bug#16647: Imprecisions with window-resizing cursors

[N. Jackson]

At 15:07 -0400 on Saturday 2014-02-22, E. Sabof wrote:

> martin rudalics <rudalics@gmx.at> writes:
>
>> I'm beginning to suspect that something strange is going on somewhere
>> between Emacs and the input device.  Could you try playing a bit with
>> `mouse-autoselect-window'?  More precisely, how soon (in pixels) it
>> selects a window when you move the mouse into it from another one.
>
> Everything works as it should, as far as I can tell. Both horizontally and 
> vertically.
>
> Evgeni

With mouse-autoselect-window set to t, I also see everything working as
I expect it should (with GTK+ Version 3.8.8 as before). (But note the
interesting "however" in the last paragraph.)

    emacs -Q
    M-: (setq mouse-autoselect-window t) RET
    M-: (setq scroll-bar-mode -1) RET
    M-x (split-window-right) RET

Moving the mouse from the right, into the left window, the left window
is selected immediately I cross the vertical line and the mouse cursor
changes to the <=> at the same time.

Moving the mouse from the left, into the right window, the right window
is selected immediately I cross the vertical line. Mostly the mouse cursor
does not change though (as previously reported).

    emacs -Q
    M-: (setq mouse-autoselect-window t) RET
    M-: (set-frame-parameter nil 'right-divider-width 24) RET
    M-x (split-window-right) RET

Moving the mouse from the right, towards the left window, the left
window is selected immediately I cross the right edge of the vertical
line and the mouse cursor changes to the <=> at the same time.

Moving the mouse from the left, towards the right window, the mouse
cursor changes to the <=> immediately I cross the left edge of the
vertical line. The right window is selected immediately the mouse cursor
crosses the right edge of the the vertical line. _However_, the mouse
cursor stays as a <=> for a few pixels more movement to the right, and
it is at this time that, if it is clicked, it doesn't do anything, as
per Evgeni's original bug.

N.