Fix scrollTo

1 files changed, 38 insertions, 21 deletions

diff --git a/qkineticscroller.cpp b/qkineticscroller.cpp
index bdf4cfa..47d3aed 100644
--- a/qkineticscroller.cpp
+++ b/qkineticscroller.cpp
@@ -860,6 +860,9 @@ void QKineticScroller::scrollTo(const QPointF &pos, int scrollTime)
 {
     Q_D(QKineticScroller);
 
+    if (scrollTime <= 0)
+        scrollTime = 1;
+
     qreal time = qreal(scrollTime) / 1000;
 
     if ((pos == contentPosition()) ||
@@ -887,18 +890,25 @@ void QKineticScroller::scrollTo(const QPointF &pos, int scrollTime)
 
     // v(t) = vstart * exponentialDecelerationBase ^ t - linearDecelerationFactor * t
     // pos(t) = integrate(v(t) * dt)
-    // pos(t) = vstart * eDB ^ t / ln(eDB) -  lDF / 2 * t ^ 2
+    // pos(t) = vstart * (eDB ^ t / ln(eDB) + C) -  lDF / 2 * t ^ 2
     //
-    // pos(scrollTime) = pos - contentsPos()
-    // vstart = ((lDF / 2) * scrollTime ^ 2 + (pos - contentPos())) * ln(eDB) / eDB ^ scrollTime
+    // pos(time) = pos - contentsPos()
+    // vstart = ((lDF / 2) * time ^ 2 + (pos - contentPos())) / (eDB ^ time / ln(eDB) + C)
+    // (for C = -1/ln(eDB) )
+
+    QPointF scrollDir(qSign(pos.x()-contentPosition().x()),
+                      qSign(pos.y()-contentPosition().y()));
 
-    QPointF v = (QPointF(1, 1) * (d->linearDecelerationFactor / qreal(2)) * qreal(time) * qreal(time) + (pos - contentPosition()) / d->pixelPerMeter);
+    QPointF v = (scrollDir * (d->linearDecelerationFactor / qreal(2)) * qreal(time) * qreal(time) + (pos - contentPosition()) / d->pixelPerMeter);
     if (d->exponentialDecelerationBase != qreal(1))
-     v *= qLn(d->exponentialDecelerationBase) / qPow(d->exponentialDecelerationBase, time);
+        v /= (qPow(d->exponentialDecelerationBase, time) - 1) / qLn(d->exponentialDecelerationBase);
+    else
+        v /= time;
 
-    qKSDebug() << "QAbstractKineticScroller::scrollTo(" << pos << ", " << v;
-    qKSDebug() << "QAbstr " << d->linearDecelerationFactor <<" 1: "<< (qreal(2) * qreal(scrollTime) * qreal(scrollTime)) << " 2: " << (pos - contentPosition()) << " 3: " <<
-                qLn(d->exponentialDecelerationBase) << "4: " << qPow(d->exponentialDecelerationBase, scrollTime);
+    qKSDebug() << "QAbstractKineticScroller::scrollTo pos:" << pos << "v:" << v <<"minV:"<<vMin;
+    qKSDebug() << "QAbstr " << d->linearDecelerationFactor <<" 1: "<< (qreal(2) * qreal(time) * qreal(scrollTime)) << " 2: " << (pos - contentPosition()) << " 3: " <<
+                qLn(d->exponentialDecelerationBase) << "4: " << qPow(d->exponentialDecelerationBase, time)
+                << " 5: "<<((qPow(d->exponentialDecelerationBase, time) - 1) / qLn(d->exponentialDecelerationBase));
 
 
     // start the scrolling
@@ -990,6 +1000,12 @@ void QKineticScrollerPrivate::setContentPositionHelper(const QPointF &deltaPos)
     qreal newOvershootX = (maxPos.x() || alwaysOvershoot) ? newPos.x() - newClampedPos.x() : 0;
     qreal newOvershootY = (maxPos.y() || alwaysOvershoot) ? newPos.y() - newClampedPos.y() : 0;
 
+    // --- sanity check for scrollTo in case we can't even scroll that direction
+    if (!(maxPos.x() || alwaysOvershoot))
+        scrollToX = false;
+    if (!(maxPos.y() || alwaysOvershoot))
+        scrollToY = false;
+
     QPointF oldScrollToDist = scrollToPosition - oldPos;
     QPointF newScrollToDist = scrollToPosition - newPos;
 
@@ -997,7 +1013,12 @@ void QKineticScrollerPrivate::setContentPositionHelper(const QPointF &deltaPos)
 
     qDebug() << "oldOver: " << oldOvershootY << "  newOver: " << newOvershootY;
     // -- x axis
-    if (oldOvershootX && (qSign(oldOvershootX) != qSign(newOvershootX))) {
+    if (scrollToX && qSign(oldScrollToDist.x()) != qSign(newScrollToDist.x())) {
+        newClampedPos.setX(scrollToPosition.x());
+        releaseVelocity.setX(0);
+        scrollToX = false;
+
+    } else if (oldOvershootX && (qSign(oldOvershootX) != qSign(newOvershootX))) {
         newClampedPos.setX((oldOvershootX < 0) ? 0 : maxPos.x());
         realOvershootDistance.setX(0);
         releaseVelocity.setX(0);
@@ -1012,15 +1033,15 @@ void QKineticScrollerPrivate::setContentPositionHelper(const QPointF &deltaPos)
             overshootX = true;
         }
         realOvershootDistance.setX(newOvershootX);
-
-    } else if (scrollToX && qSign(oldScrollToDist.x()) != qSign(newScrollToDist.x())) {
-        newClampedPos.setX(scrollToPosition.x());
-        releaseVelocity.setX(0);
-        scrollToX = false;
     }
 
     // -- y axis
-    if (oldOvershootY && (qSign(oldOvershootY) != qSign(newOvershootY))) {
+    if (scrollToY && qSign(oldScrollToDist.y()) != qSign(newScrollToDist.y())) {
+        newClampedPos.setY(scrollToPosition.y());
+        releaseVelocity.setY(0);
+        scrollToY = false;
+
+    } else if (oldOvershootY && (qSign(oldOvershootY) != qSign(newOvershootY))) {
         newClampedPos.setY((oldOvershootY < 0) ? 0 : maxPos.y());
         realOvershootDistance.setY(0);
         releaseVelocity.setY(0);
@@ -1035,11 +1056,6 @@ void QKineticScrollerPrivate::setContentPositionHelper(const QPointF &deltaPos)
             overshootY = true;
         }
         realOvershootDistance.setY(newOvershootY);
-
-    } else if (scrollToY && qSign(oldScrollToDist.y()) != qSign(newScrollToDist.y())) {
-        newClampedPos.setY(scrollToPosition.y());
-        releaseVelocity.setY(0);
-        scrollToY = false;
     }
 
     overshootPosition = realOvershootDistance;
@@ -1059,7 +1075,8 @@ void QKineticScrollerPrivate::setContentPositionHelper(const QPointF &deltaPos)
 
     q->setContentPosition(newClampedPos, realOvershootDistance);
 
-    qDebug() << "setContentPositionHelper" << newClampedPos << " overshoot:" << realOvershootDistance;
+    qDebug() << "setContentPositionHelper" << newClampedPos << " overshoot:" << realOvershootDistance <<
+    "Overshoot: "<<overshootX<<","<<overshootY<<"ScrollTo:"<<scrollToX<<","<<scrollToY;
 }