Add one more debugging option to see transformation on font-matching

just setting FC_MATCH=3 shows a lot of information and hard to keep on track for informamtion
which is really necessary to see. to use this more effectively, added FC_DBG_MATCH_FILTER to
see for what one really want to see. it takes a comma-separated-list of object names.
If you want to see family name only, try like this:

FC_DBG_MATCH_FILTER=family FC_DEBUG=4096 fc-match

debugging output will be filtered out and see family only in the result.

doc/fontconfig-user.sgml

@@ -258,7 +258,7 @@ debugging messages.
   MEMORY         512    Monitor fontconfig memory usage
   CONFIG        1024    Monitor which config files are loaded
   LANGSET       2048    Dump char sets used to construct lang values
-  OBJTYPES      4096    Display message when value typechecks fail
+  MATCH2        4096    Display font-matching transformation in patterns
   </programlisting>
   <para>
 Add the value of the desired debug levels together and assign that (in
@@ -787,6 +787,10 @@ is used to override the default configuration directory.
 is used to output the detailed debugging messages. see <link linkend="debug">Debugging Applications</link> section for more details.
   </para>
   <para>
+<emphasis>FC_DBG_MATCH_FILTER</emphasis>
+is used to filter out the patterns. this takes a comma-separated list of object names and effects only when FC_DEBUG has MATCH2. see <link linkend="debug">Debugging Applications</link> section for more details.
+  </para>
+  <para>
 <emphasis>FONTCONFIG_USE_MMAP</emphasis>
 is used to control the use of mmap(2) for the cache files if available. this take a boolean value. fontconfig will checks if the cache files are stored on the filesystem that is safe to use mmap(2). explicitly setting this environment variable will causes skipping this check and enforce to use or not use mmap(2) anyway.
   </para>

fontconfig/fontconfig.h

@@ -517,6 +517,9 @@ FcValuePrint (const FcValue v);
 FcPublic void
 FcPatternPrint (const FcPattern *p);
 
+FcPublic void
+FcPatternPrint2 (FcPattern *p1, FcPattern *p2, const FcObjectSet *os);
+
 FcPublic void
 FcFontSetPrint (const FcFontSet *s);
 
@@ -828,6 +831,9 @@ FcPatternEqualSubset (const FcPattern *pa, const FcPattern *pb, const FcObjectSe
 FcPublic FcChar32
 FcPatternHash (const FcPattern *p);
 
+FcPublic int
+FcPatternPosition (const FcPattern *p, const char *object);
+
 FcPublic FcBool
 FcPatternAdd (FcPattern *p, const char *object, FcValue value, FcBool append);
     

src/fcdbg.c

@@ -210,6 +210,84 @@ FcPatternPrint (const FcPattern *p)
 	    printf ("(ignore blanks)");	\
     }
 
