Add namedinstance property

This change allows applications to detect if a font
is a variable font and a named-instance.
If they are, namedinstance property is set to true,
otherwise false.

Fixes https://gitlab.freedesktop.org/fontconfig/fontconfig/-/issues/362

doc/fontconfig-devel.sgml

@@ -215,6 +215,7 @@ convenience for the application's rendering mechanism.
     fonthashint    FC_FONT_HAS_HINT       Bool    Whether font has hinting
     order          FC_ORDER               Int     Order number of the font
     desktop        FC_DESKTOP_NAME        String  Current desktop name
+    namedinstance  FC_NAMED_INSTANCE      Bool    Whether font is a named-instance
     </programlisting>
   </sect2>
 </sect1>

doc/fontconfig-user.sgml

@@ -147,6 +147,7 @@ variable        Bool    Wheter font is Variable Font
 fonthashint     Bool    Whether the font has hinting
 order           Int     Order number of the font
 desktop         String  Current desktop name
+namedinstance   Bool    Whether font is a named-instance
     </programlisting>
   </refsect2>
   <refsect2>

fontconfig/fontconfig.h

@@ -129,6 +129,7 @@ typedef int		FcBool;
 #define FC_FONT_HAS_HINT    "fonthashint"	/* Bool - true if font has hinting */
 #define FC_ORDER	    "order"		/* Integer */
 #define FC_DESKTOP_NAME     "desktop"		/* String */
+#define FC_NAMED_INSTANCE   "namedinstance"	/* Bool - true if font is namedinstance */
 
 #define FC_CACHE_SUFFIX		    ".cache-" FC_CACHE_VERSION
 #define FC_DIR_CACHE_FILE	    "fonts.cache-" FC_CACHE_VERSION

src/fcfreetype.c

@@ -2175,6 +2175,8 @@ FcFreeTypeQueryFaceInternal (const FT_Face  face,
 		goto bail2;
     }
 #endif
+    if (!FcPatternObjectAddBool (pat, FC_NAMED_INSTANCE_OBJECT, !!(id > 0xffff)))
+	    goto bail2;
 
     /*
      * Drop our reference to the charset

src/fcmatch.c

@@ -324,6 +324,7 @@ typedef enum _FcMatcherPriority {
     PRI1(FILE),
     PRI1(FONTFORMAT),
     PRI1(VARIABLE),
+    PRI1(NAMED_INSTANCE),
     PRI1(SCALABLE),
     PRI1(COLOR),
     PRI1(FOUNDRY),

src/fcobjs.h

@@ -75,4 +75,5 @@ FC_OBJECT (VARIABLE,		FcTypeBool,	FcCompareBool)
 FC_OBJECT (FONT_HAS_HINT,	FcTypeBool,	FcCompareBool)
 FC_OBJECT (ORDER,		FcTypeInteger,	FcCompareNumber)
 FC_OBJECT (DESKTOP_NAME,	FcTypeString,	NULL)
+FC_OBJECT (NAMED_INSTANCE,	FcTypeBool,	FcCompareBool)
 /* ^-------------- Add new objects here. */

test/test-namedinstance.json

@@ -0,0 +1,64 @@
+{
+    "fonts": [
+        {
+            "family": [
+                "Foo"
+            ],
+            "style": [
+                "Regular"
+            ],
+            "file": "/path/to/Foo-VF.otf",
+            "index": 1,
+            "namedinstance": false,
+            "fontversion": 1
+        },
+        {
+            "family": [
+                "Foo",
+                "Foo Bold"
+            ],
+            "style": [
+                "Bold",
+                "Regular"
+            ],
+            "file": "/path/to/Foo-VF.otf",
+            "index": 65537,
+            "namedinstance": true,
+            "fontversion": 1
+        }
+    ],
+    "tests": [
+        {
+            "method": "match",
+            "query": {
+                "family": "Foo",
+                "style": "Bold",
+                "namedinstance": false
+            },
+            "result": {
+                "family": "Foo",
+                "style": "Regular",
+                "file": "/path/to/Foo-VF.otf",
+                "index": 1,
+                "namedinstance": false,
+                "fontversion": 1
+            }
+        },
+        {
+            "method": "match",
+            "query": {
+                "family": "Foo",
+                "style": "Bold",
+                "namedinstance": true
+            },
+            "result": {
+                "family": "Foo",
+                "style": "Bold",
+                "file": "/path/to/Foo-VF.otf",
+                "index": 65537,
+                "namedinstance": true,
+                "fontversion": 1
+            }
+        }
+    ]
+}