subclassing MinMaxInfo

[Lord Orwell]

First of all, you should ALWAYS call the default message handler.
2nd of all, how small? Windows won't let you prevent it from resizing smaller than a certain point, due to the fact this would prevent window minimizing, which is really just resizing a window and moving it down. check the dimensions of a window next time you minimize it. I don't see anything wrong with your code (except the case part).

Lord Orwell: There are times when calling the default the message handler are not necessary. For example, if you do this while doing a type of paint operation (like painting a subclassed messagebox) then it will not work.

[Lord Orwell]

really? I was under the impression that if you didn't pass the info on to the message handler always, that it could miss other messages that are sent at the same time.