--- SIDPlayer/src/prefs.cpp	2001/01/04 19:54:13	1.2
+++ SIDPlayer/src/prefs.cpp	2001/01/16 16:53:26	1.3
@@ -61,10 +61,21 @@ void PrefsInit(int argc, char **argv)
 		if (strlen(*argv) < 3 || argv[0][0] != '-' || argv[0][1] != '-')
 			continue;
 		const char *keyword = *argv + 2;
+
+		// Find descriptor for keyword
 		const prefs_desc *d = find_prefs_desc(keyword);
+		bool negated_bool = false;
 		if (d == NULL) {
-			printf("WARNING: Unrecognized argument '%s'\n", *argv);
-			continue;
+			// We also accept boolean arguments in the form '--nokeyword'
+			if (strncmp(keyword, "no", 2) == 0) {
+				negated_bool = true;
+				keyword += 2;
+				d = find_prefs_desc(keyword);
+			}
+			if (d == NULL) {
+				printf("WARNING: Unrecognized argument '%s'\n", *argv);
+				continue;
+			}
 		}
 
 		// Add/replace prefs item
@@ -81,13 +92,24 @@ void PrefsInit(int argc, char **argv)
 					PrefsReplaceString(keyword, *argv);
 				break;
 
-			case TYPE_BOOLEAN:
-				if (argc > 1 && argv[1][0] != '-') {
-					argc--; argv++;
-					PrefsReplaceBool(keyword, !strcmp(*argv, "true") || !strcmp(*argv, "on"));
+			case TYPE_BOOLEAN: {
+				bool new_value;
+				if (negated_bool)
+					new_value = false;
+				else if (argc > 1 && argv[1][0] != '-') {
+					if (!strcmp(argv[1], "true") || !strcmp(argv[1], "on") || !strcmp(argv[1], "yes")) {
+						new_value = true;
+						argc--; argv++;
+					} else if (!strcmp(argv[1], "false") || !strcmp(argv[1], "off") || !strcmp(argv[1], "no")) {
+						new_value = false;
+						argc--; argv++;
+					} else
+						new_value = true;
 				} else
-					PrefsReplaceBool(keyword, true);
+					new_value = true;
+				PrefsReplaceBool(keyword, new_value);
 				break;
+			}
 
 			case TYPE_INT32:
 				if (argc < 2) {
@@ -124,12 +146,60 @@ void PrefsExit(void)
 
 
 /*
+ *  Print preferences options help
+ */
+
+static void print_options(const prefs_desc *list)
+{
+	while (list->type != TYPE_END) {
+		if (list->help) {
+			const char *typestr, *defstr;
+			char numstr[32];
+			switch (list->type) {
+				case TYPE_STRING:
+					typestr = "STRING";
+					defstr = PrefsFindString(list->name);
+					if (defstr == NULL)
+						defstr = "none";
+					break;
+				case TYPE_BOOLEAN:
+					typestr = "BOOL";
+					if (PrefsFindBool(list->name))
+						defstr = "true";
+					else
+						defstr = "false";
+					break;
+				case TYPE_INT32:
+					typestr = "NUMBER";
+					sprintf(numstr, "%d", PrefsFindInt32(list->name));
+					defstr = numstr;
+					break;
+				default:
+					typestr = "<unknown>";
+					defstr = "none";
+					break;
+			}
+			printf("  --%s %s\n    %s [default=%s]\n", list->name, typestr, list->help, defstr);
+		}
+		list++;
+	}
+}
+
+void PrefsPrintUsage(void)
+{
+	printf("\nGeneral options:\n");
+	print_options(common_prefs_items);
+	printf("\nBoolean options can be specified as '--OPTION true|on|yes' and\n'--OPTION false|off|no', or as '--OPTION' and '--noOPTION'.\n");
+}
+
+
+/*
  *  Find preferences descriptor by keyword
  */
 
 static prefs_desc *find_prefs_desc(const char *name, prefs_desc *list)
 {
-	while (list->type != TYPE_ANY) {
+	while (list->type != TYPE_END) {
 		if (strcmp(list->name, name) == 0)
 			return list;
 		list++;