bug#51343: 27.2; Xaw3d scrollbar thumb doesn't update while dragged

bug#51343: 27.2; Xaw3d scrollbar thumb doesn't update while dragged

[Po Lu via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Previously, in an Emacs built with Xaw3d scroll bars, the thumb
proportion would update as the scrollbar was dragged.  Now it doesn't
update until the scrollbar is released, and something that makes the
scrollbar position change happens.

Thanks.

In GNU Emacs 27.2 (build 2, i386-unknown-linux-gnu, X toolkit, Xaw3d scroll bars)
of 2021-10-21 built on vendetta
Windowing system distributor 'The X.Org Foundation', version 11.0.12101001

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Configured using:
'configure --prefix=/opt/gsb'

Configured features:
XAW3D XPM JPEG TIFF GIF PNG RSVG SOUND GPM DBUS GCONF GLIB ACL
LIBSELINUX LIBXML2 FREETYPE XFT ZLIB TOOLKIT_SCROLL_BARS LUCID X11 XDBE
XIM MODULES THREADS PDUMPER 

bug#51343: 27.2; Xaw3d scrollbar thumb doesn't update while dragged

[Eli Zaretskii]

> Date: Sat, 23 Oct 2021 15:32:48 +0800
> From:  Po Lu via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> Previously, in an Emacs built with Xaw3d scroll bars, the thumb
> proportion would update as the scrollbar was dragged.  Now it doesn't
> update until the scrollbar is released, and something that makes the
> scrollbar position change happens.

Could you please bisect to find the commit which changed that?

Thanks.

bug#51343: 27.2; Xaw3d scrollbar thumb doesn't update while dragged

[Po Lu via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Eli Zaretskii <eliz@gnu.org> writes:

> Could you please bisect to find the commit which changed that?

Do you mean `git bisect'?  I tried using it for Emacs not long ago, but
after a while odd build errors started cropping up.

Eventually, I got to a point where I had to run `make bootstrap' before
each build, and it started taking too long.

Is there anything in particular that I'm missing and can be used to
speed up the build?  Thanks in advance.

bug#51343: 27.2; Xaw3d scrollbar thumb doesn't update while dragged

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: 51343@debbugs.gnu.org
> Date: Sat, 23 Oct 2021 17:56:52 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Could you please bisect to find the commit which changed that?
> 
> Do you mean `git bisect'?

Yes.

> I tried using it for Emacs not long ago, but after a while odd build
> errors started cropping up.
> 
> Eventually, I got to a point where I had to run `make bootstrap' before
> each build, and it started taking too long.
> 
> Is there anything in particular that I'm missing and can be used to
> speed up the build?  Thanks in advance.

"make -j10 bootstrap", perhaps?

bug#51343: 27.2; Xaw3d scrollbar thumb doesn't update while dragged

[Po Lu via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Eli Zaretskii <eliz@gnu.org> writes:

> "make -j10 bootstrap", perhaps?

Sadly, I don't have the luxury of a processor with 10 execution units,
at least on the machine that exhibited the problem.  Plain -j2 will have
to do.

But I will bisect tomorrow and let you know the results.  Thanks :)

bug#51343: 27.2; Xaw3d scrollbar thumb doesn't update while dragged

[Glenn Morris]

Po Lu wrote:

> Is there anything in particular that I'm missing and can be used to
> speed up the build?

You don't need to compile all the lisp files for this kind of problem.
For bisecting, I use:

make maintainer-clean >& /dev/null
autoreconf -fi -I m4
./configure [...] --cache-file=/tmp/ccache
make -C lib [-j #] all
make -C src [-j #] emacs

bug#51343: 27.2; Xaw3d scrollbar thumb doesn't update while dragged

[Po Lu via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Glenn Morris <rgm@gnu.org> writes:

> You don't need to compile all the lisp files for this kind of problem.
> For bisecting, I use:
>
> make maintainer-clean >& /dev/null
> autoreconf -fi -I m4
> ./configure [...] --cache-file=/tmp/ccache
> make -C lib [-j #] all
> make -C src [-j #] emacs

Thanks, this helped a lot.

This problem exists all the way back to Emacs 25, and probably earlier.
However, at that point, I wasn't able to continue building Emacs on my
system, probably due to some functions for peeking at file streams being
removed from glibc.

bug#51343: 27.2; Xaw3d scrollbar thumb doesn't update while dragged

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: Eli Zaretskii <eliz@gnu.org>,  51343@debbugs.gnu.org
> Date: Sun, 24 Oct 2021 10:15:02 +0800
> 
> This problem exists all the way back to Emacs 25, and probably earlier.

Thanks.  Can you try figuring out in which released Emacs version this
started happening?

bug#51343: 27.2; Xaw3d scrollbar thumb doesn't update while dragged

[Po Lu via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Eli Zaretskii <eliz@gnu.org> writes:

> Thanks.  Can you try figuring out in which released Emacs version this
> started happening?

