bug#49722: 27.2; Emacs won't build with old versions of fontconfig

bug#49722: 27.2; Emacs won't build with old versions of fontconfig

[Andrei Kuznetsov]

I was unable to build Emacs 27.2 on a system with some old version
(2.5.0) of fontconfig without applying the following patch:

diff -u a/emacs-27.2/src/xftfont.c b/emacs-27.2/src/xftfont.c
--- a/emacs-27.2/src/xftfont.c
+++ b/emacs-27.2/src/xftfont.c
@@ -588,8 +588,10 @@
   r1 = FcPatternGetInteger (pat, FC_HINT_STYLE, 0, &i1);
   r2 = FcPatternGetInteger (oldpat, FC_HINT_STYLE, 0, &i2);
   if (r1 != r2 || i1 != i2) goto out;
+#ifdef FC_LCD_FILTER
   r1 = FcPatternGetInteger (pat, FC_LCD_FILTER, 0, &i1);
   r2 = FcPatternGetInteger (oldpat, FC_LCD_FILTER, 0, &i2);
+#endif
   if (r1 != r2 || i1 != i2) goto out;
   r1 = FcPatternGetInteger (pat, FC_RGBA, 0, &i1);
   r2 = FcPatternGetInteger (oldpat, FC_RGBA, 0, &i2);

Diff finished.  Sat Jul 24 14:26:32 2021

The system on which the bug was discovered runs Fedora Core 9, but it
should be reproducible by building Emacs with Xft on a system with
fontconfig older than 2.6.0 (and possibly newer -- I am not sure on
that).

In GNU Emacs 27.2 (build 1, powerpc-unknown-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2021-07-24 built on distributor-machine
Windowing system distributor 'The X.Org Foundation', version 11.0.12101001
System Description: Fedora release 9 (Sulphur)

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Configured using:
 'configure --prefix=/usr/local --with-gnutls=no'

Configured features:
XAW3D XPM JPEG TIFF GIF PNG RSVG SOUND GPM DBUS GCONF GLIB ACL
LIBSELINUX LIBXML2 FREETYPE XFT ZLIB TOOLKIT_SCROLL_BARS LUCID X11 XDBE
XIM MODULES THREADS PDUMPER

Important settings:
  value of $LANG: en_GB.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny dired dired-loaddefs
format-spec rfc822 mml easymenu mml-sec password-cache epa derived epg
epg-config gnus-util rmail rmail-loaddefs text-property-search seq
byte-opt gv bytecomp byte-compile cconv mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils time-date subr-x
cl-loaddefs cl-lib tooltip eldoc electric uniquify ediff-hook vc-hooks
lisp-float-type mwheel term/x-win x-win term/common-win x-dnd tool-bar
dnd fontset image regexp-opt fringe tabulated-list replace newcomment
text-mode elisp-mode lisp-mode prog-mode register page tab-bar menu-bar
rfn-eshadow isearch timer select scroll-bar mouse jit-lock font-lock
syntax facemenu font-core term/tty-colors frame minibuffer cl-generic
cham georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech
european ethiopic indian cyrillic chinese composite charscript charprop
case-table epa-hook jka-cmpr-hook help simple abbrev obarray
cl-preloaded nadvice loaddefs button faces cus-face macroexp files
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote threads dbusbind
dynamic-setting system-font-setting font-render-setting x-toolkit x
multi-tty make-network-process emacs)

Memory information:
((conses 8 44357 8801)
 (symbols 24 5958 1)
 (strings 16 16066 1889)
 (string-bytes 1 512783)
 (vectors 8 9285)
 (vector-slots 4 137016 13736)
 (floats 8 21 50)
 (intervals 28 202 7)
 (buffers 576 11)
 (heap 1024 3934 455))

bug#49722: 27.2; Emacs won't build with old versions of fontconfig

[Eli Zaretskii]

> From: Andrei Kuznetsov <r12451428287@163.com>
> Date: Sat, 24 Jul 2021 18:01:03 +0800
> 
> I was unable to build Emacs 27.2 on a system with some old version
> (2.5.0) of fontconfig without applying the following patch:

