Fiddling around with the kinetic scroller

3 files changed, 52 insertions, 13 deletions

diff --git a/main.cpp b/main.cpp
index f7febd6..128d69b 100644
--- a/main.cpp
+++ b/main.cpp
@@ -14,5 +14,7 @@ int main(int argc, char **argv)
     s->setWidget(lw);
     lw->show();
 
+    s->scrollTo(QPointF(80,800));
+
     return a.exec();
-}
\ No newline at end of file
+}
diff --git a/qkineticscroller.cpp b/qkineticscroller.cpp
index 04b0b83..2197ec8 100644
--- a/qkineticscroller.cpp
+++ b/qkineticscroller.cpp
@@ -190,7 +190,7 @@ void QKineticScroller::resetScrollMetrics()
     metrics.insert(FramesPerSecond, qreal(20));
 #else
     metrics.insert(DragVelocitySmoothingFactor, qreal(0.02));
-    metrics.insert(ExponentialDecelerationBase, qreal(0));
+    metrics.insert(ExponentialDecelerationBase, qreal(1));
     metrics.insert(LinearDecelerationFactor, qreal(0.38));
     metrics.insert(OvershootSpringConstant, qreal(15.0));
     metrics.insert(OvershootDragResistanceFactor, qreal(0.5));
@@ -712,12 +712,10 @@ void QKineticScrollerPrivate::timerEventWhileScrolling(qint64 time_ms)
         if (overshootDistance.x() && ((overshootDistance.x() > 0) != (newOvershootDistance.x() > 0))) {
             overshootDistance.setX(0);
             velocity.setX(0);
-            scrollToX = false;
         }
         if (overshootDistance.y() && ((overshootDistance.y() > 0) != (newOvershootDistance.y() > 0))) {
             overshootDistance.setY(0);
             velocity.setY(0);
-            scrollToY = false;
         }
     }
 
@@ -739,11 +737,14 @@ void QKineticScrollerPrivate::timerEventWhileScrolling(qint64 time_ms)
         velocity.setX(qBound(-overshootMaximumVelocity, velocity.x(), overshootMaximumVelocity));
 
     } else if (scrollToX) {
-        if (qAbs(velocity.x()) >= qreal(3.0 / 1000 /* 3mm/s */))
+        if (qAbs(velocity.x()) * exponentialDecelerationPerFrame > linearDecelerationPerFrame + qreal(30.0 / 1000) )/* 30 px/s */
             velocity.setX(decelerate(velocity.x(), exponentialDecelerationPerFrame, linearDecelerationPerFrame));
+        else
+            velocity.setX((velocity.x()<0 ? -1.0 : 1.0) * qreal(30.0 / 1000));
 
         // - target reached?
         qreal dist = scrollToPosition.x() - q->contentPosition().x();
+qDebug() << "scroll to x" << scrollToPosition.x() << "v:"<< velocity.x() << " dist " << dist;
         if ((velocity.x() > 0.0 && dist <= 0.0) || (velocity.x() < 0.0 && dist >= 0.0)) {
             velocity.setX(0.0);
             scrollToX = false;
@@ -759,11 +760,14 @@ void QKineticScrollerPrivate::timerEventWhileScrolling(qint64 time_ms)
         velocity.setY(qBound(-overshootMaximumVelocity, velocity.y(), overshootMaximumVelocity));
 
     } else if (scrollToY) {
-        if (qAbs(velocity.y()) >= qreal(3.0 / 1000 /* 3mm/s */))
+        if (qAbs(velocity.y()) * exponentialDecelerationPerFrame > linearDecelerationPerFrame + qreal(30.0 / 1000) )/* 30 px/s */
             velocity.setY(decelerate(velocity.y(), exponentialDecelerationPerFrame, linearDecelerationPerFrame));
+        else
+            velocity.setY((velocity.y()<0 ? -1.0 : 1.0) * qreal(30.0 / 1000));
 
         // - target reached?
         qreal dist = scrollToPosition.y() - q->contentPosition().y();
+qDebug() << "scroll to y" << scrollToPosition.y() << "v:"<< velocity.y() << " dist " << dist;
         if ((velocity.y() > 0.0 && dist <= 0.0) || (velocity.y() < 0.0 && dist >= 0.0)) {
             velocity.setY(0.0);
             scrollToY = false;
@@ -821,6 +825,8 @@ void QKineticScrollerPrivate::setState(QKineticScroller::State newstate)
             killTimer(timerId);
             timerId = 0;
         }
+        scrollToX = false;
+        scrollToY = false;
         velocity = QPointF(0, 0);
         break;
 
