Allow switching the user from the command line

This is a feature that many people have asked for. This implementation is
somewhat simplistic because we simply use a different name for the
program settings - but interestingly enough this appears to be enough to
capture a lot of the core functionality that people are looking for in
multi-user support.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

core/qt-init.cpp

@@ -4,6 +4,8 @@
 #include <QTextCodec>
 #include "helpers.h"
 
+char *settings_suffix = NULL;
+
 void init_qt_late()
 {
 	QApplication *application = qApp;
@@ -19,7 +21,14 @@ void init_qt_late()
 
 	QCoreApplication::setOrganizationName("Subsurface");
 	QCoreApplication::setOrganizationDomain("subsurface.hohndel.org");
-	QCoreApplication::setApplicationName("Subsurface");
+	// enable user specific settings (based on command line argument)
+	if (settings_suffix) {
+		if (verbose)
+			qDebug() << "using custom config for" << QString("Subsurface-%1").arg(settings_suffix);
+		QCoreApplication::setApplicationName(QString("Subsurface-%1").arg(settings_suffix));
+	} else {
+		QCoreApplication::setApplicationName("Subsurface");
+	}
 	// find plugins installed in the application directory (without this SVGs don't work on Windows)
 	QCoreApplication::addLibraryPath(QCoreApplication::applicationDirPath());
 	QLocale loc;

core/subsurfacestartup.c

@@ -197,6 +197,11 @@ void parse_argument(const char *arg)
 			continue;
 		case '-':
 			/* long options with -- */
+			/* first test for --user=bla which allows the use of user specific settings */
+			if (strncmp(arg, "--user=", sizeof("--user=") - 1) == 0) {
+				settings_suffix = strdup(arg + sizeof("--user=") - 1);
+				return;
+			}
 			if (strcmp(arg, "--help") == 0) {
 				print_help();
 				exit(0);
@@ -254,8 +259,10 @@ void setup_system_prefs(void)
 	subsurface_OS_pref_setup();
 	default_prefs.divelist_font = strdup(system_divelist_default_font);
 	default_prefs.font_size = system_divelist_default_font_size;
-	default_prefs.default_filename = system_default_filename();
 
+#if !defined(SUBSURFACE_MOBILE)
+	default_prefs.default_filename = system_default_filename();
+#endif
 	env = getenv("LC_MEASUREMENT");
 	if (!env)
 		env = getenv("LC_ALL");

core/subsurfacestartup.h

@@ -19,6 +19,8 @@ void free_prefs(void);
 void copy_prefs(struct preferences *src, struct preferences *dest);
 void print_files(void);
 
+extern char *settings_suffix;
+
 #ifdef __cplusplus
 }
 #endif