Add FC_FONT_WRAPPER

Currently detects only SFNT wrappers:
- WOFF: if it is FreeType says it is an SFNT font the file starts with wOFF tag
- WOFF2: the same but tag is wOF2
- SFNT: for any other SFNT font (which helps distinguishing standalone
  CFF fonts from CFF in SFNT aka OTF)

Fixes #375

doc/fontconfig-devel.sgml

@@ -216,6 +216,7 @@ convenience for the application's rendering mechanism.
     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
+    fontwarapper   FC_FONT_WRAPPER        String  The font wrapper format
     </programlisting>
   </sect2>
 </sect1>

doc/fontconfig-user.sgml

@@ -148,6 +148,8 @@ 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
+fontwarapper    String  The font wrapper format, current values are WOFF, WOFF2,
+                        and SFNT for any other SFNT font.
     </programlisting>
   </refsect2>
   <refsect2>

fontconfig/fontconfig.h

@@ -130,6 +130,7 @@ typedef int		FcBool;
 #define FC_ORDER	    "order"		/* Integer */
 #define FC_DESKTOP_NAME     "desktop"		/* String */
 #define FC_NAMED_INSTANCE   "namedinstance"	/* Bool - true if font is named instance */
+#define FC_FONT_WRAPPER     "fontwrapper" 	/* String */
 
 #define FC_CACHE_SUFFIX		    ".cache-" FC_CACHE_VERSION
 #define FC_DIR_CACHE_FILE	    "fonts.cache-" FC_CACHE_VERSION

src/fcfreetype.c

@@ -27,6 +27,7 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
+#include <fcntl.h>
 #include <ft2build.h>
 #include FT_FREETYPE_H
 #include FT_ADVANCES_H
@@ -2178,6 +2179,30 @@ FcFreeTypeQueryFaceInternal (const FT_Face  face,
     if (!FcPatternObjectAddBool (pat, FC_NAMED_INSTANCE_OBJECT, !!(id > 0xffff)))
 	    goto bail2;
 
+    if (face->face_flags & FT_FACE_FLAG_SFNT)
+    {
+	/* If this is an SFNT wrapper, try to sniff the SFNT tag which is the
+	 * first 4 bytes, to see if it is a WOFF or WOFF2 wrapper. */
+	FcChar8* wrapper = (FcChar8*) "SFNT";
+
+	char buf[4];
+	int fd = FcOpen ((char *) file, O_RDONLY);
+	if (fd != -1 && read (fd, buf, 4))
+	{
+	    if (buf[0] == 'w' && buf[1] == 'O' && buf[2] == 'F')
+	    {
+		if (buf[3] == 'F')
+		    wrapper = (FcChar8*) "WOFF";
+		else if (buf[3] == '2')
+		    wrapper = (FcChar8*) "WOFF2";
+	    }
+	}
+	close (fd);
+
+	if (!FcPatternObjectAddString (pat, FC_FONT_WRAPPER_OBJECT, wrapper))
+	    goto bail2;
+    }
+
     /*
      * Drop our reference to the charset
      */

src/fcmatch.c

@@ -322,6 +322,7 @@ typedef enum _FcMatcherPriorityDummy {
 
 typedef enum _FcMatcherPriority {
     PRI1(FILE),
+    PRI1(FONT_WRAPPER),
     PRI1(FONTFORMAT),
     PRI1(VARIABLE),
     PRI1(NAMED_INSTANCE),

src/fcobjs.h

@@ -76,4 +76,5 @@ FC_OBJECT (FONT_HAS_HINT,	FcTypeBool,	FcCompareBool)
 FC_OBJECT (ORDER,		FcTypeInteger,	FcCompareNumber)
 FC_OBJECT (DESKTOP_NAME,	FcTypeString,	NULL)
 FC_OBJECT (NAMED_INSTANCE,	FcTypeBool,	FcCompareBool)
+FC_OBJECT (FONT_WRAPPER,	FcTypeString,	FcCompareString)
 /* ^-------------- Add new objects here. */