x-dnd-test-function

x-dnd-test-function is a variable defined in `x-dnd.el'.
Its value is

x-dnd-default-test-function

• This variable may be risky if used as a file-local variable.

Documentation:
The function drag and drop uses to determine if to accept or reject a drop.
The function takes three arguments, WINDOW, ACTION and TYPES.
WINDOW is where the mouse is when the function is called. WINDOW may be a
frame if the mouse isn't over a real window (i.e. menu bar, tool bar or
scroll bar). ACTION is the suggested action from the drag and drop source,
one of the symbols move, copy, link or ask. TYPES is a list of available
types for the drop.

The function shall return nil to reject the drop or a cons with two values,
the wanted action as car and the wanted type as cdr. The wanted action
can be copy, move, link, ask or private.
The default value for this variable is `x-dnd-default-test-function'.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 22.1 of Emacs.