about sharp joins.
See "Joins" beginning on page 3-25, "Adding Joins to a Shape" beginning on page 3-61, and "Adding Standard Joins to a Shape" beginning on page 3-64 for examples of joins.