shell: Use its own timer for the screensaver timeout

Previously, the shell would change the idle_time of the compositor to
the screensaver timeout and wake the compositor again, so that after
the timeout the compositor would fade to black and then the shell would
receive the lock signal again and would set the dpms state of the
outputs to off.

Instead, use a screensaver-specific timer for that, and call lock
without the back and forth between the shell and core Weston.

src/shell.c

@@ -135,6 +135,7 @@ struct desktop_shell {
 		int duration;
 		struct wl_resource *binding;
 		struct weston_process process;
+		struct wl_event_source *timer;
 	} screensaver;
 
 	struct {
@@ -384,7 +385,7 @@ shell_configuration(struct desktop_shell *shell, const char *config_file)
 	parse_config_file(config_file, cs, ARRAY_LENGTH(cs), shell);
 
 	shell->screensaver.path = path;
-	shell->screensaver.duration = duration;
+	shell->screensaver.duration = duration * 1000;
 	shell->binding_modifier = get_modifier(modifier);
 	shell->win_animation_type = get_animation_type(win_animation);
 	shell->workspaces.num = num_workspaces > 0 ? num_workspaces : 1;
@@ -2135,6 +2136,19 @@ static const struct wl_shell_interface shell_implementation = {
 	shell_get_shell_surface
 };
 
+static void
+shell_fade(struct desktop_shell *shell, enum fade_type type);
+
+static int
+screensaver_timeout(void *data)
+{
+	struct desktop_shell *shell = data;
+
+	shell_fade(shell, FADE_OUT);
+
+	return 1;
+}
+
 static void
 handle_screensaver_sigchld(struct weston_process *proc, int status)
 {
@@ -2339,7 +2353,6 @@ resume_desktop(struct desktop_shell *shell)
 	restore_focus_state(shell, get_current_workspace(shell));
 
 	shell->locked = false;
-	shell->compositor->idle_time = shell->compositor->option_idle_time;
 	weston_compositor_wake(shell->compositor);
 	weston_compositor_damage_all(shell->compositor);
 }
@@ -3306,9 +3319,9 @@ screensaver_configure(struct weston_surface *surface, int32_t sx, int32_t sy)
 		wl_list_insert(shell->lock_layer.surface_list.prev,
 			       &surface->layer_link);
 		weston_surface_update_transform(surface);
-		shell->compositor->idle_time = shell->screensaver.duration;
+		wl_event_source_timer_update(shell->screensaver.timer,
+					     shell->screensaver.duration);
 		shell_fade(shell, FADE_IN);
-		weston_compositor_wake(shell->compositor);
 		shell->compositor->state = WESTON_COMPOSITOR_IDLE;
 	}
 }
@@ -4135,6 +4148,9 @@ module_init(struct weston_compositor *ec,
 	loop = wl_display_get_event_loop(ec->wl_display);
 	wl_event_loop_add_idle(loop, launch_desktop_shell_process, shell);
 
+	shell->screensaver.timer =
+		wl_event_loop_add_timer(loop, screensaver_timeout, shell);
+
 	wl_list_for_each(seat, &ec->seat_list, link)
 		create_pointer_focus_listener(seat);