bug#61337: 29.0.60; Setting frame-title-format makes Emacs to steal focus

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

Eli Zaretskii <eliz@gnu.org> writes:

> Which part? the change in xfns.c is fine (it just makes the code
> slower, so perhaps test EQ first and Fstring_equal if EQ doesn't
> return non-zero)

Just the change in xfns.c.  It fixes a bug in the original code (which
was trying to test whether or not both strings were equal, but didn't
handle the case where the strings were equal, but not EQ.)

>, but if someone sets icon-title-format in a way that
> produces a different string from what frame-title-format does, it will
> not work.  And forcing these two formats to produce the same strings
> is definitely NOT okay, not for emacs-29, not ever.

That isn't the change here.

> However, to tell the truth, I don't really understand the phenomenon
> being complained about in this case.  The original report says: "the
> z-order is not altered", whereas the conclusion of the analysis is
> "KWin seems to treat this as Emacs asking to be focused".  Would you
> please describe the problem in easier-to-understand terms and use the
> user-facing behavior instead of technical terms like z-order, so that
> I could at least make up my mind whether this issue is serious, and
> perhaps think about alternative solutions?  E.g., I don't yet
> understand why returning early in x_set_title should help here, and
> how.

The problem is that KWin apparently focuses a window if its title
changes while it is in a different workspace.  That's misbehavior on
KWin's part, and likely a bug.

Since moving to a different desktop is a form of iconification under X,
Emacs switches to displaying the icon title.

The change to xfns.c prevents Emacs from changing the title if the icon
title is identical to the frame title, which should make it possible to
work around the problem by setting icon-title-format to the same text as
frame-title-format; the rest is something that can only be fixed by its
developers.

The problem does not exist in Emacs 28, because icon-title-format did
not work there at all.

Thanks.