Filter() is a hook function that's invoked whenever the file panel to which it's been assigned reads the entries in its "panel directory." The function is invoked once for each entry in the directory. All the arguments to the function refer to the entry currently under consideration. (Note that the function is never sent an abstract entry, so the node, st, and filetype arguments will always be valid.)

Your implementation of Filter() can use any or all of the arguments to figure out if the entry is a valid candidate for display in the file panel's file list. Simply return true or false to indicate if the entry is a winner or a loser.

Technically, Filter() is invoked when…

• …the file panel's panel directory is set, either through the BFilePanel constructor or the SetPanelDirectory(), and when…

• …the file panel's Refresh() function is called.

A BRefFilter can be assigned to more than one BFilePanel object (assignation is performed through BFilePanel's constructor or SetRefFilter() function). But it's not probably not a great idea to do so: At any particular invocation of Filter(), the BRefFilter doesn't which BFilePanel object it's working for.

You maintain ownership of the BRefFilter objects that you create. Assigning a ref filter to a file panel does not hand ownership of the BRefFilter to the BFilePanel. You shouldn't delete a BRefFilter while a BFilePanel is still using it; but it's your responsibility to delete it when it's done.