Hi!

I think you simply haven't mapped the horizontal events to anything.
ns-win.el contains the following:

(global-set-key [vertical-scroll-bar down-mouse-1]
'ns-handle-scroll-bar-event)
(global-unset-key [vertical-scroll-bar mouse-1])
(global-unset-key [vertical-scroll-bar drag-mouse-1])

If I do the same with `horizontal-scroll-bar' I can drag it around, and
Emacs react to it. (Unfortunately, it then scroll the window vertically
rather than horizontally, but that just a technicality :)

Also, if you evaluate (read-key-sequence "Click on something: ") and either
click on the empty space next to the scroll bar or drag it, it will return
events with the type `horizontal-scroll-bar'.

Thanks for starting to work on the NS port!

    -- Anders


On Sun, Apr 24, 2016 at 6:01 PM, Alan Third <alan@idiocy.org> wrote:

> I've been trying to complete the horizontal scroll-bars implementation
> in the NS port and have run into a bit of a problem I can't work out.
>
> They display correctly, and when you click on them they, I think, send
> a correctly formatted emacs_event, but nothing happens. Vertical
> scroll-bars work as expected.
>
> Have I missed somewhere where I need to enable the horizontal
> scroll-bar events or something? Any pointers would be appreciated.
>
> I've attached a patch containing what I've done so far.
> --
> Alan Third
>