POSIX: Move default config file location to '$XDG_CONFIG_HOME/scummvm/scummvm.ini'.

This is what the XDG Base Directory Specification suggests to use. We still
use the old location of '~/.scummvmrc' in case that is present.

This tackles an aspect of bug #6036 "POSIX: Use XDG dirs instead of HOME".

README

@@ -2329,7 +2329,15 @@ By default, the configuration file is saved in, and loaded from:
     previous default location of '<windir>\scummvm.ini' will be kept.
 
     Unix:
-    ~/.scummvmrc
+    We follow the XDG Base Directory Specification. This means our
+    configuration can be found in:
+    $XDG_CONFIG_HOME/scummvm/scummvm.ini
+
+    If XDG_CONFIG_HOME is not defined or empty, '~/.config' will be used
+    as value for XDG_CONFIG_HOME in accordance with the specification.
+
+    If an earlier version of ScummVM was installed on your system, the
+    previous default location of '~/.scummvmrc' will be kept.
 
     Mac OS X:
     ~/Library/Preferences/ScummVM Preferences

backends/platform/sdl/posix/posix.cpp

@@ -150,11 +150,54 @@ bool OSystem_POSIX::hasFeature(Feature f) {
 Common::String OSystem_POSIX::getDefaultConfigFileName() {
 	Common::String configFile;
 
-	// On POSIX type systems, by default we store the config file inside
-	// to the HOME directory of the user.
-	const char *home = getenv("HOME");
-	if (home != NULL && (strlen(home) + 1 + _baseConfigName.size()) < MAXPATHLEN) {
-		configFile = Common::String::format("%s/%s", home, _baseConfigName.c_str());
+	Common::String prefix;
+#ifdef MACOSX
+	prefix = getenv("HOME");
+#elif !defined(SAMSUNGTV)
+	const char *envVar;
+	// Our old configuration file path for POSIX systems was ~/.scummvmrc.
+	// If that file exists, we still use it.
+	envVar = getenv("HOME");
+	if (envVar && *envVar) {
+		configFile = envVar;
+		configFile += '/';
+		configFile += ".scummvmrc";
+
+		if (configFile.size() < MAXPATHLEN) {
+			struct stat sb;
+			if (stat(configFile.c_str(), &sb) == 0) {
+				return configFile;
+			}
+		}
+	}
+
+	// On POSIX systems we follow the XDG Base Directory Specification for
+	// where to store files. The version we based our code upon can be found
+	// over here: http://standards.freedesktop.org/basedir-spec/basedir-spec-0.8.html
+	envVar = getenv("XDG_CONFIG_HOME");
+	if (!envVar || !*envVar) {
+		envVar = getenv("HOME");
+		if (!envVar) {
+			return 0;
+		}
+
+		if (assureDirectoryExists(".config", envVar)) {
+			prefix = envVar;
+			prefix += "/.config";
+		}
+	} else {
+		prefix = envVar;
+	}
+
+	if (!prefix.empty() && assureDirectoryExists("scummvm", prefix.c_str())) {
+		prefix += "/scummvm";
+	}
+#endif
+
+	if (!prefix.empty() && (prefix.size() + 1 + _baseConfigName.size()) < MAXPATHLEN) {
+		configFile = prefix;
+		configFile += '/';
+		configFile += _baseConfigName;
 	} else {
 		configFile = _baseConfigName;
 	}

backends/platform/sdl/posix/posix.h

@@ -28,7 +28,7 @@
 class OSystem_POSIX : public OSystem_SDL {
 public:
 	// Let the subclasses be able to change _baseConfigName in the constructor
-	OSystem_POSIX(Common::String baseConfigName = ".scummvmrc");
+	OSystem_POSIX(Common::String baseConfigName = "scummvm.ini");
 	virtual ~OSystem_POSIX() {}
 
 	virtual bool hasFeature(Feature f);