bug#23368: 25.0.92; xftfont.c has got a bug

[Eli Zaretskii]

> Date: Mon, 25 Apr 2016 15:02:40 +0900
> From: Masaru Nomiya <nomiya@galaxy.dti.ne.jp>
> 
> Hello,
> 
> With Emacs 25.0.92, Emacs 25.0.93, and Emacs 25.1.50, Emacs start to
> use 100% CPU.
> That is, afetr I start Wanderlust(MUA) on Emacs, and try to open some
> folders in it, Emacs starts to use 100% CPU, and unresposible.
> 
> I investigated the latest Emacs with git bisect.
> As a result, I found that xftfont.c has got a bug as follows.

CC'ing Handa-san.  This seems to be a duplicate of bug#23360.  Can you
tell which font(s) are used by Wanderlust when this happens?

> --------------------------------------------------------------------
> masaru@linux-uw5l:/tmp/tes/emacs> git checkout emacs-25
> Branch emacs-25 set up to track remote branch emacs-25 from origin.
> Switched to a new branch 'emacs-25'
> 
> masaru@linux-uw5l:/tmp/tes/emacs> git bisect start
> 
> masaru@linux-uw5l:/tmp/tes/emacs> git bisect bad
> 
> masaru@linux-uw5l:/tmp/tes/emacs> git bisect good emacs-25.0.91
> Bisecting: 182 revisions left to test after this (roughly 8 steps)
> [04f5525fbb961f6006280be340ca0f03df9e80a7] Make '.' associative, for easier 
> sexp navigation
> 
> masaru@linux-uw5l:/tmp/tes/emacs> ./autogen.sh
> 
> masaru@linux-uw5l:/tmp/tes/emacs> ./configure
> 
> masaru@linux-uw5l:/tmp/tes/emacs> make bootstrap -j10
> 
> test --  NG
> 
> masaru@linux-uw5l:/tmp/tes/emacs> make clean
> 
> masaru@linux-uw5l:/tmp/tes/emacs> git bisect bad
> Bisecting: 90 revisions left to test after this (roughly 7 steps)
> [06a872b71d6580e0699600844bb9526602437990] Fix redisplay on a TTY after 
> 'make-frame'
> [...]
> masaru@linux-uw5l:/tmp/tes/emacs> make bootstrap -j10
> 
> test  --  OK
> 
> masaru@linux-uw5l:/tmp/tes/emacs> make clean
> 
> masaru@linux-uw5l:/tmp/tes/emacs> git bisect good
> Bisecting: 0 revisions left to test after this (roughly 1 step)
> [ec10ef95cf2a5309ec7cb74f1383860a13daa546] * lisp/apropos.el 
> (apropos-variable): Doc fix.  (Bug#22813).
> 
> masaru@linux-uw5l:/tmp/tes/emacs> make bootstrap -j10
> 
> test  --  NG
> 
> masaru@linux-uw5l:/tmp/tes/emacs> make clean
> 
> masaru@linux-uw5l:/tmp/tes/emacs> git bisect bad
> Bisecting: 0 revisions left to test after this (roughly 0 steps)
> [d2dd614716e34edb5891e58c029741cd6b32217d] Remove unneeded workaround in 
> xftfont.c
> 
> ---------------------------------------------------------------------
> 
> ※ test = Start Emacs & Wanderlust, then try to open the folder in
> Wanderlust. OK means "can open without any problem", NG means "Emacs
> eat 100% CPU).

Thanks, I hope Handa-san will be able to suggest a solution.  Failing
that, the only way out of this mess I can see is introduce a variable
that will control whether we employ that workaround in xftfont.c, and
let users whose fonts need this customize that variable.