Port input method and text input from rootston

This ports swaywm/wlroots#1203, swaywm/wlroots#1303,
swaywm/wlroots#1308, swaywm/wlroots#1759 rootston part to sway.

include/sway/input/seat.h

@@ -5,6 +5,7 @@
 #include <wlr/types/wlr_seat.h>
 #include <wlr/util/edges.h>
 #include "sway/input/input-manager.h"
+#include "sway/input/text_input.h"
 
 struct sway_seat;
 
@@ -82,6 +83,8 @@ struct sway_seat {
 
 	list_t *deferred_bindings; // struct sway_binding
 
+	struct sway_input_method_relay im_relay;
+
 	struct wl_listener focus_destroy;
 	struct wl_listener new_node;
 	struct wl_listener request_start_drag;

include/sway/input/text_input.h

@@ -0,0 +1,63 @@
+#ifndef _SWAY_INPUT_TEXT_INPUT_H
+#define _SWAY_INPUT_TEXT_INPUT_H
+
+#include <wlr/types/wlr_text_input_v3.h>
+#include <wlr/types/wlr_input_method_v2.h>
+#include <wlr/types/wlr_surface.h>
+#include "sway/input/seat.h"
+
+/**
+ * The relay structure manages the relationship between text-input and
+ * input_method interfaces on a given seat. Multiple text-input interfaces may
+ * be bound to a relay, but at most one will be focused (reveiving events) at
+ * a time. At most one input-method interface may be bound to the seat. The
+ * relay manages life cycle of both sides. When both sides are present and
+ * focused, the relay passes messages between them.
+ *
+ * Text input focus is a subset of keyboard focus - if the text-input is
+ * in the focused state, wl_keyboard sent an enter as well. However, having
+ * wl_keyboard focused doesn't mean that text-input will be focused.
+ */
+struct sway_input_method_relay {
+	struct sway_seat *seat;
+
+	struct wl_list text_inputs; // sway_text_input::link
+	struct wlr_input_method_v2 *input_method; // doesn't have to be present
+
+	struct wl_listener text_input_new;
+	struct wl_listener text_input_enable;
+	struct wl_listener text_input_commit;
+	struct wl_listener text_input_disable;
+	struct wl_listener text_input_destroy;
+
+	struct wl_listener input_method_new;
+	struct wl_listener input_method_commit;
+	struct wl_listener input_method_destroy;
+};
+
+struct sway_text_input {
+	struct sway_input_method_relay *relay;
+
+	struct wlr_text_input_v3 *input;
+	// The surface getting seat's focus. Stored for when text-input cannot
+	// be sent an enter event immediately after getting focus, e.g. when
+	// there's no input method available. Cleared once text-input is entered.
+	struct wlr_surface *pending_focused_surface;
+
+	struct wl_list link;
+
+	struct wl_listener pending_focused_surface_destroy;
+};
+
+void sway_input_method_relay_init(struct sway_seat *seat,
+	struct sway_input_method_relay *relay);
+
+// Updates currently focused surface. Surface must belong to the same seat.
+void sway_input_method_relay_set_focus(struct sway_input_method_relay *relay,
+	struct wlr_surface *surface);
+
+struct sway_text_input *sway_text_input_create(
+	struct sway_input_method_relay *relay,
+	struct wlr_text_input_v3 *text_input);
+
+#endif

include/sway/server.h

@@ -7,11 +7,13 @@
 #include <wlr/render/wlr_renderer.h>
 #include <wlr/types/wlr_compositor.h>
 #include <wlr/types/wlr_data_device.h>
+#include <wlr/types/wlr_input_method_v2.h>
 #include <wlr/types/wlr_layer_shell_v1.h>
 #include <wlr/types/wlr_output_management_v1.h>
 #include <wlr/types/wlr_presentation_time.h>
 #include <wlr/types/wlr_relative_pointer_v1.h>
 #include <wlr/types/wlr_server_decoration.h>
+#include <wlr/types/wlr_text_input_v3.h>
 #include <wlr/types/wlr_xdg_shell.h>
 #include "config.h"
 #include "list.h"
@@ -71,6 +73,9 @@ struct sway_server {
 	struct wl_listener output_manager_apply;
 	struct wl_listener output_manager_test;
 
+	struct wlr_input_method_manager_v2 *input_method;
+	struct wlr_text_input_manager_v3 *text_input;
+
 	size_t txn_timeout_ms;
 	list_t *transactions;
 	list_t *dirty_nodes;

sway/input/seat.c

@@ -151,6 +151,7 @@ static void seat_send_focus(struct sway_node *node, struct sway_seat *seat) {
 
 		seat_keyboard_notify_enter(seat, view->surface);
 		seat_tablet_pads_notify_enter(seat, view->surface);
+		sway_input_method_relay_set_focus(&seat->im_relay, view->surface);
 
 		struct wlr_pointer_constraint_v1 *constraint =
 			wlr_pointer_constraints_v1_constraint_for_surface(
@@ -520,6 +521,8 @@ struct sway_seat *seat_create(const char *seat_name) {
 
 	wl_list_init(&seat->devices);
 
+	sway_input_method_relay_init(seat, &seat->im_relay);
+
 	wl_list_insert(&server.input->seats, &seat->link);
 
 	seatop_begin_default(seat);
@@ -951,6 +954,7 @@ void seat_set_focus(struct sway_seat *seat, struct sway_node *node) {
 			view_close_popups(last_focus->sway_container->view);
 		}
 		seat_send_unfocus(last_focus, seat);
+		sway_input_method_relay_set_focus(&seat->im_relay, NULL);
 		seat->has_focus = false;
 		return;
 	}