NAME
    FilterTagChanges -- Eliminate TagItems which specify no change. (V36)

SYNOPSIS
    FilterTagChanges( changeList, oldValues, apply)
                      A0          A1         D0

    void FilterTagChanges( struct tagitem *changelist,
                           struct tagitem *oldvalues, long apply );

FUNCTION
    Eliminate items from a "change list" that specify values already
    in effect in existing list.  Optionally update the existing list
    if the Boolean 'Apply' is true.

    The elimination is done by changing the ti_Tag field to TAG_IGNORE.
    So, this function may change the input tag list(s).

INPUTS
    changeList      - specification of new tag-value pairs.
    oldValues       - a list of existing tag item pairs.
    apply           - Boolean specification as to whether the values in
                      oldValues are to be updated to the values in
                      changeList.

RESULT
    None.

EXAMPLE
    Assume you have an attribute list for an object (oldValues)
    which looks like this:

            ATTR_Size,  "large",
            ATTR_Color, "orange",
            ATTR_Shape, "square",

    If you receive a new TagList containing some changes (changeList),
    which looks like this:

            ATTR_Size,  "large",
            ATTR_Shape, "triangle"

    If you call FilterTagChanges(), changeList will be modified to
    contain only those attributes which are different from the
    oldValues.  All other tagitems will have their tag-values set to
    TAG_IGNORE.  The resulting changeList will become:

            TAG_IGNORE, "large",
            ATTR_Shape, "triangle"

    If apply was set to TRUE, oldValues would be:

            ATTR_Size,  "large"
            ATTR_Color, "orange"
            ATTR_Shape, "triangle"

BUGS

SEE ALSO