Right now I have backup and swapfile turned off in my vimrc, like this
set nobackup
set noswapfile
and everything works fine. But if I decide to turn backup and swapfile on
set backup
set swapfile
then vim starts acting differently. For example, if I try to use nerdtree (I have F4 mapped to :NERDTreeToggle) I'll hit F4 and the entire screen will go blank, prompting me to hit enter to continue.
But when I have backup and swapfile turned off hitting F4 opens nerdtree like normal. Why does this happen? How do I turn on backup and swapfile without changing the behavior of vim?