bug#31240: 26.1; mouse-save-then-kill does not kill rectangles

[martin rudalics]

> The example Homeros tried to run won't work, because the newly intersected
> rectangle would intersect the original rectangle. This behaviour is
> intentional, as it
> is similar to mouse-drag-and-drop-region's behaviour with non-rectangle 
regions.
>
> However, I think an exception could be made for rectangle operations move the
> rectangle horizontally to the left, as Tak said. When the rectangle is
> dragged to the left,
> there's no way its content could be accidentally added to the overlays
> tracking the original
> rectangle, so it'll always work correctly (even if
> rectangle-intersect-p returns t).

FWIW I see no problems with the following naive amendment

                           (let ((size (cons region-width region-height)))
                             (and (rectangle-intersect-p
                                   (rectangle-position-as-coordinates start) 
size
                                   (rectangle-position-as-coordinates 
point-to-paste) size)
                                  (not (= (line-number-at-pos start)
                                          (line-number-at-pos 
point-to-paste)))))

which also allows shifting the rectangle strictly to the left or
right.  IIUC it's the deletion of the original rectangle after the
copy was inserted on a different line that's causing havoc with
intersections.  But I have not tested all possible variants so please
correct me if I'm wrong.

martin