Inside Macintosh: QuickDraw GX Objects /

Chapter 6 - Transform Objects / Transform Objects Reference

Functions / Transforming Shapes by Modifying Shape Geometries

GXScaleShape

You can use the GXScaleShape function to scale a shape by specified horizontal and vertical factors about a specified origin.

void GXScaleShape(gxShape target, Fixed hScale, Fixed vScale,
                  Fixed xOffset, Fixed yOffset);

target

A reference to the shape you want to scale.

hScale

The horizontal scaling factor.

vScale

The vertical scaling factor.

xOffset

The horizontal coordinate of the origin to scale the shape about.

yOffset

The vertical coordinate of the origin to scale the shape about.

DESCRIPTION

The GXScaleShape function scales the shape referenced by the target parameter horizontally by the factor specified in the hScale parameter and vertically by the factor specified in the vScale parameter. The scaling is centered about the origin specified in the xOffset and yOffset parameters. (The origin is the point whose coordinates do not change as a result of the scaling operation.)

This function scales the target shape in one of two ways:

• If the target shape's gxMapTransformShape attribute is cleared, the function recalculates the control points of the shape's geometry to effect the scaling.
• If the target shape's gxMapTransformShape attribute is set, this function is identical to the GXScaleTransform function; it recalculates the mapping matrix of the target shape's transform object to effect the scaling. If the target shape shares this transform object with other shapes, QuickDraw GX makes a copy of the transform object, associates the copy with the target shape, and makes changes to the copy.

The target shape can be any shape type. However, if the target shape is an empty shape, a full shape, or a picture shape, this function has no effect unless the shape's gxMapTransformShape attribute is set.

The coordinates of the origin are specified in geometry space.

ERRORS, WARNINGS, AND NOTICES

Errors
out_of_memory
shape_is_nil
shape_access_not_allowed	(debugging version)
Warnings
scale_shape_out_of_range
graphic_type_cannot_be_moved
Notices (debugging version)
mapping_unaffected

SEE ALSO

For examples of the use of this function, see Listing 6-4 on page 6-25 and Listing 6-5 on page 6-27.

To scale a shape by altering the mapping property of its transform object, you can also use the GXScaleTransform function, described on page 6-60.