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

[Robert Pluim]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Mike Kupfer <mkupfer@alum.berkeley.edu>
>> cc: npostavs@gmail.com, 32002@debbugs.gnu.org, kurn@sfu.ca
>> Date: Thu, 05 Jul 2018 20:58:38 -0700
>> 
>> 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.

Robert