bug#43148: 27.1; Widget text seems to disappear when building with Cairo and Xaw

[tastytea]

On 2020-12-03 11:13+0900 YAMAMOTO Mitsuharu
<mituharu@math.s.chiba-u.ac.jp> wrote:

> On Tue, 01 Dec 2020 22:10:32 +0900,
> tastytea wrote:
> > 
> > On 2020-11-28 17:22+0900 YAMAMOTO Mitsuharu
> > <mituharu@math.s.chiba-u.ac.jp> wrote:
> >   
> > > On Wed, 25 Nov 2020 11:30:07 +0900,
> > > Basil L. Contovounesios wrote:  
> > > > 
> > > > Robert Pluim <rpluim@gmail.com> writes:
> > > >     
> > > > >>>>>> On Tue, 01 Sep 2020 17:09:18 +0300, Eli Zaretskii
> > > > >>>>>> <eliz@gnu.org> said:    
> > > > >    
> > > > >     >> From: Pouar Dragon <pouar@pouar.net>
> > > > >     >> Date: Mon, 31 Aug 2020 21:34:46 -0500
> > > > >     >> 
> > > > >     >> widgets when building with Xaw and Cairo seem to have
> > > > >     >> missing text, looking like this
> > > > >     >> 
> > > > >     >> problem seems to go away when
> > > > >     >> 5f4e8e2e088de9fb76cb631077c6eddd3219f594 is reverted
> > > > >     >>  
> > > > >    
> > > > >     Eli> Thanks.  I hope Yamamoto-san will be able to take a
> > > > >     Eli> look at this.    
> > > > >
> > > > > Putting on my 'let's simplify' hat, is this really a
> > > > > combination we want to spend time on? Lucid + Xaw + Cairo is
> > > > > decidedly non-mainstream (Iʼm surprised it even builds).    
> > > > 
> > > > FWIW, I've been happily using Lucid + Xaw3D for several years,
> > > > and Cairo ever since it became stable in Emacs 27 and the
> > > > default configuration in Emacs 28.
> > > > 
> > > > I usually have menu-bar-mode off, but like other reports in this
> > > > thread, the menus look fine when I do open them, e.g. after
> > > > 'emacs -Q'.
> > > > 
> > > > Could the issue depend on e.g. the version of Cairo?  (I seem to
> > > > have an older version than the OP.)    
> > > 
> > > Possibly.  The OP seems to use cairo 1.17.3, which is not a
> > > release version (the latest is 1.16.0) and even not the snapshot
> > > one (the latest is 1.17.2 according to
> > > https://cairographics.org).  
> > 
> > I experience the same issue as the OP with lucid and cairo 1.16.0,
> > with and without xaw3d, on Gentoo Linux. The problem goes away if I
> > disable cairo.
> > The same happens with 28.0.50, commit
> > 1a3aa6043a51e5bb4007889dd7dcabb55dc44132.  
> 
> So, only digits are shown with "$ emacs -Q" ?

Yes, exactly like the screenshot in the first message.

> Could you show us the output of "$ fc-match -s sans" ?
> 
> I tried the latest snapshot cairo 1.17.4 on XQuartz/macOS, and I don't
> see any problems.  On my side, "$ fc-match -s sans" reports Arial
> Unicode.ttf at the first line.

The list is huge, are the first 10 lines enough?

SourceSansPro-Regular.otf: "Source Sans Pro" "Regular"
NotoColorEmoji.ttf: "Noto Color Emoji" "Regular"
LiberationSans-Regular.ttf: "Liberation Sans" "Regular"
DejaVuSans.ttf: "DejaVu Sans" "Book"
DejaVuSans-Bold.ttf: "DejaVu Sans" "Bold"
DejaVuSans-Oblique.ttf: "DejaVu Sans" "Oblique"
DejaVuSans-BoldOblique.ttf: "DejaVu Sans" "Bold Oblique"
luxisr.ttf: "Luxi Sans" "Regular"
l048013t.pfa: "Luxi Sans" "Regular"
n019003l.pfb: "Nimbus Sans L" "Regular"

When I saw that the first entry is an OTF font I remembered that I
configured Emacs --without-libotf, so I enabled the m17n-lib useflag
which enables --with-libotf --with-m17n-flt, but that didn't change
anything.
I also set 
  Emacs*font: DejaVu Sans Regular-12
in ~/.Xresources, but that didn't help either.