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>]

On 2020-12-05 15:51+0900 YAMAMOTO Mitsuharu
<mituharu@math.s.chiba-u.ac.jp> wrote:

> On Fri, 04 Dec 2020 18:28:24 +0900,
> tastytea wrote:
> > 
> > [1  <text/plain; UTF-8 (quoted-printable)>]
> > 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:  
> 
> I could reproduce the problem with your configuration.
> Could you try the patch below?

Yes! Thanks, that worked. :-)