> Ahem, not so sure what you'd want here.  But playing with your
 >
 >  >   emacs -Q
 >  >   (message (make-string 1000 ?a))
 >  >   C-x C-e
 >
 > example, which btw. give me only 8 lines, whit the initial quote out of
 > sight, you can easily reproduce this:
 >
 > Split *scratch* horizontally

... vertically (the new window is below the old one) ...

 > and then click on the 1 of 1000.

... in the new, lower window.

 > The
 > minibuffer shrinks, the 1 is blinking, but the mouse is no over the n of
 > notes, which slid down.  When letting go, the n blinks and all up to
 > before 1000 is marked.

I can see that.

 > Independently of resizing, something similar happens for sideways
 > scrolling:  Split *scratch* vertically, click on the v of visit,

What is the "v of visit"?

 > nothing
 > happens (that's where it dffers).  But then move the mouse 1 char right,
 > this triggers a sideways scroll.  The mouse is now over the e of file.
 > When letting go, it marks "visit that fil" but worse, it scrolls yet
 > again by the same amount, so that the mouse is now at the end of the
 > line, far from the text it marked.
 >
 > I'd expect both cases to consistently do something only when I release
 > the mouse, or when I drag to outside the window to force scrolling.

Can you try the attached patch?

Thanks, martin