+void
+FcPatternPrint2 (FcPattern         *pp1,
+		 FcPattern         *pp2,
+		 const FcObjectSet *os)
+{
+    int i, j, k, pos;
+    FcPatternElt *e1, *e2;
+    FcPattern *p1, *p2;
+
+    if (os)
+    {
+	p1 = FcPatternFilter (pp1, os);
+	p2 = FcPatternFilter (pp2, os);
+    }
+    else
+    {
+	p1 = pp1;
+	p2 = pp2;
+    }
+    printf ("Pattern has %d elts (size %d), %d elts (size %d)\n",
+	    p1->num, p1->size, p2->num, p2->size);
+    for (i = 0, j = 0; i < p1->num; i++)
+    {
+	e1 = &FcPatternElts(p1)[i];
+	e2 = &FcPatternElts(p2)[j];
+	if (e1->object != e2->object)
+	{
+	    pos = FcPatternPosition (p2, FcObjectName (e1->object));
+	    if (pos >= 0)
+	    {
+		for (k = j; k < pos; k++)
+		{
+		    e2 = &FcPatternElts(p2)[k];
+		    printf ("\t%s: (None) -> ", FcObjectName (e2->object));
+		    FcValueListPrint (FcPatternEltValues (e2));
+		    printf ("\n");
+		}
+		j = pos;
+		goto cont;
+	    }
+	    else
+	    {
+		printf ("\t%s:", FcObjectName (e1->object));
+		FcValueListPrint (FcPatternEltValues (e1));
+		printf (" -> (None)\n");
+	    }
+	}
+	else
+	{
+	cont:
+	    printf ("\t%s:", FcObjectName (e1->object));
+	    FcValueListPrint (FcPatternEltValues (e1));
+	    printf (" -> ");
+	    e2 = &FcPatternElts(p2)[j];
+	    FcValueListPrint (FcPatternEltValues (e2));
+	    printf ("\n");
+	    j++;
+	}
+    }
+    if (j < p2->num)
+    {
+	for (k = j; k < p2->num; k++)
+	{
+	    e2 = &FcPatternElts(p2)[k];
+	    if (FcObjectName (e2->object))
+	    {
+		printf ("\t%s: (None) -> ", FcObjectName (e2->object));
+		FcValueListPrint (FcPatternEltValues (e2));
+		printf ("\n");
+	    }
+	}
+    }
+    if (p1 != pp1)
+	FcPatternDestroy (p1);
+    if (p2 != pp2)
+	FcPatternDestroy (p2);
+}
+
 void
 FcOpPrint (FcOp op_)
 {

src/fcint.h

@@ -87,6 +87,7 @@ extern pfnSHGetFolderPathA pSHGetFolderPathA;
 #define FC_DBG_SCANV	256
 #define FC_DBG_CONFIG	1024
 #define FC_DBG_LANGSET	2048
+#define FC_DBG_MATCH2	4096
 
 #define _FC_ASSERT_STATIC1(_line, _cond) typedef int _static_assert_on_line_##_line##_failed[(_cond)?1:-1] FC_UNUSED
 #define _FC_ASSERT_STATIC0(_line, _cond) _FC_ASSERT_STATIC1 (_line, (_cond))

src/fcmatch.c

@@ -689,6 +689,47 @@ FcFontSetMatchInternal (FcFontSet   **sets,
 	printf ("\n");
 	FcPatternPrint (best);
     }
+    if (FcDebug () & FC_DBG_MATCH2)
+    {
+	char *env = getenv ("FC_DBG_MATCH_FILTER");
+	FcObjectSet *os = NULL;
+
+	if (env)
+	{
+	    char *ss, *s;
+	    char *p;
+	    FcBool f = FcTrue;
+
+	    ss = s = strdup (env);
+	    os = FcObjectSetCreate ();
+	    while (f)
+	    {
+		size_t len;
+		char *x;
+
+		if (!(p = strchr (s, ',')))
+		{
+		    f = FcFalse;
+		    len = strlen (s) + 1;
+		}
+		else
+		{
+		    len = (p - s) + 1;
+		}
+		x = malloc (sizeof (char) * len);
+		strncpy (x, s, len - 1);
+		x[len - 1] = 0;
+		if (FcObjectFromName (x) > 0)
+		    FcObjectSetAdd (os, x);
+		s = p + 1;
+		free (x);
+	    }
+	    free (ss);
+	}
+	FcPatternPrint2 (p, best, os);
+	if (os)
+	    FcObjectSetDestroy (os);
+    }
     /* assuming that 'result' is initialized with FcResultNoMatch
      * outside this function */
     if (best)

src/fcpat.c

@@ -425,6 +425,12 @@ FcPatternObjectPosition (const FcPattern *p, FcObject object)
     return -(mid + 1);
 }
 
+int
+FcPatternPosition (const FcPattern *p, const char *object)
+{
+    return FcPatternObjectPosition (p, FcObjectFromName (object));
+}
+
 FcPatternElt *
 FcPatternObjectFindElt (const FcPattern *p, FcObject object)
 {