"wincmd J" on window already at the bottom changes height of other windows

[blueyed]

Using wincmd J on a window that is at the bottom already will resize the windows above.

The following script shows this for a quickfix window, but it happens with a normal window, too.

The help says that it behaves like closing the window, and using :botright split with the old windows' buffer. But using :q | botright split does not resize the windows above.

set noequalalways
fun Heights()
  echom string(map(range(1, winnr('$')), 'winheight(v:val)'))
endfun

e 1
sp 2
copen

call Heights()
wincmd J
call Heights()

[25, 13, 10]
[18, 20, 10]

Using equalalways the behavior is similar, but different still (somehow more expected in this case - apart from that the resizing should have happened with :copen already?!):

[25, 13, 10]
[19, 19, 10]

[chrisbra]

This is explained in the help. Since this is closing and reopening a new window, chaning the dimensions is to be expected.

CTRL-W J        Move the current window to be at the very bottom, using the
                full width of the screen.  This works like closing the current
                window and then creating another one with ":botright split",
                except that the current window contents is used for the new
                window.

[blueyed]

@chrisbra
I've referred to that:

But using :q | botright split does not resize the windows above.

[chrisbra]

okay, reopening then