Using Geometric Shapes (IM: XG)

Inside Macintosh: QuickDraw GX Graphics /: Chapter 2 - Geometric Shapes

Using Geometric Shapes
This section shows you how to create, edit, and draw geometric shapes. In particular, this section shows you how to

create and draw empty and full shapes
create point, line, curve, rectangle, polygon, and path shapes
draw points, lines, curves, rectangles, polygons, and paths
create framed and solid shapes
convert a shape from one shape type to another
replace the geometry of a shape
replace geometric points within a shape's geometry
insert geometric points into and remove geometric points from a shape's geometry

All of the sample functions in this section create geometric shapes with default style, ink, and transform information. All shapes are black; framed shapes have one-pixel-wide contours; and the shapes are not rotated, skewed, and so on. For examples of the many stylistic variations you can apply to geometric shapes, see Chapter 3 of this book, "Geometric Styles." For information about inks and transforms, see Inside Macintosh: QuickDraw GX Objects.
Many of the sample functions in this section create geometric shapes and, to do so, they specify geometric points for the shapes' geometries. Since a geometric point contains two fixed-point values (of type Fixed), the sample functions in this section must convert integer constants to fixed-point constants when specifying a geometric point. QuickDraw GX provides the GXIntToFixed macro, which performs this conversion by shifting the integer value 16 bits to the left:
#define GXIntToFixed(a) ((Fixed)(a) << 16)
QuickDraw GX also provides the ff macro as a convenient alias:
#define ff(a) GXIntToFixed(a)
A few of the sample functions in this section specify fractional values for geometric point coordinates. To convert a floating-point value (of type float) to a fixed-point value (type Fixed), QuickDraw GX provides the GXFloatToFixed macro:
#define GXFloatToFixed(a) ((Fixed)((float)(a) * fixed1))
and the synonymous fl macro:
#define fl(a) GXFloatToFixed(a)
IMPORTANT
The GXIntToFixed macro has substantially faster performance than the GXFloatToFixed macro. Whenever possible, you should choose the GXIntToFixed macro over the GXFloatToFixed macro.

Subtopics

Creating and Drawing Empty Shapes and Full Shapes

Creating and Drawing Points

Creating and Drawing Lines

Creating and Drawing Curves

Creating and Drawing Rectangles

Creating and Drawing Polygons

Creating and Drawing Paths

Converting Between Geometric Shape Types

Replacing Geometric Points

Editing Polygon Parts

Editing Paths Parts

Editing Shape Parts