drag events should be defined as a movement to a different buffer position (Bug 9186)

[Andrew Schein]

https://lists.gnu.org/archive/html/bug-gnu-emacs/2011-08/msg00405.html

Back in 2001, the following revision defined the behavior of mouse
movements to cause a drag-copy to occur even when the position within
a buffer does not change:

revno: 40721
committer: Richard M. Stallman <address@hidden>
timestamp: Mon 2001-11-05 04:19:56 +0000
message:
  (read_char): Use Fcar and Fcdr, not Fnth.
  (record_char): Likewise.

  (make_lispy_event): Don't insist a drag event must move to a different
  buffer position.  Instead, check for moving at least double_click_fuzz.

As a result, even clicking on the emacs window is enough to blow away
a pre-existing drag copy buffer if your hand moves even slightly...
making the pasting a drag-copy from a separate window a gamble.   This
is the case if you use your mouse to activate the emacs window instead
of alt-tab or some other mechanism.  Also, the current emacs behavior
is contrary to the user experience of other x-based applications such
as firefox.

Options for fixing this include reverting to a position-based rule or
else creating an emacs lisp variable that controls this behavior (as
exists for turning on/off drag copy altogether).  My patch takes the
former approach.

Cheers,

Andrew

-- 
Andrew I. Schein
www.andrewschein.com