Add a new xkb_switch_layout command

This allows users to programatically change the active layout.

include/sway/commands.h

@@ -260,6 +260,7 @@ sway_cmd input_cmd_xkb_model;
 sway_cmd input_cmd_xkb_numlock;
 sway_cmd input_cmd_xkb_options;
 sway_cmd input_cmd_xkb_rules;
+sway_cmd input_cmd_xkb_switch_layout;
 sway_cmd input_cmd_xkb_variant;
 
 sway_cmd output_cmd_background;

sway/commands/input.c

@@ -31,6 +31,7 @@ static struct cmd_handler input_handlers[] = {
 	{ "xkb_model", input_cmd_xkb_model },
 	{ "xkb_options", input_cmd_xkb_options },
 	{ "xkb_rules", input_cmd_xkb_rules },
+	{ "xkb_switch_layout", input_cmd_xkb_switch_layout },
 	{ "xkb_variant", input_cmd_xkb_variant },
 };
 
@@ -86,7 +87,8 @@ struct cmd_results *cmd_input(int argc, char **argv) {
 			input_handlers, sizeof(input_handlers));
 	}
 
-	if (!res || res->status == CMD_SUCCESS) {
+	if ((!res || res->status == CMD_SUCCESS) &&
+			strcmp(argv[1], "xkb_switch_layout") != 0) {
 		char *error = NULL;
 		struct input_config *ic =
 			store_input_config(config->handler_context.input_config, &error);

sway/commands/input/xkb_switch_layout.c

@@ -0,0 +1,51 @@
+#define _POSIX_C_SOURCE 200809L
+#include "sway/config.h"
+#include "sway/commands.h"
+#include "sway/input/input-manager.h"
+#include "log.h"
+
+static void switch_layout(struct wlr_keyboard *kbd, xkb_layout_index_t idx) {
+	xkb_layout_index_t num_layouts = xkb_keymap_num_layouts(kbd->keymap);
+	if (idx >= num_layouts) {
+		return;
+	}
+	wlr_keyboard_notify_modifiers(kbd, kbd->modifiers.depressed,
+		kbd->modifiers.latched, kbd->modifiers.locked, idx);
+}
+
+struct cmd_results *input_cmd_xkb_switch_layout(int argc, char **argv) {
+	struct cmd_results *error = NULL;
+	if ((error = checkarg(argc, "xkb_switch_layout", EXPECTED_EQUAL_TO, 1))) {
+		return error;
+	}
+	struct input_config *ic = config->handler_context.input_config;
+	if (!ic) {
+		return cmd_results_new(CMD_FAILURE, "No input device defined.");
+	}
+
+	if (config->reading || !config->active) {
+		return cmd_results_new(CMD_DEFER, NULL);
+	}
+
+	const char *layout_str = argv[0];
+
+	char *end;
+	int layout = strtol(layout_str, &end, 10);
+	if (layout_str[0] == '\0' || end[0] != '\0' || layout < 0) {
+		return cmd_results_new(CMD_FAILURE, "Invalid layout index.");
+	}
+
+	struct sway_input_device *dev;
+	wl_list_for_each(dev, &server.input->devices, link) {
+		if (strcmp(ic->identifier, "*") != 0 &&
+				strcmp(ic->identifier, dev->identifier) != 0) {
+			continue;
+		}
+		if (dev->wlr_device->type != WLR_INPUT_DEVICE_KEYBOARD) {
+			continue;
+		}
+		switch_layout(dev->wlr_device->keyboard, layout);
+	}
+
+	return cmd_results_new(CMD_SUCCESS, NULL);
+}

sway/meson.build

@@ -164,6 +164,7 @@ sway_sources = files(
 	'commands/input/xkb_numlock.c',
 	'commands/input/xkb_options.c',
 	'commands/input/xkb_rules.c',
+	'commands/input/xkb_switch_layout.c',
 	'commands/input/xkb_variant.c',
 
 	'commands/output/background.c',