Implement threading for the search button and implement a 'Stop' button to interrupt the process.
The result list is now cleared everytime you search again when the result list was not empty.
The result box is now updated while watching, rather than having a huge delay and suddenly a full result list.
The filename search field now returns an error when a directory is given.
Code optimization: no need to iterate over files twice everytime.
The full path is now shown (if the checkbox to show dir is checked) and checking or unchecking will update current results from now on.
Increase size of the application significantly so the chances of seeing the full path of a file are increased.