Re: Scrollbar bugs in Windows port

[Jason Rumney <jasonr@gnu.org>]

Eli Zaretskii <eliz@gnu.org> writes:

> I cannot reproduce the last one on my system; maybe it depends on the
> details of the screen resolution.  I will try to look into the other
> two when I have time.

I can reproduce all three, I think they are related - perhaps an
off-by-one or rounding bug somewhere in the calculations that relate
scrollbar position to buffer position and vice-versa. I have looked at
this code several times in the past, but whenever I've made changes to
fix one test case, something else has broken. I had another look now,
and noticed that part of the confusion is caused by workarounds for
obsolete versions of Windows NT that we haven't supported since at
least Emacs 19.34. So I simplified the code for anyone who wants to
look at it (in w32term.c, search for SCROLLINFO). I also noticed that
there are a lot of places in the code that deal with scrolling, so
perhaps the problem in the past is that only some of those got
updated.