bug#29053: 26.0.90: scroller cannot be dragged to bottom of window

[Alan Third]

On Wed, Nov 01, 2017 at 09:43:46PM +0100, Charles A. Roelli wrote:
> > Date: Wed, 1 Nov 2017 16:52:34 +0000
> > From: Alan Third <alan@idiocy.org>
> > 
> > On Tue, Oct 31, 2017 at 10:12:47PM +0100, Charles A. Roelli wrote:
> > >   (mouseDragged): Handle horizontal case. Call sendScrollEventAtLoc with
> > >   absolute pixel size instead of ratio.
> > 
> > The problem is most likely in here.
<snip>
> > 
> > Does 10.6 have buttons to click at the top and/or bottom of the
> > scrollbar? If so they might affect the offset.
> 
> It has two buttons (up and down), at the bottom of the scrollbar.
> When I drag the scroller as far down as possible, the distance between
> the bottom of the scroller and the pointer (which should be zero)
> looks about the same as the total height of the two buttons, so I
> think you're right.

It was this. Emacs expects the scroller slot to be the same number of
pixels as the whole scroller takes up. When there are buttons within
the scroller area then the slot is smaller.

On modern macOS versions because there are no buttons the use of a
ratio looked silly, but when there are buttons (like on GNUstep too)
then the ratio makes more sense. I shouldn’t have changed it.

I’ve pushed a fix. It works on GNUstep, so I expect it will work for
you too.
-- 
Alan Third