In most graphical desktop environments, Emacs has basic support for drag and drop operations. For instance, dropping text onto an Emacs frame inserts the text where it is dropped. Dropping a file onto an Emacs frame visits that file. As a special case, dropping the 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.
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
the variable dnd-open-file-other-window.
The XDND and Motif drag and drop protocols, and the old KDE 1.x protocol, are currently supported.
It can be difficult to scroll a window or determine where dropped
text will be inserted while dragging text onto an Emacs window.
Setting the option dnd-indicate-insertion-point to a
non-nil value makes point move to the location any dropped text
will be inserted when the mouse moves in a window during drag, and
setting dnd-scroll-margin to an integer value causes a window
to be scrolled if the mouse moves within that many lines of the top
or bottom of the window during drag.
Emacs can also optionally drag the region with the mouse into
another portion of this or another buffer. To enable that, customize
the variable 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 ‘shift’, ‘control’ or
‘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.
In order to cut text even when source and destination buffers differ,
set the option
mouse-drag-and-drop-region-cut-when-buffers-differ to a
non-nil value. By default, on a graphic display the selected
text is shown in a tooltip and point moves together with the mouse
cursor during dragging. To suppress such behavior, set the options
mouse-drag-and-drop-region-show-tooltip and/or
mouse-drag-and-drop-region-show-cursor to nil.
To drag text from Emacs to other programs, set the option
mouse-drag-and-drop-region-cross-program to a non-nil
value.
On the X window system, some programs can drop files on Emacs,
expecting Emacs to save them. Normally, Emacs will prompt for a file
name under which the file will be saved, and then open the file, but
that behavior can be changed by changing the variable
x-dnd-direct-save-function. See Drag and Drop in The
Emacs Lisp Reference Manual.