compositor: Make spring model always use the same time step

compositor/compositor.c

@@ -163,16 +163,16 @@ wlsc_spring_update(struct wlsc_spring *spring, uint32_t msec)
 {
 	double force, v, current, step;
 
-	step = (msec - spring->timestamp) / 300.0;
-	spring->timestamp = msec;
-
+	step = 0.01;
+	while (4 < msec - spring->timestamp) {
 		current = spring->current;
 		v = current - spring->previous;
 		force = spring->k * (spring->target - current) / 10.0 +
 			(spring->previous - current) - v * spring->friction;
 
 		spring->current =
-		current + (current - spring->previous) + force * step * step;
+			current + (current - spring->previous) +
+			force * step * step;
 		spring->previous = current;
 
 #if 0
@@ -191,6 +191,8 @@ wlsc_spring_update(struct wlsc_spring *spring, uint32_t msec)
 			spring->previous = 0.0;
 		}
 #endif
+		spring->timestamp += 4;
+	}
 }
 
 WL_EXPORT int
@@ -2070,7 +2072,7 @@ wlsc_compositor_init(struct wlsc_compositor *ec, struct wl_display *display)
 	wl_list_init(&ec->output_list);
 	wl_list_init(&ec->binding_list);
 	wl_list_init(&ec->animation_list);
-	wlsc_spring_init(&ec->fade.spring, 0.8, 0.0, 0.0);
+	wlsc_spring_init(&ec->fade.spring, 40.0, 1.0, 1.0);
 	ec->fade.animation.frame = fade_frame;
 	wl_list_init(&ec->fade.animation.link);
 

compositor/meego-tablet-shell.c

@@ -684,6 +684,5 @@ shell_init(struct wlsc_compositor *compositor)
 		meego_tablet_shell_set_selection_focus;
 	launch_ux_daemon(shell);
 
-	wlsc_spring_init(&compositor->fade.spring, 40.0, 1.0, 1.0);
 	meego_tablet_shell_set_state(shell, STATE_STARTING);
 }