bug#32002: 24.4; Scroll bar start, end not correct

[Eli Zaretskii]

> Date: Fri, 06 Jul 2018 14:56:10 +0200
> From: martin rudalics <rudalics@gmx.at>
> CC: Mike Kupfer <mkupfer@alum.berkeley.edu>, 32002@debbugs.gnu.org, 
>  kurn@sfu.ca, npostavs@gmail.com
> 
>  >>> gdb says that Emacs is getting jump events, not step events.
>  >>>
>  >>>    Thread 1 "emacs" hit Breakpoint 1, xg_scroll_callback 
> (range=0x2f58740,
>  >>>        scroll=GTK_SCROLL_JUMP, value=5637316.2000000002,
>  >>>        user_data=0x1493c30 <bss_sbrk_buffer+8990864>) at xterm.c:5644
>  >>
>  >> Thanks.  I guess the issue now moves to GTK-land: why do we get jump
>  >> events when you click on the steppers?  Maybe someone who knows GTK
>  >> can answer that.
>  >
>  > It looks like GTK sends GTK_SCROLL_JUMP everytime the position of the
>  > scrollbar thumb is changed, regardless of how you change it. I think
>  > it can *also* send events when you click the stepper, but I suspect
>  > you then get two events, with no easy way to distinguish them. Iʼd
>  > test, but my theme doesnʼt have steppers.
> 
> Here I'm called back with exactly one GTK_SCROLL_STEP notification as
> 
> #0  xg_scroll_callback (range=0x183a3b0, scroll=GTK_SCROLL_STEP_FORWARD, 
> value=244073, user_data=0x15410a0) at ../../src/xterm.c:5673

So maybe the GTK version is a factor here?