From fb4eb36e78a9d9337fd3decf70a6c13774ba551a Mon Sep 17 00:00:00 2001
From: Martin Jones <martin.jones@nokia.com>
Date: Wed, 8 Sep 2010 14:16:04 +1000
Subject: SpringAnimation velocity animation stop logic was fragile. Rather
 than stopping the animation when the target was reached, calculate the
 duration it will take.  This eliminates the possibility of rounding errors
 causing the animation to stop at the wrong time.

Task-number: QTBUG-13044
Reviewed-by: Aaron Kennedy
---
 .../util/qdeclarativespringanimation.cpp           | 37 +++++++++++++++-------
 1 file changed, 26 insertions(+), 11 deletions(-)

diff --git a/src/declarative/util/qdeclarativespringanimation.cpp b/src/declarative/util/qdeclarativespringanimation.cpp
index fce4097..e0fc45d 100644
--- a/src/declarative/util/qdeclarativespringanimation.cpp
+++ b/src/declarative/util/qdeclarativespringanimation.cpp
@@ -62,10 +62,12 @@ public:
 
     struct SpringAnimation {
         SpringAnimation()
-            : currentValue(0), to(0), velocity(0){}
+            : currentValue(0), to(0), velocity(0), start(0), duration(0) {}
         qreal currentValue;
         qreal to;
         qreal velocity;
+        int start;
+        int duration;
     };
     QHash<QDeclarativeProperty, SpringAnimation> activeAnimations;
 
@@ -135,7 +137,6 @@ void QDeclarativeSpringAnimationPrivate::tick(int time)
 
 bool QDeclarativeSpringAnimationPrivate::animate(const QDeclarativeProperty &property, SpringAnimation &animation, int elapsed)
 {
-
     qreal srcVal = animation.to;
 
     bool stop = false;
@@ -192,18 +193,14 @@ bool QDeclarativeSpringAnimationPrivate::animate(const QDeclarativeProperty &pro
             animation.currentValue += moveBy;
             if (haveModulus)
                 animation.currentValue = fmod(animation.currentValue, modulus);
-            if (animation.currentValue > animation.to) {
-                animation.currentValue = animation.to;
-                stop = true;
-            }
         } else {
             animation.currentValue -= moveBy;
             if (haveModulus && animation.currentValue < 0.0)
                 animation.currentValue = fmod(animation.currentValue, modulus) + modulus;
-            if (animation.currentValue < animation.to) {
-                animation.currentValue = animation.to;
-                stop = true;
-            }
+        }
+        if (lastTime - animation.start >= animation.duration) {
+            animation.currentValue = animation.to;
+            stop = true;
         }
     }
 
@@ -222,8 +219,18 @@ void QDeclarativeSpringAnimationPrivate::updateMode()
         mode = Track;
     else if (spring > 0.)
         mode = Spring;
-    else
+    else {
         mode = Velocity;
+        QHash<QDeclarativeProperty, SpringAnimation>::iterator it;
+        for (it = activeAnimations.begin(); it != activeAnimations.end(); ++it) {
+            SpringAnimation &animation = *it;
+            animation.start = lastTime;
+            qreal dist = qAbs(animation.currentValue - animation.to);
+            if (haveModulus && dist > modulus / 2)
+                dist = modulus - fmod(dist, modulus);
+            animation.duration = dist / velocityms;
+        }
+    }
 }
 
 /*!
@@ -378,6 +385,7 @@ void QDeclarativeSpringAnimation::setModulus(qreal modulus)
     if (d->modulus != modulus) {
         d->haveModulus = modulus != 0.0;
         d->modulus = modulus;
+        d->updateMode();
         emit modulusChanged();
     }
 }
@@ -429,10 +437,17 @@ void QDeclarativeSpringAnimation::transition(QDeclarativeStateActions &actions,
             QDeclarativeSpringAnimationPrivate::SpringAnimation &animation
                     = d->activeAnimations[property];
             animation.to = d->actions->at(i).toValue.toReal();
+            animation.start = d->lastTime;
             if (d->fromIsDefined)
                 animation.currentValue = d->actions->at(i).fromValue.toReal();
             else
                 animation.currentValue = property.read().toReal();
+            if (d->mode == QDeclarativeSpringAnimationPrivate::Velocity) {
+                qreal dist = qAbs(animation.currentValue - animation.to);
+                if (d->haveModulus && dist > d->modulus / 2)
+                    dist = d->modulus - fmod(dist, d->modulus);
+                animation.duration = dist / d->velocityms;
+            }
         }
     }
 }
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