bug#45038: 27.1; blank display

bug#45038: 27.1; blank display

[Devon Sean McCullough]

Please see screen shots at http://jovi.net/Emacs-Bug
of a Heisenbug I never saw until maybe a year ago.
Now I see it every day or so.  Hope this helps.

		Peace
			--Devon

In GNU Emacs 27.1 (build 1, x86_64-apple-darwin18.7.0, NS appkit-1671.60 
Version 10.14.6 (Build 18G95))
  of 2020-08-12 built on builder10-14.porkrind.org
Windowing system distributor 'Apple', version 10.3.1671
System Description:  Mac OS X 10.14.6

Configured using:
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Configured features:
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THREADS JSON PDUMPER

Important settings:
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Major mode: Fundamental

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bug#45038: 27.1; blank display

[Stefan Kangas]

Devon Sean McCullough <Emacs-hacker2018@jovi.net> writes:

> Please see screen shots at http://jovi.net/Emacs-Bug
> of a Heisenbug I never saw until maybe a year ago.
> Now I see it every day or so.  Hope this helps.

I see this occasionally as well on master. I have unfortunately not
been able to find a way to reproduce it.

In GNU Emacs 28.0.50 (build 10, x86_64-apple-darwin17.7.0, NS
appkit-1561.61 Version 10.13.6 (Build 17G14042))
 of 2020-12-03 built on SK-MacBook-Pro
Repository revision: a3b596d02ec802f6215af8f552b29cceea6f7eeb
Repository branch: master
Windowing system distributor 'Apple', version 10.3.1561
System Description:  Mac OS X 10.13.6

bug#45038: 27.1; blank display

[Eli Zaretskii]

> From: Devon Sean McCullough <Emacs-hacker2018@jovi.net>
> Date: Thu, 3 Dec 2020 22:33:32 -0500
> 
> Please see screen shots at http://jovi.net/Emacs-Bug
> of a Heisenbug I never saw until maybe a year ago.
> Now I see it every day or so.  Hope this helps.

I think this is a known problem already solved in the repository.  can
you try building the latest emacs-27 branch?

Thanks.

bug#45038: 27.1; blank display

[Stefan Kangas]

Eli Zaretskii <eliz@gnu.org> writes:

> > Please see screen shots at http://jovi.net/Emacs-Bug
> > of a Heisenbug I never saw until maybe a year ago.
> > Now I see it every day or so.  Hope this helps.
>
> I think this is a known problem already solved in the repository.  can
> you try building the latest emacs-27 branch?

I could have sworn I saw this the other week on master.  If you
believe it is fixed, then perhaps I was using an old version at the
time.  Please ignore me for now, I'll report back if I see it again.

bug#45038: 27.1; blank display

[Alan Third]

On Fri, Dec 04, 2020 at 09:45:02AM +0100, Stefan Kangas wrote:
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > > Please see screen shots at http://jovi.net/Emacs-Bug
> > > of a Heisenbug I never saw until maybe a year ago.
> > > Now I see it every day or so.  Hope this helps.
> >
> > I think this is a known problem already solved in the repository.  can
> > you try building the latest emacs-27 branch?
> 
> I could have sworn I saw this the other week on master.  If you
> believe it is fixed, then perhaps I was using an old version at the
> time.  Please ignore me for now, I'll report back if I see it again.

It should be fixed on master, but not in any version of Emacs 27. It's
a large change so was never back ported.

Stefan, if you're still seeing problems on master then there must be
some other problem that I'm unaware of.
-- 
Alan Third

bug#45038: 27.1; blank display

[Eli Zaretskii]

> Date: Fri, 4 Dec 2020 10:53:22 +0000
> From: Alan Third <alan@idiocy.org>
> Cc: Eli Zaretskii <eliz@gnu.org>, 45038@debbugs.gnu.org,
> 	Devon Sean McCullough <Emacs-hacker2018@jovi.net>
> 
> > > I think this is a known problem already solved in the repository.  can
> > > you try building the latest emacs-27 branch?
> > 
> > I could have sworn I saw this the other week on master.  If you
> > believe it is fixed, then perhaps I was using an old version at the
> > time.  Please ignore me for now, I'll report back if I see it again.
> 
> It should be fixed on master, but not in any version of Emacs 27. It's
> a large change so was never back ported.

If it isn't reasonable to release Emacs 27.2 with this problem, we may
wish backporting the change even though it is large.

