Shim client.background and client.placeholder

These are not supported by sway, but are valid i3 commands and should not
cause config errors.

Also includes a couple of minor touch-ups.

include/sway/commands.h

@@ -103,6 +103,7 @@ sway_cmd cmd_bar;
 sway_cmd cmd_bindcode;
 sway_cmd cmd_bindsym;
 sway_cmd cmd_border;
+sway_cmd cmd_client_noop;
 sway_cmd cmd_client_focused;
 sway_cmd cmd_client_focused_inactive;
 sway_cmd cmd_client_unfocused;

sway/commands.c

@@ -77,8 +77,10 @@ static struct cmd_handler handlers[] = {
 	{ "bar", cmd_bar },
 	{ "bindcode", cmd_bindcode },
 	{ "bindsym", cmd_bindsym },
+	{ "client.background", cmd_client_noop },
 	{ "client.focused", cmd_client_focused },
 	{ "client.focused_inactive", cmd_client_focused_inactive },
+	{ "client.placeholder", cmd_client_noop },
 	{ "client.unfocused", cmd_client_unfocused },
 	{ "client.urgent", cmd_client_urgent },
 	{ "default_border", cmd_default_border },

sway/commands/client.c

@@ -64,27 +64,27 @@ static struct cmd_results *handle_command(int argc, char **argv,
 
 	if (!parse_color_float(argv[0], class->border)) {
 		return cmd_results_new(CMD_INVALID, cmd_name,
-				"Unable to parse border color");
+				"Unable to parse border color '%s'", argv[0]);
 	}
 
 	if (!parse_color_float(argv[1], class->background)) {
 		return cmd_results_new(CMD_INVALID, cmd_name,
-				"Unable to parse background color");
+				"Unable to parse background color '%s'", argv[1]);
 	}
 
 	if (!parse_color_float(argv[2], class->text)) {
 		return cmd_results_new(CMD_INVALID, cmd_name,
-				"Unable to parse text color");
+				"Unable to parse text color '%s'", argv[2]);
 	}
 
 	if (!parse_color_float(argv[3], class->indicator)) {
 		return cmd_results_new(CMD_INVALID, cmd_name,
-				"Unable to parse indicator color");
+				"Unable to parse indicator color '%s'", argv[3]);
 	}
 
 	if (!parse_color_float(argv[4], class->child_border)) {
 		return cmd_results_new(CMD_INVALID, cmd_name,
-				"Unable to parse child border color");
+				"Unable to parse child border color '%s'", argv[4]);
 	}
 
 	if (config->active) {
@@ -114,3 +114,8 @@ struct cmd_results *cmd_client_unfocused(int argc, char **argv) {
 struct cmd_results *cmd_client_urgent(int argc, char **argv) {
 	return handle_command(argc, argv, &config->border_colors.urgent, "client.urgent");
 }
+
+struct cmd_results *cmd_client_noop(int argc, char **argv) {
+	wlr_log(WLR_INFO, "Warning: %s is ignored by sway", argv[-1]);
+	return cmd_results_new(CMD_SUCCESS, NULL, NULL);
+}