The BRefFilter class lets you filter the items that a file panel is about to display. This filtering is performed by the class' only function, Filter(). Filter() is a hook function; to use a BRefFilter, you have to create a derived class and implement the Filter() function.

To assign your BRefFilter object to a file panel, you invoke BFilePanel's SetRefFilter() function. (The BFilePanel constructor also lets you set the filter.) If you don't specifically assign a filter, the file panel will not have one—there is no "default" ref filter object. You maintain ownership of the BRefFilter that you assign to a file panel; the file panel doesn't delete or otherwise change your object.

You can assign the same filter to more than file panel. However, the Filter() function isn't told which panel it's being invoked for.