@@ -837,11 +843,11 @@ void QKineticScrollerPrivate::setState(QKineticScroller::State newstate)
         break;
 
     case QKineticScroller::StateScrolling:
-        if (state == QKineticScroller::StatePressed) {
+    //    if (state == QKineticScroller::StatePressed) {
             if (!timerId) {
                 timerId = startTimer(1000 / framesPerSecond);
             }
-        }
+     //   }
         scrollTimer.start();
         break;
     }
@@ -867,20 +873,45 @@ void QKineticScroller::scrollTo(const QPointF &pos, int scrollTime)
 {
     Q_D(QKineticScroller);
 
-    if ((pos == contentPosition()) || (d->state != QKineticScroller::StateInactive)) {
+    qreal time = qreal(scrollTime) / 1000;
+
+    if ((pos == contentPosition()) ||
+            (d->state == QKineticScroller::StatePressed) ||
+            (d->state == QKineticScroller::StateDragging)) {
         return;
     }
 
-    // v(t) = vstart * exponentialDecelerationBase ^ t + linearDecelerationFactor * t
+    // estimate the minimal start velocity
+    // if the start velocity is below that then the scrolling would stop before scrollTime.
+    qreal vMin = d->linearDecelerationFactor * time / qPow(d->exponentialDecelerationBase, time);
+
+    // estimate of the distance passed within the vMin time during scrollTime
+    qreal distMin = qreal(scrollTime) * vMin / 2.0;
+
+    qKSDebug() << "QAbstractKineticScroller::scrollTo v, dis(" << vMin << ", " << distMin;
+
+    QPointF v = QPointF((pos.x()-contentPosition().x()) / distMin * vMin,
+                        (pos.y()-contentPosition().y()) / distMin * vMin);
+
+    qKSDebug() << "QAbstractKineticScroller::scrollTo(" << pos << ", " << v;
+
+    // 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) -  lDF / (2 * t ^ 2)
     //
     // pos(scrollTime) = pos - contentsPos()
     // vstart = (lDF / 2 * scrollTime ^ 2 - (pos - contentPos())) * ln(eDB) / eDB ^ scrollTime
+/*
 
-    QPointF v = QPointF(1, 1) * d->linearDecelerationFactor / 2 * scrollTime * scrollTime - (pos - contentPosition()) *
+    QPointF v = QPointF(-1, -1) * d->linearDecelerationFactor / (qreal(2) * qreal(scrollTime) * qreal(scrollTime)) - (pos - contentPosition()) *
                 qLn(d->exponentialDecelerationBase) / qPow(d->exponentialDecelerationBase, scrollTime);
 
+    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);
+
+    v = QPointF(0.01, 0.01);
+*/
     // start the scrolling
     d->scrollToPosition = pos;
     d->scrollToX = true;
@@ -941,6 +972,12 @@ void QKineticScrollerPrivate::setContentPositionHelper(const QPointF &pos)
     clampedPos.setX(qBound(qreal(0), pos.x(), maxPos.x()));
     clampedPos.setY(qBound(qreal(0), pos.y(), maxPos.y()));
 
+    // -- stop scroll to if hitting boundary
+    if (clampedPos.x() != pos.x())
+        scrollToX = false;
+    if (clampedPos.y() != pos.y())
+        scrollToY = false;
+
     bool alwaysOvershoot = (overshootPolicy == QKineticScroller::OvershootAlwaysOn);
     qreal overshootX = (maxPos.x() || alwaysOvershoot) ? pos.x() - clampedPos.x() : 0;
     qreal overshootY = (maxPos.y() || alwaysOvershoot) ? pos.y() - clampedPos.y() : 0;
diff --git a/qkineticscroller.h b/qkineticscroller.h
index 3b31b88..a574891 100644
--- a/qkineticscroller.h
+++ b/qkineticscroller.h
@@ -88,7 +88,7 @@ public:
     {
         DragVelocitySmoothingFactor,             // qreal [0..1/s]  (complex calculation involving time) v = v_new* DASF + v_old * (1-DASF)
 
-        LinearDecelerationFactor,                // qreal [0..1]
+        LinearDecelerationFactor,                // qreal [m/s^2]
         ExponentialDecelerationBase,             // qreal [0..1]
         OvershootSpringConstant,                 // qreal [0..1]
         OvershootDragResistanceFactor,           // qreal [0..1]