> So I think that we should remember for each window on the involved frame
> its start and point positions and restore them unless the window is the
> one where the drop happened.  I attached a patch for this which also
> restores the cursor type of every window.  The patch includes all your
> latest changes (so it should apply against the repository version) and
> is largely untested but should give you the idea what to do.

Thank you.  I think that by your revision, the problem was solved.  I
also revised code not to let user drop the text to minibuffer.  This
time, I attach a patch as a separated file.

> Please consider also the following four bindings in `mouse-drag-track':
> 
>          (echo-keystrokes 0)
> 
>          (make-cursor-line-fully-visible nil)
> 
>          ;; Suppress automatic hscrolling, because that is a nuisance
>          ;; when setting point near the right fringe (but see below).
>          (auto-hscroll-mode-saved auto-hscroll-mode)
> 
>          (old-track-mouse track-mouse)
> 
> Maybe they are useful for you as well (a lot of experience went into the
> coding of that function).

I wonder if this is beyond my skill.  Could you revise this part?

> Also please consider to restrict the size of the tooltip shown (think of
> someone who wants to drag the entire text of a buffer).  I think
> `mouse-drag-and-drop-region-show-tooltip' should optionally allow to
> specify a number giving the maximum length of the string which I would
> divide into one half for the beginning of the text, one half for the end
> and ellipses in between.

It is a good idea.  Now tooltip shows only substring.  I think
mouse-drag-and-drop-region-show-tooltip should be something like 256
by default.

> Finally, please think of how to embed your function into other packages:
> For example, how would a user drag file names from one dired buffer to
> another in order to copy or move the associated files from one directory
> to another?  Can we accomodate an exit function to do the pasting job?

It is a good idea.  I suppose you mean dragging `file' when
event-start is with 'dired-filename.