Take effect sysroot functionality to the default config file

When loading the default config file with FONTCONFIG_SYSROOT,
it fails if no /etc/fonts/fonts.conf is available, even if it is
there where is based on sysroot.

To address this, FcConfig is required to determine the sysroot.
therefore, this change makes FcConfigFilename() deprecated,
use FcConfigGetFilename() instead.

Fixes https://gitlab.freedesktop.org/fontconfig/fontconfig/issues/181

doc/fcconfig.fncs

@@ -344,6 +344,15 @@ to be up to date, and used.
 @TYPE1@         const FcChar8 *			@ARG1@          name
 @PURPOSE@	Find a config file
 @DESC@
+This function is deprecated and is replaced by <function>FcConfigGetFilename</function>.
+@@
+
+@RET@           FcChar8 *
+@FUNC@          FcConfigGetFilename
+@TYPE1@         FcConfig *			@ARG1@          config
+@TYPE2@         const FcChar8 *			@ARG2@          name
+@PURPOSE@	Find a config file
+@DESC@
 Given the specified external entity name, return the associated filename.
 This provides applications a way to convert various configuration file
 references into filename form.
@@ -355,6 +364,8 @@ refers to a file in the current users home directory.  Otherwise if the name
 doesn't start with '/', it refers to a file in the default configuration
 directory; the built-in default directory can be overridden with the
 FONTCONFIG_PATH environment variable.
+    </para><para>
+The result of this function is affected by the FONTCONFIG_SYSROOT environment variable or equivalent functionality.
 @@
 
 @RET@		FcBool

fontconfig/fontconfig.h

@@ -393,6 +393,10 @@ FcConfigHome (void);
 FcPublic FcBool
 FcConfigEnableHome (FcBool enable);
 
+FcPublic FcChar8 *
+FcConfigGetFilename (FcConfig      *config,
+		     const FcChar8 *url);
+
 FcPublic FcChar8 *
 FcConfigFilename (const FcChar8 *url);
     

src/fccfg.c

@@ -686,7 +686,7 @@ FcConfigAddConfigFile (FcConfig	    *config,
 		       const FcChar8   *f)
 {
     FcBool	ret;
-    FcChar8	*file = FcConfigFilename (f);
+    FcChar8	*file = FcConfigGetFilename (config, f);
 
     if (!file)
 	return FcFalse;
@@ -2284,10 +2284,19 @@ FcConfigEnableHome (FcBool enable)
 }
 
 FcChar8 *
-FcConfigFilename (const FcChar8 *url)
+FcConfigGetFilename (FcConfig      *config,
+		     const FcChar8 *url)
 {
     FcChar8    *file, *dir, **path, **p;
+    const FcChar8 *sysroot;
 
+    if (!config)
+    {
+	config = FcConfigGetCurrent ();
+	if (!config)
+	    return NULL;
+    }
+    sysroot = FcConfigGetSysRoot (config);
     if (!url || !*url)
     {
 	url = (FcChar8 *) getenv ("FONTCONFIG_FILE");
@@ -2297,13 +2306,23 @@ FcConfigFilename (const FcChar8 *url)
     file = 0;
 
     if (FcStrIsAbsoluteFilename(url))
-	return FcConfigFileExists (0, url);
+	return FcConfigFileExists (sysroot, url);
 
     if (*url == '~')
     {
 	dir = FcConfigHome ();
 	if (dir)
-	    file = FcConfigFileExists (dir, url + 1);
+	{
+	    FcChar8 *s;
+
+	    if (sysroot)
+		s = FcStrBuildFilename (sysroot, dir, NULL);
+	    else
+		s = dir;
+	    file = FcConfigFileExists (s, url + 1);
+	    if (sysroot)
+		FcStrFree (s);
+	}
 	else
 	    file = 0;
     }
@@ -2314,7 +2333,15 @@ FcConfigFilename (const FcChar8 *url)
 	    return NULL;
 	for (p = path; *p; p++)
 	{
-	    file = FcConfigFileExists (*p, url);
+	    FcChar8 *s;
+
+	    if (sysroot)
+		s = FcStrBuildFilename (sysroot, *p, NULL);
+	    else
+		s = *p;
+	    file = FcConfigFileExists (s, url);
+	    if (sysroot)
+		FcStrFree (s);
 	    if (file)
 		break;
 	}
@@ -2323,33 +2350,31 @@ FcConfigFilename (const FcChar8 *url)
     return file;
 }
 
