Flickable: drag-over-bounds is not velocity-sensitive

The inspiration for velocity sensitivity was to make it feel more like
native trackpad flicking on OS X.  But on touchscreens it doesn't
make as much sense, and it became too difficult to intentionally
overshoot in applications that depend on pull-to-refresh functionality.

Task-number: QTBUG-46108
Change-Id: I3fea5324aaac1f003ead200e14b0c76bd8c0ece6
Reviewed-by: J-P Nurmi <jpnurmi@theqtcompany.com>

2 files changed, 34 insertions, 16 deletions

diff --git a/src/quick/items/qquickflickable.cpp b/src/quick/items/qquickflickable.cpp
index 52142346ab..19fb66c19c 100644
--- a/src/quick/items/qquickflickable.cpp
+++ b/src/quick/items/qquickflickable.cpp
@@ -1004,7 +1004,8 @@ void QQuickFlickablePrivate::maybeBeginDrag(qint64 currentTimestamp, const QPoin
 }
 
 void QQuickFlickablePrivate::drag(qint64 currentTimestamp, QEvent::Type eventType, const QPointF &localPos,
-                                  const QVector2D &deltas, bool overThreshold, bool momentum, const QVector2D &velocity)
+                                  const QVector2D &deltas, bool overThreshold, bool momentum,
+                                  bool velocitySensitiveOverBounds, const QVector2D &velocity)
 {
     Q_Q(QQuickFlickable);
     bool rejectY = false;
@@ -1061,9 +1062,13 @@ void QQuickFlickablePrivate::drag(qint64 currentTimestamp, QEvent::Type eventTyp
                         }
                         return;
                     }
-                    qreal overshoot = (newY - minY) * vData.velocity / QML_FLICK_DEFAULTMAXVELOCITY / QML_FLICK_OVERSHOOTFRICTION;
-                    overshoot = QML_FLICK_OVERSHOOT * devicePixelRatio() * EaseOvershoot(overshoot / QML_FLICK_OVERSHOOT / devicePixelRatio());
-                    newY = minY + overshoot;
+                    if (velocitySensitiveOverBounds) {
+                        qreal overshoot = (newY - minY) * vData.velocity / QML_FLICK_DEFAULTMAXVELOCITY / QML_FLICK_OVERSHOOTFRICTION;
+                        overshoot = QML_FLICK_OVERSHOOT * devicePixelRatio() * EaseOvershoot(overshoot / QML_FLICK_OVERSHOOT / devicePixelRatio());
+                        newY = minY + overshoot;
+                    } else {
+                        newY = minY + (newY - minY) / 2;
+                    }
                 } else if (newY < maxY && maxY - minY <= 0) {
                     // Overshoot beyond the bottom.  But don't wait for momentum phase to end before returning to bounds.
                     if (momentum && vData.atEnd) {
@@ -1073,9 +1078,13 @@ void QQuickFlickablePrivate::drag(qint64 currentTimestamp, QEvent::Type eventTyp
                         }
                         return;
                     }
-                    qreal overshoot = (newY - maxY) * vData.velocity / QML_FLICK_DEFAULTMAXVELOCITY / QML_FLICK_OVERSHOOTFRICTION;
-                    overshoot = QML_FLICK_OVERSHOOT * devicePixelRatio() * EaseOvershoot(overshoot / QML_FLICK_OVERSHOOT / devicePixelRatio());
-                    newY = maxY - overshoot;
+                    if (velocitySensitiveOverBounds) {
+                        qreal overshoot = (newY - maxY) * vData.velocity / QML_FLICK_DEFAULTMAXVELOCITY / QML_FLICK_OVERSHOOTFRICTION;
+                        overshoot = QML_FLICK_OVERSHOOT * devicePixelRatio() * EaseOvershoot(overshoot / QML_FLICK_OVERSHOOT / devicePixelRatio());
+                        newY = maxY - overshoot;
+                    } else {
+                        newY = maxY + (newY - maxY) / 2;
+                    }
                 }
             }
             if (!rejectY && stealMouse && dy != 0.0 && dy != vData.previousDragDelta) {
@@ -1126,9 +1135,13 @@ void QQuickFlickablePrivate::drag(qint64 currentTimestamp, QEvent::Type eventTyp
                         }
                         return;
                     }
-                    qreal overshoot = (newX - minX) * hData.velocity / QML_FLICK_DEFAULTMAXVELOCITY / QML_FLICK_OVERSHOOTFRICTION;
-                    overshoot = QML_FLICK_OVERSHOOT * devicePixelRatio() * EaseOvershoot(overshoot / QML_FLICK_OVERSHOOT / devicePixelRatio());
-                    newX = minX + overshoot;
+                    if (velocitySensitiveOverBounds) {
+                        qreal overshoot = (newX - minX) * hData.velocity / QML_FLICK_DEFAULTMAXVELOCITY / QML_FLICK_OVERSHOOTFRICTION;
+                        overshoot = QML_FLICK_OVERSHOOT * devicePixelRatio() * EaseOvershoot(overshoot / QML_FLICK_OVERSHOOT / devicePixelRatio());
+                        newX = minX + overshoot;
+                    } else {
+                        newX = minX + (newX - minX) / 2;
+                    }
                 } else if (newX < maxX && maxX - minX <= 0) {
                     // Overshoot beyond the right.  But don't wait for momentum phase to end before returning to bounds.
                     if (momentum && hData.atEnd) {
@@ -1138,9 +1151,13 @@ void QQuickFlickablePrivate::drag(qint64 currentTimestamp, QEvent::Type eventTyp
                         }
                         return;
                     }
-                    qreal overshoot = (newX - maxX) * hData.velocity / QML_FLICK_DEFAULTMAXVELOCITY / QML_FLICK_OVERSHOOTFRICTION;
-                    overshoot = QML_FLICK_OVERSHOOT * devicePixelRatio() * EaseOvershoot(overshoot / QML_FLICK_OVERSHOOT / devicePixelRatio());
-                    newX = maxX - overshoot;
+                    if (velocitySensitiveOverBounds) {
+                        qreal overshoot = (newX - maxX) * hData.velocity / QML_FLICK_DEFAULTMAXVELOCITY / QML_FLICK_OVERSHOOTFRICTION;
+                        overshoot = QML_FLICK_OVERSHOOT * devicePixelRatio() * EaseOvershoot(overshoot / QML_FLICK_OVERSHOOT / devicePixelRatio());
+                        newX = maxX - overshoot;
+                    } else {
+                        newX = maxX + (newX - maxX) / 2;
+                    }
                 }
             }
 
