is a variable defined in `
C source code
Its value is
- This variable may be risky if used as a file-local variable.
Functions run before deleting a frame.
The functions are run with one arg, the frame to be deleted.
Note that functions in this list may be called just before the frame is
actually deleted, or some time later (or even both when an earlier function
in `delete-frame-functions' (indirectly) calls `delete-frame'