Support drag and drop of region by mouse (Bug#26725)

* doc/emacs/frames.texi (Drag and Drop): Document support of drag
and drop region by mouse.
* lisp/mouse.el (mouse-drag-region): Call mouse-drag-and-drop-region
when start-event is on region.
(mouse-drag-and-drop-region): New function, moves the region by
(mouse-drag-and-drop-region): New defcustom.
* etc/NEWS: Mention mouse-drag-and-drop-region.

1 files changed, 12 insertions, 0 deletions

diff --git a/doc/emacs/frames.texi b/doc/emacs/frames.texi
index 68c12d272f8..8984555066b 100644
--- a/doc/emacs/frames.texi
+++ b/doc/emacs/frames.texi
@@ -1074,6 +1074,18 @@ file on a Dired buffer moves or copies the file (according to the
 conventions of the application it came from) into the directory
 displayed in that buffer.
 
+@vindex mouse-drag-and-drop-region
+  Emacs can also optionally drag the region of text by mouse into
+another portion of this or another buffer.  To enable that, customize
+the variable @code{mouse-drag-and-drop-region} to a non-nil value.
+Normally, the text is moved, i.e. cut and pasted, when the destination
+is the same buffer as the origin; dropping the region on another
+buffer copies the text instead.  If the value of this variable names a
+modifier key, such as @samp{shift} or @samp{control} or @samp{alt},
+then pressing that modifier key when dropping the text will copy it
+instead of cutting it, even if you drop on the same buffer as the one
+from which the text came.
+
 @vindex dnd-open-file-other-window
   Dropping a file normally visits it in the window you drop it on.  If
 you prefer to visit the file in a new window in such cases, customize