Support font driver supersession

* src/font.c (font_update_drivers): If argument NEW_DRIVERS is t, then don't
use superseded drivers.
(syms_of_font) <Qfont_driver_superseded_by>: New DEFSYM.

* src/ftfont.c (syms_of_ftfont) [HAVE_HARFBUZZ]:
* src/ftcrfont.c (syms_of_ftcrfont) [HAVE_HARFBUZZ]:
* src/w32font.c (syms_of_w32font) [HAVE_HARFBUZZ]:
* src/xftfont.c (syms_of_xftfont) [HAVE_HARFBUZZ]: Make Harfbuzz variants
supersede non-Harfbuzz ones.

* src/w32fns.c (Fx_create_frame, w32_create_tip_frame): Remove font backend
determination code.

1 files changed, 4 insertions, 76 deletions

diff --git a/src/w32fns.c b/src/w32fns.c
index 8ebfc119521..83830c616e5 100644
--- a/src/w32fns.c
+++ b/src/w32fns.c
@@ -5844,46 +5844,10 @@ DEFUN ("x-create-frame", Fx_create_frame, Sx_create_frame,
       specbind (Qx_resource_name, name);
     }
 
-  bool register_uniscribe = uniscribe_available;
 #ifdef HAVE_HARFBUZZ
-  /* Register Uniscribe only if HarfBuzz is not available or if
-     explicitly requested.  If Uniscribe is registered, register
-     HarfBuzz only if explicitly requested.  */
-  bool register_harfbuzz = harfbuzz_available;
-  if (register_harfbuzz)
-    register_uniscribe = false;
-  Lisp_Object dflt_backends
-    = gui_display_get_arg (dpyinfo, parameters, Qfont_backend,
-			   "fontBackend", "FontBackend", RES_TYPE_STRING);
-  if (!EQ (dflt_backends, Qunbound))
-    {
-      bool harfbuzz_requested = false, uniscribe_requested = false;
-      if (CONSP (dflt_backends))
-	{
-	  if (!NILP (Fmemq (Quniscribe, dflt_backends)))
-	    uniscribe_requested = true;
-	  if (!NILP (Fmemq (Qharfbuzz, dflt_backends)))
-	    harfbuzz_requested = true;
-	}
-      else if (STRINGP (dflt_backends))
-	{
-	  if (strcmp (SSDATA (dflt_backends), "uniscribe") == 0)
-	    uniscribe_requested = true;
-	  else if (strcmp (SSDATA (dflt_backends), "harfbuzz") == 0)
-	    harfbuzz_requested = true;
-	}
-      if (uniscribe_requested)
-	{
-	  register_uniscribe = uniscribe_available;
-	  if (!harfbuzz_requested)
-	    register_harfbuzz = false;
-	}
-    }
-  if (register_harfbuzz)
-    register_font_driver (&harfbuzz_font_driver, f);
+  register_font_driver (&harfbuzz_font_driver, f);
 #endif
-  if (register_uniscribe)
-    register_font_driver (&uniscribe_font_driver, f);
+  register_font_driver (&uniscribe_font_driver, f);
   register_font_driver (&w32font_driver, f);
 
   gui_default_parameter (f, parameters, Qfont_backend, Qnil,
@@ -6935,46 +6899,10 @@ w32_create_tip_frame (struct w32_display_info *dpyinfo, Lisp_Object parms)
       specbind (Qx_resource_name, name);
     }
 
-  bool register_uniscribe = uniscribe_available;
 #ifdef HAVE_HARFBUZZ
-  /* Register Uniscribe only if HarfBuzz is not available or if
-     explicitly requested.  If Uniscribe is registered, register
-     HarfBuzz only if explicitly requested.  */
-  bool register_harfbuzz = harfbuzz_available;
-  if (register_harfbuzz)
-    register_uniscribe = false;
-  Lisp_Object dflt_backends
-    = gui_display_get_arg (dpyinfo, parms, Qfont_backend,
-			   "fontBackend", "FontBackend", RES_TYPE_STRING);
-  if (!EQ (dflt_backends, Qunbound))
-    {
-      bool harfbuzz_requested = false, uniscribe_requested = false;
-      if (CONSP (dflt_backends))
-	{
-	  if (!NILP (Fmemq (Quniscribe, dflt_backends)))
-	    uniscribe_requested = true;
-	  if (!NILP (Fmemq (Qharfbuzz, dflt_backends)))
-	    harfbuzz_requested = true;
-	}
-      else if (STRINGP (dflt_backends))
-	{
-	  if (strcmp (SSDATA (dflt_backends), "uniscribe") == 0)
-	    uniscribe_requested = true;
-	  else if (strcmp (SSDATA (dflt_backends), "harfbuzz") == 0)
-	    harfbuzz_requested = true;
-	}
-      if (uniscribe_requested)
-	{
-	  register_uniscribe = uniscribe_available;
-	  if (!harfbuzz_requested)
-	    register_harfbuzz = false;
-	}
-    }
-  if (register_harfbuzz)
-    register_font_driver (&harfbuzz_font_driver, f);
+  register_font_driver (&harfbuzz_font_driver, f);
 #endif
-  if (register_uniscribe)
-    register_font_driver (&uniscribe_font_driver, f);
+  register_font_driver (&uniscribe_font_driver, f);
   register_font_driver (&w32font_driver, f);
 
   gui_default_parameter (f, parms, Qfont_backend, Qnil,