Adding new flags?

[Igor Tarasov]

Hi there!

I try to implement as precise as possible one undocumented feature in
comctl32, this all deals with one structure field. After lots of
testing I know the following:

1. Default value for that field returned by getter is 0.
2. By default it is ignored in behavior.
3. If you change value by the setter, even to 0, behavior changes.
4. Negative values, such as (-1) also produce different behavior and
cannot be used as "field not changed" flag.

So, does that mean that I have to add new flag to the structure that
would be set only if that field is changed, or there is another way to
do that?