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

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

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On 2020-12-04 17:41+0900 YAMAMOTO Mitsuharu
<mituharu@math.s.chiba-u.ac.jp> wrote:

> On Thu, 03 Dec 2020 17:18:15 +0900,
> tastytea wrote:
> > 
> > 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
> > > > > > >     Eli> take a 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"  
> 
> Thanks.  I conjectured Noto Color Emoji, which contains digit glyphs
> but not for letter ones, would come first.  But that is not the case.
> I don't know why Source Sans Pro is not used then (libotf is for
> handling OTF features and not necessary just for displaying).
> 
> Anyway, could you try if the following patch works?

With the patch I get rectangles instead of letters.

I removed Noto Color Emoji from my font configuration in
~/.config/fontconfig/fonts.conf and that did the trick. The menus are
showing text now with and without the patch. But I have no idea why,
all other programs work fine with that configuration:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
  <!-- Prefer Noto's Color Emoji Font -->
  <alias>
    <family>serif</family>
    <prefer>
      <family>Noto Color Emoji</family>
    </prefer>
  </alias>
  <alias>
    <family>sans-serif</family>
    <prefer>
      <family>Noto Color Emoji</family>
    </prefer>
  </alias>
  <alias>
    <family>monospace</family>
    <prefer>
      <family>Noto Color Emoji</family>
    </prefer>
  </alias>

  <!-- Set default fonts -->
  <alias>
    <family>monospace</family>
    <prefer>
      <family>Source Code Pro</family>
    </prefer>
  </alias>
  <alias>
    <family>serif</family>
    <prefer>
      <family>Source Serif Pro</family>
    </prefer>
  </alias>
  <alias>
    <family>sans-serif</family>
    <prefer>
      <family>Source Sans Pro</family>
    </prefer>
  </alias>
</fontconfig>

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