EmptyRect
Rect *theRect ; rectangle to test returns Is theRect empty?
EmptyRect tests to see if a rectangle is empty; i.e., if the bottom border is less than or equal to the top, or the right border is less than or equal to the
left.
theRect is the address of an 8-byte Rect structure. Returns: a Boolean indicating whether the rectangle is empty. It is one of: FALSE Not empty; encloses at least one pixel
Notes: This is functionally equivalent to the following equality test:
( ( theRect.bottom <= theRect.top) || ( theRect.right <= theRect.left) )
When a Toolbox function returns "the empty rectangle", it returns a
rectangle with borders (0,0)(0,0). However, in this function, the
meaning is broader, including all rectangles not enclosing any pixels.