Scrollbar bugs in Windows port

Scrollbar bugs in Windows port

[Ralf Angeli]

This is basically a follow-up to the "Scrollbars ?" thread on
emacs-pretest-bug trying to provide test cases for three of the
scrollbar-related bugs in the Windows port of Emacs mentioned in that
thread.

The following was tested with a version checked out and built
2006-05-14.  The font in effect was
-outline-Courier New-normal-r-normal-normal-16-96-120-120-c-*-iso8859-1.

The problems occur under Windows only.  A version built on GNU/Linux
with GTK scrollbars for example is unaffected.

1) If you start Emacs with `emacs -Q', open a file which is longer
   than the window, say etc/DEBUG, move point to the end of the buffer
   and click with mouse-1 on the scrollbar thumb, the buffer will be
   scrolled down by one line upon the mouse-down event.

2) If you start Emacs with `emacs -Q', open etc/DEBUG, click with
   mouse-1 on the scrollbar thumb, drag it down about two thirds of
   the scrollbar and then drag it slowly further down, the buffer will
   shift fastly and eratically up and down during dragging.

3) If you start Emacs with `emacs -Q', open etc/GNU, click with
   mouse-1 on the scrollbar thumb, drag it down to the end of the
   scrollbar and release mouse-1, the last line of the file will not
   be visible.

-- 
Ralf

Re: Scrollbar bugs in Windows port

[Eli Zaretskii]

> From: Ralf Angeli <angeli@caeruleus.net>
> Date: Sun, 04 Jun 2006 23:10:14 +0200
> 
> 1) If you start Emacs with `emacs -Q', open a file which is longer
>    than the window, say etc/DEBUG, move point to the end of the buffer
>    and click with mouse-1 on the scrollbar thumb, the buffer will be
>    scrolled down by one line upon the mouse-down event.
> 
> 2) If you start Emacs with `emacs -Q', open etc/DEBUG, click with
>    mouse-1 on the scrollbar thumb, drag it down about two thirds of
>    the scrollbar and then drag it slowly further down, the buffer will
>    shift fastly and eratically up and down during dragging.
> 
> 3) If you start Emacs with `emacs -Q', open etc/GNU, click with
>    mouse-1 on the scrollbar thumb, drag it down to the end of the
>    scrollbar and release mouse-1, the last line of the file will not
>    be visible.

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.

Thanks.

Re: Scrollbar bugs in Windows port

[Ralf Angeli]

* Eli Zaretskii (2006-06-05) writes:

>> From: Ralf Angeli <angeli@caeruleus.net>
>> Date: Sun, 04 Jun 2006 23:10:14 +0200
>> 
>> 3) If you start Emacs with `emacs -Q', open etc/GNU, click with
>>    mouse-1 on the scrollbar thumb, drag it down to the end of the
>>    scrollbar and release mouse-1, the last line of the file will not
>>    be visible.
>
> I cannot reproduce the last one on my system; maybe it depends on the
> details of the screen resolution.

I tried a few files in etc until I found one where it happens.  Did
you use the same font size as the one I mentioned?

-- 
Ralf

Re: Scrollbar bugs in Windows port

[Eli Zaretskii]

> From: Ralf Angeli <angeli@caeruleus.net>
> Cc: emacs-devel@gnu.org
> Date: Mon, 05 Jun 2006 09:58:27 +0200
> 
> >> 3) If you start Emacs with `emacs -Q', open etc/GNU, click with
> >>    mouse-1 on the scrollbar thumb, drag it down to the end of the
> >>    scrollbar and release mouse-1, the last line of the file will not
> >>    be visible.
> >
> > I cannot reproduce the last one on my system; maybe it depends on the
> > details of the screen resolution.
> 
> I tried a few files in etc until I found one where it happens.  Did
> you use the same font size as the one I mentioned?

I used "emacs -Q".  If one should use other non-default options,
please tell what they are.

