compositor-wayland: Synchronise keyboard state with parent

Use the wl_keyboard::modifiers events our parent helpfully sends us to
make sure our views of the keyboard state are always identical, rather
than relying on key press events to do the right thing.

Signed-off-by: Daniel Stone <daniel@fooishbar.org>

src/compositor-wayland.c

@@ -92,6 +92,7 @@ struct wayland_input {
 	struct wl_keyboard *keyboard;
 	struct wl_touch *touch;
 	struct wl_list link;
+	uint32_t key_serial;
 };
 
 
@@ -533,6 +534,8 @@ input_handle_pointer_enter(void *data, struct wl_pointer *pointer,
 	struct wayland_output *output;
 	struct wayland_compositor *c = input->compositor;
 
+	/* XXX: If we get a modifier event immediately before the focus,
+	 *      we should try to keep the same serial. */
 	output = wl_surface_get_user_data(surface);
 	notify_pointer_focus(&c->base.seat->seat, &output->base, x, y);
 	wl_pointer_set_cursor(input->pointer, serial, NULL, 0, 0);
@@ -640,7 +643,8 @@ input_handle_keyboard_enter(void *data,
 	struct wayland_input *input = data;
 	struct wayland_compositor *c = input->compositor;
 
-	/* XXX: Need to wait for modifier event and send with state then. */
+	/* XXX: If we get a modifier event immediately before the focus,
+	 *      we should try to keep the same serial. */
 	notify_keyboard_focus_in(&c->base.seat->seat, keys,
 				 STATE_UPDATE_AUTOMATIC);
 }
@@ -664,19 +668,35 @@ input_handle_key(void *data, struct wl_keyboard *keyboard,
 	struct wayland_input *input = data;
 	struct wayland_compositor *c = input->compositor;
 
+	input->key_serial = serial;
 	notify_key(&c->base.seat->seat, time, key,
 		   state ? WL_KEYBOARD_KEY_STATE_PRESSED :
 			   WL_KEYBOARD_KEY_STATE_RELEASED,
-		   STATE_UPDATE_AUTOMATIC);
+		   STATE_UPDATE_NONE);
 }
 
 static void
 input_handle_modifiers(void *data, struct wl_keyboard *keyboard,
-		       uint32_t serial, uint32_t mods_depressed,
+		       uint32_t serial_in, uint32_t mods_depressed,
 		       uint32_t mods_latched, uint32_t mods_locked,
 		       uint32_t group)
 {
-	/* XXX notify_modifiers(); */
+	struct wayland_input *input = data;
+	struct wayland_compositor *c = input->compositor;
+	uint32_t serial_out;
+
+	/* If we get a key event followed by a modifier event with the
+	 * same serial number, then we try to preserve those semantics by
+	 * reusing the same serial number on the way out too. */
+	if (serial_in == input->key_serial)
+		serial_out = wl_display_get_serial(c->base.wl_display);
+	else
+		serial_out = wl_display_next_serial(c->base.wl_display);
+
+	xkb_state_update_mask(c->base.seat->xkb_state.state,
+			      mods_depressed, mods_latched,
+			      mods_locked, 0, 0, group);
+	notify_modifiers(&c->base.seat->seat, serial_out);
 }
 
 static const struct wl_keyboard_listener keyboard_listener = {