Volume 7A: XView Programming Manual

Example 10-3. Scrollbar compute scroll procedure example (continued)

xv_set(sb, SCROLLBAR_VIEW_LENGTH, last_plus_one - first,

0);

*offset = first;

return (XV_OK);

}

In this example, the textsw package keeps track of the object size based on the number of

characters in the view. When the user scrolls, the object length will most probably change, so

the textsw package uses its own compute scroll procecure to calculate a new object length

and offset each time there is a scroll request. This is needed for cases when the user scrolls

backwards and data is still coming into the textsw, so the object length grows (the propor-

tional indicator shrinks).

10.4.2.1 Indicating scrollbar motion

The attribute

SCROLLBAR_MOTION provides the scrolling motion that resulted during a

scrollbar_request event. This attribute is get only. Possible valid motions returned are:

ABSOLUTE

POINT_TO_MIN (from here_to_top on menu)

PAGE_FORWARD

LINE_FORWARD

MIN_TO_POINT (from top_to_here on menu)

PAGE_BACKWARD

LINE_BACKWARD

TO_END

TO_START

PAGE_ALIGNED

10.4.3 Providing a Scrollbar Normalize Procedure

The scrollbar package provides for a special offset routine that may be used to adjust the new

scroll position before the scrollbar package scrolls to the starting location computed by the

scrollbar compute procedure. This special offset routine, called the normalize procedure,

allows you to perform a scroll adjustment when, for example, the ...