Re: Scrollbar bugs in Windows port

[Ralf Angeli]

* Eli Zaretskii (2006-06-05) writes:

>> From: Ralf Angeli <angeli@caeruleus.net>
>> 
>> I tried a few files in etc until I found one where it happens.  Did
>> you use the same font size as the one I mentioned?
>
> I used "emacs -Q".  If one should use other non-default options,
> please tell what they are.

No other default options.  I explicitely removed the Emacs.Font key
from the registry in order for Emacs to use the default font.  But
maybe the default font Emacs picks on your system differs from the one
it picks on mine.  That said, I don't even know if the outcome of the
test case is influenced by the font.

-- 
Ralf

Re: Scrollbar bugs in Windows port

[Jason Rumney]

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.

Re: Scrollbar bugs in Windows port

[Stephan Hennig]

Jason Rumney schrieb:

> 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.

All three bugs are still present in the latest precompiled Windows
binary available on the AUCTeX site.

Regards,
Stephan Hennig

If emacs crashed, and you have the emacs process in the gdb debugger,
please include the output from the following gdb commands:
    `bt full' and `xbacktrace'.
If you would like to further debug the crash, please read the file
d:/Zweitsystem/Programme/Emacs/etc/DEBUG for instructions.


In GNU Emacs 22.0.50.1 (i386-mingw-nt5.1.2600)
 of 2006-06-24 on NEUTRINO
X server distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4) --cflags
-Ic:/Programme/GnuWin32/include'

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: DEU
  locale-coding-system: cp1252
  default-enable-multibyte-characters: t

Major mode: Lisp Interaction

Minor modes in effect:
  encoded-kbd-mode: t
  tooltip-mode: t
  tool-bar-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  unify-8859-on-encoding-mode: t
  utf-translate-cjk-mode: t
  auto-compression-mode: t
  line-number-mode: t

Recent input:
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <menu-bar> <help-menu>
<report-emacs-bug>

Recent messages:
(D:\Zweitsystem\Programme\Emacs\bin\emacs.exe -Q)
Loading encoded-kb...done
For information about the GNU Project and its goals, type C-h C-p.
Loading emacsbug...
Loading regexp-opt...done
Loading emacsbug...done

Re: Scrollbar bugs in Windows port

[Eli Zaretskii]

> From: Stephan Hennig <mailing_list@arcor.de>
> Date: Wed, 28 Jun 2006 21:31:14 +0200
> 
> Jason Rumney schrieb:
> 
> > 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.
> 
> All three bugs are still present in the latest precompiled Windows
> binary available on the AUCTeX site.

That's because no one identified and fixed them yet.  Jason just
simplified the existing code so that whoever will try to fix those
problems won't have hard time figuring out what the code does.

When I have time, I will try to fix this.  I don't know when this will
happen; volunteers are welcome to beat me to it.

Re: Scrollbar bugs in Windows port

[Stephan Hennig]

Eli Zaretskii schrieb:
>> From: Stephan Hennig <mailing_list@arcor.de>
>> 
>> All three bugs are still present in the latest precompiled Windows
>> binary available on the AUCTeX site.
> 
> That's because no one identified and fixed them yet.  Jason just
> simplified the existing code so that whoever will try to fix those
> problems won't have hard time figuring out what the code does.

Since I didn't exactly understand from Jason's reply in what status this
issue was left I just wanted to give some feedback.


> When I have time, I will try to fix this.  I don't know when this will
> happen; volunteers are welcome to beat me to it.

Thanks! Is there a bug database other than the several mailing list
where one can look-up the status of bugs?

Regards,
Stephan Hennig

Re: Scrollbar bugs in Windows port

[Eli Zaretskii]

> From: Stephan Hennig <mailing_list@arcor.de>
> Date: Thu, 29 Jun 2006 11:40:39 +0200
> 
> Is there a bug database other than the several mailing list where
> one can look-up the status of bugs?

Not that I know of.