Implement key repeat for pressed key bindings

Each sway_keyboard is provided with a wayland timer event source.
When a valid keypress binding has been found, a callback to
handle_keyboard_repeat is set. Any key event will either clear
the callback or (if the new key event is a valid keypress binding)
delay the callback again.

include/sway/input/keyboard.h

@@ -38,6 +38,11 @@ struct sway_keyboard {
 	struct sway_shortcut_state state_keysyms_raw;
 	struct sway_shortcut_state state_keycodes;
 	struct sway_binding *held_binding;
+
+	struct wl_event_source *key_repeat_source;
+	struct sway_binding *repeat_binding;
+	int key_repeat_initial_delay; // first key repeat event delay, in ms
+	int key_repeat_step_delay; // subsequent repeat delay, in ms
 };
 
 struct sway_keyboard *sway_keyboard_create(struct sway_seat *seat,

sway/input/keyboard.c

@@ -264,6 +264,7 @@ static void handle_keyboard_key(struct wl_listener *listener, void *data) {
 	}
 
 	// Identify and execute active pressed binding
+	struct sway_binding *next_repeat_binding = NULL;
 	if (event->state == WLR_KEY_PRESSED) {
 		struct sway_binding *binding_pressed = NULL;
 		get_active_binding(&keyboard->state_keycodes,
@@ -279,6 +280,21 @@ static void handle_keyboard_key(struct wl_listener *listener, void *data) {
 		if (binding_pressed) {
 			seat_execute_command(seat, binding_pressed);
 			handled = true;
+			next_repeat_binding = binding_pressed;
+		}
+	}
+
+	// Set up (or clear) keyboard repeat for a pressed binding
+	if (next_repeat_binding) {
+		keyboard->repeat_binding = next_repeat_binding;
+		if (wl_event_source_timer_update(keyboard->key_repeat_source,
+				keyboard->key_repeat_initial_delay) < 0) {
+			wlr_log(WLR_DEBUG, "failed to set key repeat timer");
+		}
+	} else if (keyboard->repeat_binding) {
+		keyboard->repeat_binding = NULL;
+		if (wl_event_source_timer_update(keyboard->key_repeat_source, 0) < 0) {
+			wlr_log(WLR_DEBUG, "failed to disarm key repeat timer");
 		}
 	}
 
@@ -303,6 +319,22 @@ static void handle_keyboard_key(struct wl_listener *listener, void *data) {
 	transaction_commit_dirty();
 }
 
+static int handle_keyboard_repeat(void *data) {
+	struct sway_keyboard *keyboard = (struct sway_keyboard *)data;
+	if (keyboard->repeat_binding) {
+		// We queue the next event first, as the command might cancel it
+		if (wl_event_source_timer_update(keyboard->key_repeat_source,
+				keyboard->key_repeat_step_delay) < 0) {
+			wlr_log(WLR_DEBUG, "failed to update key repeat timer");
+		}
+
+		seat_execute_command(keyboard->seat_device->sway_seat,
+				keyboard->repeat_binding);
+		transaction_commit_dirty();
+	}
+	return 0;
+}
+
 static void handle_keyboard_modifiers(struct wl_listener *listener,
 		void *data) {
 	struct sway_keyboard *keyboard =
@@ -328,6 +360,11 @@ struct sway_keyboard *sway_keyboard_create(struct sway_seat *seat,
 	wl_list_init(&keyboard->keyboard_key.link);
 	wl_list_init(&keyboard->keyboard_modifiers.link);
 
+	keyboard->key_repeat_source = wl_event_loop_add_timer(server.wl_event_loop,
+			handle_keyboard_repeat, keyboard);
+	keyboard->key_repeat_initial_delay = 660;
+	keyboard->key_repeat_step_delay = 40;
+
 	return keyboard;
 }
 
@@ -441,5 +478,6 @@ void sway_keyboard_destroy(struct sway_keyboard *keyboard) {
 	}
 	wl_list_remove(&keyboard->keyboard_key.link);
 	wl_list_remove(&keyboard->keyboard_modifiers.link);
+	wl_event_source_remove(keyboard->key_repeat_source);
 	free(keyboard);
 }