How easy is it to bump into this problem, and is there an easy
workaround when you do?

bug#45038: 27.1; blank display

[Alan Third]

On Fri, Dec 04, 2020 at 02:02:03PM +0200, Eli Zaretskii wrote:
> > Date: Fri, 4 Dec 2020 10:53:22 +0000
> > From: Alan Third <alan@idiocy.org>
> > Cc: Eli Zaretskii <eliz@gnu.org>, 45038@debbugs.gnu.org,
> > 	Devon Sean McCullough <Emacs-hacker2018@jovi.net>
> > 
> > > > I think this is a known problem already solved in the repository.  can
> > > > you try building the latest emacs-27 branch?
> > > 
> > > I could have sworn I saw this the other week on master.  If you
> > > believe it is fixed, then perhaps I was using an old version at the
> > > time.  Please ignore me for now, I'll report back if I see it again.
> > 
> > It should be fixed on master, but not in any version of Emacs 27. It's
> > a large change so was never back ported.
> 
> If it isn't reasonable to release Emacs 27.2 with this problem, we may
> wish backporting the change even though it is large.
> 
> How easy is it to bump into this problem, and is there an easy
> workaround when you do?

It's unusual to have the display completely blanking, most people just
see small localised glitches. Usually it can be solved by forcing a
redisplay of some sort, which is what you can see in Devon's example
as he moves the cursor across the lines, which forces redisplay of
those lines.

I would prefer not to back-port to Emacs 27, but if you think it's
necessary I'll give it a go.
-- 
Alan Third

bug#45038: 27.1; blank display

[Eli Zaretskii]

> Date: Fri, 4 Dec 2020 13:11:25 +0000
> From: Alan Third <alan@idiocy.org>
> Cc: stefan@marxist.se, 45038@debbugs.gnu.org, Emacs-hacker2018@jovi.net
> 
> > If it isn't reasonable to release Emacs 27.2 with this problem, we may
> > wish backporting the change even though it is large.
> > 
> > How easy is it to bump into this problem, and is there an easy
> > workaround when you do?
> 
> It's unusual to have the display completely blanking, most people just
> see small localised glitches. Usually it can be solved by forcing a
> redisplay of some sort, which is what you can see in Devon's example
> as he moves the cursor across the lines, which forces redisplay of
> those lines.
> 
> I would prefer not to back-port to Emacs 27, but if you think it's
> necessary I'll give it a go.

Given the rarity of the situation and the easy workaround, I agree
that backporting is not required.

Thanks.

bug#45038: 27.1; blank display

[Stefan Kangas]

Alan Third <alan@idiocy.org> writes:

> On Fri, Dec 04, 2020 at 09:45:02AM +0100, Stefan Kangas wrote:
>> Eli Zaretskii <eliz@gnu.org> writes:
>>
>> > > Please see screen shots at http://jovi.net/Emacs-Bug
>> > > of a Heisenbug I never saw until maybe a year ago.
>> > > Now I see it every day or so.  Hope this helps.
>> >
>> > I think this is a known problem already solved in the repository.  can
>> > you try building the latest emacs-27 branch?
>>
>> I could have sworn I saw this the other week on master.  If you
>> believe it is fixed, then perhaps I was using an old version at the
>> time.  Please ignore me for now, I'll report back if I see it again.
>
> It should be fixed on master, but not in any version of Emacs 27. It's
> a large change so was never back ported.
>
> Stefan, if you're still seeing problems on master then there must be
> some other problem that I'm unaware of.

I haven't seen this in a while, although admittedly I haven't been using
my macOS machine much lately.

In any case, I think the bug can be closed if it is fixed on master.
If I see it again, I will just open a new bug.

bug#45038: 27.1; blank display

[Stefan Kangas]

Stefan Kangas <stefan@marxist.se> writes:

> Alan Third <alan@idiocy.org> writes:
>
>> On Fri, Dec 04, 2020 at 09:45:02AM +0100, Stefan Kangas wrote:
>>> Eli Zaretskii <eliz@gnu.org> writes:
>>>
>>> > > Please see screen shots at http://jovi.net/Emacs-Bug
>>> > > of a Heisenbug I never saw until maybe a year ago.
>>> > > Now I see it every day or so.  Hope this helps.
>>> >
>>> > I think this is a known problem already solved in the repository.  can
>>> > you try building the latest emacs-27 branch?
>>>
>>> I could have sworn I saw this the other week on master.  If you
>>> believe it is fixed, then perhaps I was using an old version at the
>>> time.  Please ignore me for now, I'll report back if I see it again.
>>
>> It should be fixed on master, but not in any version of Emacs 27. It's
>> a large change so was never back ported.
>>
>> Stefan, if you're still seeing problems on master then there must be
>> some other problem that I'm unaware of.
>
> I haven't seen this in a while, although admittedly I haven't been using
> my macOS machine much lately.
>
> In any case, I think the bug can be closed if it is fixed on master.
> If I see it again, I will just open a new bug.

I haven't seen this in a while, so let's assume this is fixed.

I'm therefore closing this bug report.