Re: master a1a435b3f6: Respect test function when performing local drag-and-drop

[Eli Zaretskii <eliz@gnu.org>]

> From: Po Lu <luangruo@yahoo.com>
> Cc: emacs-devel@gnu.org
> Date: Tue, 14 Jun 2022 10:51:06 +0800
> 
> How about this?
> 
> Function called for the return value of `x-begin-drag' when dropping on a frame.
> 
> It should accept two arguments POS and ACTION, and return a symbol
> describing what to return from `x-begin-drag' if the drop happens on a
> frame.  POS is a mouse position list detailing the location of the drop,
> and ACTION is the action specified by the caller of `x-begin-drag'.
> 
> If nil or a non-symbol value is returned, the drop will be cancelled.

Suggest a slight rewording:

  Function that determines return value of drag-and-drop on Emacs frames.

  If the value is a function, `x-begin-drag' will call it with two
  arguments, POS and ACTION, where POS is a mouse position list
  that specifies the location of the drop, and ACTION is the action
  specified by the caller of `x-begin-drag'.  The function should
  return a symbol describing what to return from `x-begin-drag' if the
  drop happens on an Emacs frame.

  If the value is nil, or the function returns a value that is not a
  symbol, a drop on an Emacs frame will be canceled.