Thanks, but please show the error messages you saw before applying
that patch.

bug#49722: 27.2; Emacs won't build with old versions of fontconfig

[Andrei Kuznetsov]

Eli Zaretskii <eliz@gnu.org> writes:

> Thanks, but please show the error messages you saw before applying
> that patch.

xftfont.c: In function ‘xftfont_cached_font_ok’:
xftfont.c:591: error: ‘FC_LCD_FILTER’ undeclared (first use in this function)
xftfont.c:591: error: (Each undeclared identifier is reported only once
xftfont.c:591: error: for each function it appears in.)

It appears that FC_LCD_FILTER is not present on these older versions of
fontconfig.

bug#49722: 27.2; Emacs won't build with old versions of fontconfig

[Eli Zaretskii]

> From: Andrei Kuznetsov <r12451428287@163.com>
> Cc: 49722@debbugs.gnu.org
> Date: Sun, 25 Jul 2021 08:53:59 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Thanks, but please show the error messages you saw before applying
> > that patch.
> 
> xftfont.c: In function ‘xftfont_cached_font_ok’:
> xftfont.c:591: error: ‘FC_LCD_FILTER’ undeclared (first use in this function)
> xftfont.c:591: error: (Each undeclared identifier is reported only once
> xftfont.c:591: error: for each function it appears in.)
> 
> It appears that FC_LCD_FILTER is not present on these older versions of
> fontconfig.

Thanks.  We once had the following in xftfont.c:

  #ifndef FC_LCD_FILTER
    /* Older fontconfig versions don't have FC_LCD_FILTER. */
  #define FC_LCD_FILTER "lcdfilter"
  #endif

But it got moved to ftfont.c when a function which used it was moved
there.  However, since xftfont.c still uses this, I think we should
have this #define in xftfont.c as well, so please try adding that at
the beginning of xftfont.c, and see if that helps.

bug#49722: 27.2; Emacs won't build with old versions of fontconfig

[Andrei Kuznetsov]

Eli Zaretskii <eliz@gnu.org> writes:

> However, since xftfont.c still uses this, I think we should
> have this #define in xftfont.c as well, so please try adding that at
> the beginning of xftfont.c, and see if that helps.

Indeed it does.  With the aformentioned change, Emacs now builds and
seems to operate normally.

bug#49722: 27.2; Emacs won't build with old versions of fontconfig

[Stefan Kangas]

close 49722 28.1
thanks

Eli Zaretskii <eliz@gnu.org> writes:

>> xftfont.c: In function ‘xftfont_cached_font_ok’:
>> xftfont.c:591: error: ‘FC_LCD_FILTER’ undeclared (first use in this function)
>> xftfont.c:591: error: (Each undeclared identifier is reported only once
>> xftfont.c:591: error: for each function it appears in.)
>>
>> It appears that FC_LCD_FILTER is not present on these older versions of
>> fontconfig.
>
> Thanks.  We once had the following in xftfont.c:
>
>   #ifndef FC_LCD_FILTER
>     /* Older fontconfig versions don't have FC_LCD_FILTER. */
>   #define FC_LCD_FILTER "lcdfilter"
>   #endif
>
> But it got moved to ftfont.c when a function which used it was moved
> there.  However, since xftfont.c still uses this, I think we should
> have this #define in xftfont.c as well, so please try adding that at
> the beginning of xftfont.c, and see if that helps.

Andrei Kuznetsov <r12451428287@163.com> writes:

> Indeed it does.  With the aformentioned change, Emacs now builds and
> seems to operate normally.

The fix was installed, so I'm closing this bug report.

commit 41a55a330f518254da795719ac6e3085254d4110
Author: Eli Zaretskii <eliz@gnu.org>
Date:   Sun Jul 25 15:50:46 2021 +0300

    Fix compilation of xftfont.c with old fontconfig

    * src/xftfont.c (FC_LCD_FILTER): Define if undefined, for older
    versions of fontconfig.  This was mistakenly deleted 2 years ago.
    (Bug#49722)