@@ -1210,7 +1227,7 @@ void QQuickFlickablePrivate::handleMouseMoveEvent(QMouseEvent *event)
     if (q->xflick())
         overThreshold |= QQuickWindowPrivate::dragOverThreshold(deltas.x(), Qt::XAxis, event);
 
-    drag(currentTimestamp, event->type(), event->localPos(), deltas, overThreshold, false, velocity);
+    drag(currentTimestamp, event->type(), event->localPos(), deltas, overThreshold, false, false, velocity);
 }
 
 void QQuickFlickablePrivate::handleMouseReleaseEvent(QMouseEvent *event)
@@ -1433,7 +1450,7 @@ void QQuickFlickable::wheelEvent(QWheelEvent *event)
         QVector2D velocity(xDelta / elapsed, yDelta / elapsed);
         d->lastPosTime = currentTimestamp;
         d->accumulatedWheelPixelDelta += QVector2D(event->pixelDelta());
-        d->drag(currentTimestamp, event->type(), event->posF(), d->accumulatedWheelPixelDelta, true, !d->scrollingPhase, velocity);
+        d->drag(currentTimestamp, event->type(), event->posF(), d->accumulatedWheelPixelDelta, true, !d->scrollingPhase, true, velocity);
     }
 
     if (!event->isAccepted())
diff --git a/src/quick/items/qquickflickable_p_p.h b/src/quick/items/qquickflickable_p_p.h
index d7148ca57a..65bb3e802d 100644
--- a/src/quick/items/qquickflickable_p_p.h
+++ b/src/quick/items/qquickflickable_p_p.h
@@ -250,7 +250,8 @@ public:
 
     void maybeBeginDrag(qint64 currentTimestamp, const QPointF &pressPosn);
     void drag(qint64 currentTimestamp, QEvent::Type eventType, const QPointF &localPos,
-              const QVector2D &deltas, bool overThreshold, bool momentum, const QVector2D &velocity);
+              const QVector2D &deltas, bool overThreshold, bool momentum,
+              bool velocitySensitiveOverBounds, const QVector2D &velocity);
 
     qint64 computeCurrentTime(QInputEvent *event);
     qreal devicePixelRatio();