Sometime between 23.4 and 25.1.  I built 23.4 with the Gentoo patches
(strictly limited to resolving build problems), and it seems to work
fine, but this functionality is broken in 25.1.

Thanks.

bug#51343: 27.2; Xaw3d scrollbar thumb doesn't update while dragged

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: rgm@gnu.org,  51343@debbugs.gnu.org
> Date: Sun, 24 Oct 2021 14:28:35 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Thanks.  Can you try figuring out in which released Emacs version this
> > started happening?
> 
> Sometime between 23.4 and 25.1.  I built 23.4 with the Gentoo patches
> (strictly limited to resolving build problems), and it seems to work
> fine, but this functionality is broken in 25.1.

Thanks, I guess this means you have to step with a debugger into
x_set_toolkit_scroll_bar_thumb and see when it is called and what
values it produces, and perhaps compare between 23.4 and the current
code base.

bug#51343: 27.2; Xaw3d scrollbar thumb doesn't update while dragged

[Po Lu via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Eli Zaretskii <eliz@gnu.org> writes:

> Thanks, I guess this means you have to step with a debugger into
> x_set_toolkit_scroll_bar_thumb and see when it is called and what
> values it produces, and perhaps compare between 23.4 and the current
> code base.

The Athena code in x_set_toolkit_scroll_bar_thumb has stayed the same
over those releases, and they are called under almost the same
circumstances in both releases.  IOW, XawScrollbarSetThumb is called
with the appropriate value in both releases, so that's not the problem
here.

I'm at a loss, and I don't know what else could possibly be affecting
this.  Perhaps someone else knows what the problem might be?

Thanks.

bug#51343: 27.2; Xaw3d scrollbar thumb doesn't update while dragged

[Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Po Lu [2021-10-23 15:32:48] wrote:
> Previously, in an Emacs built with Xaw3d scroll bars, the thumb
> proportion would update as the scrollbar was dragged.  Now it doesn't
> update until the scrollbar is released, and something that makes the
> scrollbar position change happens.

To give you some context:

Many years ago, I spent a fair bit of time trying to get scrollbars
working "right".  It's a major pain in the ass, because most toolkits
don't support our requirements: once the bottom of the thumb hits the
bottom of its course it stops there, but the corresponding top part of
the thumb may correspond to a window-start which leads to a screen where
point-max is not visible (in response to which we'd reduce the size of
the thumb, but that happens too late (either because the toolkit has
already decided not to tell us that the user's mouse was trying to go
further, or because the toolkit doesn't support updating the thumb size
while dragging it).

There was a simple patch to Xaw3d which made it behave more like Xaw (by
making the Xaw3d more like Xaw's) and made the whole thing work
perfectly for us, but it was never accepted upstream because it went
against their philosophy of what "the metaphor should be".


        Stefan

bug#51343: 27.2; Xaw3d scrollbar thumb doesn't update while dragged

[Po Lu via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> Po Lu [2021-10-23 15:32:48] wrote:
>> Previously, in an Emacs built with Xaw3d scroll bars, the thumb
>> proportion would update as the scrollbar was dragged.  Now it doesn't
>> update until the scrollbar is released, and something that makes the
>> scrollbar position change happens.
>
> To give you some context:
>
> Many years ago, I spent a fair bit of time trying to get scrollbars
> working "right".  It's a major pain in the ass, because most toolkits
> don't support our requirements: once the bottom of the thumb hits the
> bottom of its course it stops there, but the corresponding top part of
> the thumb may correspond to a window-start which leads to a screen where
> point-max is not visible (in response to which we'd reduce the size of
> the thumb, but that happens too late (either because the toolkit has
> already decided not to tell us that the user's mouse was trying to go
> further, or because the toolkit doesn't support updating the thumb size
> while dragging it).
>
> There was a simple patch to Xaw3d which made it behave more like Xaw (by
> making the Xaw3d more like Xaw's) and made the whole thing work
> perfectly for us, but it was never accepted upstream because it went
> against their philosophy of what "the metaphor should be".

This particular feature used to work in Emacs 23 though, so that can't
be the entirety of the problem.

bug#51343: 27.2; Xaw3d scrollbar thumb doesn't update while dragged

[Po Lu via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> My crystal ball suggests 6ca5360192fbe50abd5e43ba2ed28aa115af4d65 as the
> cause for this change.

That worked for old versions of Xaw3d, but setting scroll_mode manually
is enough to make recent versions of Xaw3d crash.

Besides, it worked in Emacs 23, which that code wasn't in.
Thanks.

bug#51343: 27.2; Xaw3d scrollbar thumb doesn't update while dragged

[Lars Ingebrigtsen]

Po Lu <luangruo@yahoo.com> writes:

> Previously, in an Emacs built with Xaw3d scroll bars, the thumb
> proportion would update as the scrollbar was dragged.  Now it doesn't
> update until the scrollbar is released, and something that makes the
> scrollbar position change happens.

I can reproduce this in Emacs 29 with

./configure --with-x-toolkit=athena

and a buffer that contains alternating blocks of short/long lines.