bug#55779: Acknowledgement (29.0.50; child frame)

[drshapeless via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

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Po Lu <luangruo@yahoo.com> (Today 18:27) (replied)
Subject: Re: bug#55779: 29.0.50; child frame
To: drshapeless <drsl@drshapeless.com>
Cc: 55779@debbugs.gnu.org
Date: Fri, 03 Jun 2022 18:27:18 +0800

drshapeless <drsl@drshapeless.com> writes:

> When I build emacs --with-x-toolkit=gtk3, the child frame generated by
> corfu completion candidates are blocked by a blank overlay. I can
[ 7 more citation lines. Click/Enter to show. ]
> confirm this is only a gtk3 related issue, because I have built emacs
> --with-x-toolkit=athena or --with-x-toolkit=no without facing the same
> issue. Also, this issue does not occur on older stable branch,
> e.g. 28.1, I can still use gtk3 as the toolkit on older build without
> any issues.
>
> I have reached out to the author of corfu mode. The author says he
> cannot do anything because it is an issue related to emacs child frame
> mechanism. And my experiments on different build configurations showed
> the same conclusion.

What does "are blocked by a blank overlay" mean?  It is technically
impossible for anything (such as an overlay) in the parent frame to
obscure the contents of the child frame, so I'm afraid I don't
understand what you mean by "blocked"?

Secondly, what happens if you start Emacs with
"GDK_CORE_DEVICE_EVENTS=1" in the environment?

Thanks.
 drshapeless <drsl@drshapeless.com> (0 mins. ago) (sent)
 Subject: Re: bug#55779: 29.0.50; child frame
 To: Po Lu <luangruo@yahoo.com>
 Date: Fri, 03 Jun 2022 20:11:43 +0800

 Po Lu <luangruo@yahoo.com> writes:

 > drshapeless <drsl@drshapeless.com> writes:
 >> When I build emacs --with-x-toolkit=gtk3, the child frame generated by
 [ 18 more citation lines. Click/Enter to show. ]
 >> corfu completion candidates are blocked by a blank overlay. I can
 >> confirm this is only a gtk3 related issue, because I have built emacs
 >> --with-x-toolkit=athena or --with-x-toolkit=no without facing the same
 >> issue. Also, this issue does not occur on older stable branch,
 >> e.g. 28.1, I can still use gtk3 as the toolkit on older build without
 >> any issues.
 >>
 >> I have reached out to the author of corfu mode. The author says he
 >> cannot do anything because it is an issue related to emacs child frame
 >> mechanism. And my experiments on different build configurations showed
 >> the same conclusion.
 >
 > What does "are blocked by a blank overlay" mean?  It is technically
 > impossible for anything (such as an overlay) in the parent frame to
 > obscure the contents of the child frame, so I'm afraid I don't
 > understand what you mean by "blocked"?
 >
 > Secondly, what happens if you start Emacs with
 > "GDK_CORE_DEVICE_EVENTS=1" in the environment?
 >
 > Thanks.

 I just tried starting Emacs with "GDK_CORE_DEVICE_EVENTS=1", the only
 difference is the smooth scrolling is gone. The child frame issue still
 persists.

 To be clear, it was said to be a child frame redisplay bug, (by
 minad). It was not the parent frame blocking the child frame, instead it
 seems to be another child frame blocking the child frame.

 You may check out the github issue below, where I posted a couple photos
 showing the bug.

 https://github.com/minad/corfu/issues/161