+FcChar8 *
+FcConfigFilename (const FcChar8 *url)
+{
+    return FcConfigGetFilename (NULL, url);
+}
+
 FcChar8 *
 FcConfigRealFilename (FcConfig		*config,
 		      const FcChar8	*url)
 {
-    const FcChar8 *sysroot = FcConfigGetSysRoot (config);
+    FcChar8 *n = FcConfigGetFilename (config, url);
-    FcChar8 *n = FcConfigFilename (url);
-    FcChar8 *nn = NULL;
 
     if (n)
     {
 	FcChar8 buf[FC_PATH_MAX];
 	ssize_t len;
 
-	if (sysroot)
+	if ((len = FcReadLink (n, buf, sizeof (buf) - 1)) != -1)
-	    nn = FcStrBuildFilename (sysroot, n, NULL);
-	else
-	    nn = FcStrdup (n);
-	FcStrFree (n);
-
-	if ((len = FcReadLink (nn, buf, sizeof (buf) - 1)) != -1)
 	{
 	    buf[len] = 0;
 
 	    if (!FcStrIsAbsoluteFilename (buf))
 	    {
-		FcChar8 *dirname = FcStrDirname (nn);
+		FcChar8 *dirname = FcStrDirname (n);
-		FcStrFree (nn);
+		FcStrFree (n);
 		if (!dirname)
 		    return NULL;
 
@@ -2358,18 +2383,18 @@ FcConfigRealFilename (FcConfig		*config,
 		if (!path)
 		    return NULL;
 
-		nn = FcStrCanonFilename (path);
+		n = FcStrCanonFilename (path);
 		FcStrFree (path);
 	    }
 	    else
 	    {
-		FcStrFree (nn);
+		FcStrFree (n);
-		nn = FcStrdup (buf);
+		n = FcStrdup (buf);
 	    }
 	}
     }
 
-    return nn;
+    return n;
 }
 
 /*

src/fcxml.c

@@ -2541,7 +2541,7 @@ FcParseInclude (FcConfigParse *parse)
         FcChar8 *filename;
 	static FcBool warn_conf = FcFalse, warn_confd = FcFalse;
 
-        filename = FcConfigFilename(s);
+        filename = FcConfigGetFilename(parse->config, s);
 	if (deprecated == FcTrue &&
 	    filename != NULL &&
 	    userdir != NULL &&
@@ -3532,7 +3532,9 @@ _FcConfigParse (FcConfig	*config,
     FcStrBuf	    sbuf;
     char            buf[BUFSIZ];
     FcBool	    ret = FcFalse, complain_again = complain;
+    FcStrBuf	    reason;
 
+    FcStrBufInit (&reason, NULL, 0);
 #ifdef _WIN32
     if (!pGetSystemWindowsDirectory)
     {
@@ -3549,12 +3551,20 @@ _FcConfigParse (FcConfig	*config,
     }
 #endif
 
-    filename = FcConfigFilename (name);
+    filename = FcConfigGetFilename (config, name);
     if (!filename)
+    {
+	FcStrBufString (&reason, (FcChar8 *)"No such file: ");
+	FcStrBufString (&reason, name ? name : (FcChar8 *)"(null)");
 	goto bail0;
+    }
     realfilename = FcConfigRealFilename (config, name);
     if (!realfilename)
+    {
+	FcStrBufString (&reason, (FcChar8 *)"No such realfile: ");
+	FcStrBufString (&reason, name ? name : (FcChar8 *)"(null)");
 	goto bail0;
+    }
     if (FcStrSetMember (config->availConfigFiles, realfilename))
     {
         FcStrFree (filename);
@@ -3582,7 +3592,11 @@ _FcConfigParse (FcConfig	*config,
 
     fd = FcOpen ((char *) realfilename, O_RDONLY);
     if (fd == -1)
+    {
+	FcStrBufString (&reason, (FcChar8 *)"Unable to open ");
+	FcStrBufString (&reason, realfilename);
 	goto bail1;
+    }
 
     do {
 	len = read (fd, buf, BUFSIZ);
@@ -3623,11 +3637,13 @@ bail0:
     if (!ret && complain_again)
     {
 	if (name)
-	    FcConfigMessage (0, FcSevereError, "Cannot %s config file \"%s\"", load ? "load" : "scan", name);
+	    FcConfigMessage (0, FcSevereError, "Cannot %s config file \"%s\": %s", load ? "load" : "scan", name, FcStrBufDoneStatic (&reason));
 	else
-	    FcConfigMessage (0, FcSevereError, "Cannot %s default config file", load ? "load" : "scan");
+	    FcConfigMessage (0, FcSevereError, "Cannot %s default config file: %s", load ? "load" : "scan", FcStrBufDoneStatic (&reason));
+	FcStrBufDestroy (&reason);
 	return FcFalse;
     }
+    FcStrBufDestroy (&reason);
     return ret;
 }