bug#37473: 27.0.50; antialias setting is not preserved by, inheriting

[David Ponce]

Hello,

The below related today's commit to xface.c breaks antialiasing:

From b2d11d69dd49864874f8fe53669b4049e83bfce9 Mon Sep 17 00:00:00 2001
From: Po Lu <luangruo@yahoo.com>
Date: Sun, 19 Jun 2022 21:57:11 +0800
Subject: More conservative fix for bug#37473

* src/xfaces.c (realize_gui_face): Add more conservative fix,
since the last change makes C-x C-+ lead to weight weirdness on
my machine.
---
 src/xfaces.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/src/xfaces.c b/src/xfaces.c
index 4242205..25b5e4d 100644
--- a/src/xfaces.c
+++ b/src/xfaces.c
@@ -5909,7 +5909,7 @@ realize_gui_face (struct face_cache *cache, 
Lisp_Object attrs[LFACE_VECTOR_SIZE]
 #ifdef HAVE_WINDOW_SYSTEM
   struct face *default_face;
   struct frame *f;
-  Lisp_Object stipple, underline, overline, strike_through, box;
+  Lisp_Object stipple, underline, overline, strike_through, box, temp_spec;

   eassert (FRAME_WINDOW_P (cache->f));

@@ -5953,17 +5953,18 @@ realize_gui_face (struct face_cache *cache, 
Lisp_Object attrs[LFACE_VECTOR_SIZE]
       if (! FONT_OBJECT_P (attrs[LFACE_FONT_INDEX]))
        {
          /* We want attrs to allow overriding most elements in the
-            spec, but we don't want to start with an all-nil font,
-            either, because then we lose attributes like
-            antialiasing.  This should probably be fixed in a
-            different way, see bug#17973 and bug#37473.  */
-         Lisp_Object spec = copy_font_spec (attrs[LFACE_FONT_INDEX]);
-         Ffont_put (spec, QCfoundry, Qnil);
-         Ffont_put (spec, QCfamily, Qnil);
-         Ffont_put (spec, QCregistry, Qnil);
-         Ffont_put (spec, QCadstyle, Qnil);
+            spec (IOW, to start out as an empty font spec), but
+            preserve the antialiasing attribute.  (bug#17973,
+            bug#37473).  */
+         temp_spec = Ffont_spec (0, NULL);
+
+         if (FONTP (attrs[LFACE_FONT_INDEX]))
+           Ffont_put (temp_spec, QCantialias,
+                      Ffont_get (attrs[LFACE_FONT_INDEX],
+                                 QCantialias));
+
          attrs[LFACE_FONT_INDEX]
-           = font_load_for_lface (f, attrs, spec);
+           = font_load_for_lface (f, attrs, temp_spec);
        }
       if (FONT_OBJECT_P (attrs[LFACE_FONT_INDEX]))
        {
--
cgit v1.1


The below marked line seems not correct. According to the previous 
condition "if (! FONT_OBJECT_P (attrs[LFACE_FONT_INDEX]))", it should 
always be false, so the antialising attibute is never preserved:

          if (FONTP (attrs[LFACE_FONT_INDEX])) <=====================
            Ffont_put (temp_spec, QCantialias,
                       Ffont_get (attrs[LFACE_FONT_INDEX],
                                  QCantialias));

Thanks,
David Ponce