Legacy Document

Inside Macintosh: Imaging With QuickDraw /

Chapter 3 - QuickDraw Drawing / QuickDraw Drawing Reference

Routines / Drawing Rectangles

EraseRect

To erase a rectangle, use the EraseRect procedure.

PROCEDURE EraseRect (r:\xDDRect);

r

The rectangle to erase.

DESCRIPTION

Using the patCopy pattern mode, the EraseRect procedure draws the interior of the rectangle that you specify in the r parameter with the background pattern for the current graphics port. This effectively erases the rectangle specified in the r parameter. For example, you can use EraseRect to erase the port rectangle for a window before redrawing into the window.

This procedure leaves the location of the graphics pen unchanged.

SPECIAL CONSIDERATIONS

The EraseRect procedure may move or purge memory blocks in the application heap. Your application should not call this procedure at interrupt time.

SEE ALSO

Listing 6-2 on page 6-10 in the chapter "Offscreen Graphics Worlds" in this book illustrates how to use EraseRect to initialize an offscreen pixel map. The patCopy pattern mode is described in "Boolean Transfer Modes With 1-Bit Pixels" beginning on page 3-7.