From 3ff589df782b4465124c860717ea81f020e8d782 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kristian=20H=C3=B8gsberg?= <krh@bitplanet.net>
Date: Sat, 29 Oct 2011 13:41:18 -0400
Subject: [PATCH] compositor: Make spring model always use the same time step

---
 compositor/compositor.c         | 44 +++++++++++++++++----------------
 compositor/meego-tablet-shell.c |  1 -
 2 files changed, 23 insertions(+), 22 deletions(-)

diff --git a/compositor/compositor.c b/compositor/compositor.c
index 064735b0..dd932fe6 100644
--- a/compositor/compositor.c
+++ b/compositor/compositor.c
@@ -163,34 +163,36 @@ 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;
 
-	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;
-	spring->previous = current;
+		spring->current =
+			current + (current - spring->previous) +
+			force * step * step;
+		spring->previous = current;
 
 #if 0
-	if (spring->current >= 1.0) {
+		if (spring->current >= 1.0) {
 #ifdef TWEENER_BOUNCE
-		spring->current = 2.0 - spring->current;
-		spring->previous = 2.0 - spring->previous;
+			spring->current = 2.0 - spring->current;
+			spring->previous = 2.0 - spring->previous;
 #else
-		spring->current = 1.0;
-		spring->previous = 1.0;
+			spring->current = 1.0;
+			spring->previous = 1.0;
 #endif
-	}
+		}
 
-	if (spring->current <= 0.0) {
-		spring->current = 0.0;
-		spring->previous = 0.0;
-	}
+		if (spring->current <= 0.0) {
+			spring->current = 0.0;
+			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);
 
diff --git a/compositor/meego-tablet-shell.c b/compositor/meego-tablet-shell.c
index 450888b2..35b97758 100644
--- a/compositor/meego-tablet-shell.c
+++ b/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);
 }