master 38e2291cce0: Fix merging italic and underline faces with other fonts

[Eli Zaretskii]

branch: master
commit 38e2291cce0e396dcb6f379cf74471ab9504522b
Author: Eli Zaretskii <eliz@gnu.org>
Commit: Eli Zaretskii <eliz@gnu.org>

    Fix merging italic and underline faces with other fonts
    
    * lisp/faces.el (italic, underline): Leave the 'slant'
    resp. 'underline' attributes even when they are not supported by
    the default font.  (Bug#67269)
---
 lisp/faces.el | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/lisp/faces.el b/lisp/faces.el
index 7eacc40443a..8eaabbffc0e 100644
--- a/lisp/faces.el
+++ b/lisp/faces.el
@@ -2440,7 +2440,10 @@ If you set `term-file-prefix' to nil, this function does 
nothing."
   '((((supports :slant italic))
      :slant italic)
     (((supports :underline t))
-     :underline t)
+     ;; Include italic, even if it isn't supported by the default
+     ;; font, because this face could be merged with another face
+     ;; which uses font that does have an italic variant.
+     :underline t :slant italic)
     (t
      ;; Default to italic, even if it doesn't appear to be supported,
      ;; because in some cases the display engine will do its own
@@ -2457,7 +2460,9 @@ If you set `term-file-prefix' to nil, this function does 
nothing."
 (defface underline
   '((((supports :underline t))
      :underline t)
-    (((supports :weight bold))
+    ;; Include underline, for when this face is merged with another
+    ;; whose font does support underline.
+    (((supports :weight bold :underline t))
      :weight bold)
     (t :underline t))
   "Basic underlined face."