When flicking with snap, bias towards moving at least one item.

Task-number: QTBUG-8839

2 files changed, 19 insertions, 14 deletions

diff --git a/src/declarative/graphicsitems/qdeclarativegridview.cpp b/src/declarative/graphicsitems/qdeclarativegridview.cpp
index 60ffbe2..f35b903 100644
--- a/src/declarative/graphicsitems/qdeclarativegridview.cpp
+++ b/src/declarative/graphicsitems/qdeclarativegridview.cpp
@@ -755,14 +755,15 @@ void QDeclarativeGridViewPrivate::fixup(AxisData &data, qreal minExtent, qreal m
             vTime = timeline.time();
         }
     } else if (snapMode != QDeclarativeGridView::NoSnap) {
-        qreal pos = qMax(qMin(snapPosAt(position()) - highlightRangeStart, -maxExtent), -minExtent);
-        qreal dist = qAbs(data.move + pos);
+        qreal pos = -snapPosAt(-(data.move.value() - highlightRangeStart)) + highlightRangeStart;
+        pos = qMin(qMax(pos, maxExtent), minExtent);
+        qreal dist = qAbs(data.move.value() - pos);
         if (dist > 0) {
             timeline.reset(data.move);
             if (fixupDuration)
-                timeline.move(data.move, -pos, QEasingCurve(QEasingCurve::InOutQuad), fixupDuration/2);
+                timeline.move(data.move, pos, QEasingCurve(QEasingCurve::InOutQuad), fixupDuration/2);
             else
-                data.move.setValue(-pos);
+                data.move.setValue(pos);
             vTime = timeline.time();
         }
     } else {
@@ -788,7 +789,7 @@ void QDeclarativeGridViewPrivate::flick(AxisData &data, qreal minExtent, qreal m
             if (FxGridItem *item = firstVisibleItem())
                 maxDistance = qAbs(item->rowPos() + data.move.value());
         } else if (data.move.value() < minExtent) {
-            maxDistance = qAbs(minExtent - data.move.value() + (overShoot?overShootDistance(velocity, vSize):0));
+            maxDistance = qAbs(minExtent - data.move.value());
         }
         if (snapMode != QDeclarativeGridView::SnapToRow && highlightRange != QDeclarativeGridView::StrictlyEnforceRange)
             data.flickTarget = minExtent;
@@ -797,7 +798,7 @@ void QDeclarativeGridViewPrivate::flick(AxisData &data, qreal minExtent, qreal m
             qreal pos = snapPosAt(-data.move.value()) + rowSize();
             maxDistance = qAbs(pos + data.move.value());
         } else if (data.move.value() > maxExtent) {
-            maxDistance = qAbs(maxExtent - data.move.value()) + (overShoot?overShootDistance(velocity, vSize):0);
+            maxDistance = qAbs(maxExtent - data.move.value());
         }
         if (snapMode != QDeclarativeGridView::SnapToRow && highlightRange != QDeclarativeGridView::StrictlyEnforceRange)
             data.flickTarget = maxExtent;
@@ -816,7 +817,8 @@ void QDeclarativeGridViewPrivate::flick(AxisData &data, qreal minExtent, qreal m
         qreal maxAccel = v2 / (2.0f * maxDistance);
         qreal overshootDist = 0.0;
         if (maxAccel < accel) {
-            qreal dist = v2 / (accel * 2.0);
+            // + rowSize()/4 to encourage moving at least one item in the flick direction
+            qreal dist = v2 / (accel * 2.0) + rowSize()/4;
             if (v > 0)
                 dist = -dist;
             data.flickTarget = -snapPosAt(-(data.move.value() - highlightRangeStart) + dist) + highlightRangeStart;
diff --git a/src/declarative/graphicsitems/qdeclarativelistview.cpp b/src/declarative/graphicsitems/qdeclarativelistview.cpp
index d54bb70..73fe1e4 100644
--- a/src/declarative/graphicsitems/qdeclarativelistview.cpp
+++ b/src/declarative/graphicsitems/qdeclarativelistview.cpp
@@ -1124,7 +1124,7 @@ void QDeclarativeListViewPrivate::flick(AxisData &data, qreal minExtent, qreal m
             if (FxListItem *item = firstVisibleItem())
                 maxDistance = qAbs(item->position() + data.move.value());
         } else if (data.move.value() < minExtent) {
-            maxDistance = qAbs(minExtent - data.move.value() + (overShoot?overShootDistance(velocity, vSize):0));
+            maxDistance = qAbs(minExtent - data.move.value());
         }
         if (snapMode != QDeclarativeListView::SnapToItem && highlightRange != QDeclarativeListView::StrictlyEnforceRange)
             data.flickTarget = minExtent;
@@ -1133,7 +1133,7 @@ void QDeclarativeListViewPrivate::flick(AxisData &data, qreal minExtent, qreal m
             if (FxListItem *item = nextVisibleItem())
                 maxDistance = qAbs(item->position() + data.move.value());
         } else if (data.move.value() > maxExtent) {
-            maxDistance = qAbs(maxExtent - data.move.value()) + (overShoot?overShootDistance(velocity, vSize):0);
+            maxDistance = qAbs(maxExtent - data.move.value());
         }
         if (snapMode != QDeclarativeListView::SnapToItem && highlightRange != QDeclarativeListView::StrictlyEnforceRange)
             data.flickTarget = maxExtent;
@@ -1156,7 +1156,8 @@ void QDeclarativeListViewPrivate::flick(AxisData &data, qreal minExtent, qreal m
             qreal v2 = v * v;
             qreal maxAccel = v2 / (2.0f * maxDistance);
             if (maxAccel < accel) {
-                qreal dist = v2 / (accel * 2.0);
+                // + averageSize/4 to encourage moving at least one item in the flick direction
+                qreal dist = v2 / (accel * 2.0) + averageSize/4;
                 if (v > 0)
                     dist = -dist;
                 data.flickTarget = -snapPosAt(-(data.move.value() - highlightRangeStart) + dist) + highlightRangeStart;
@@ -1166,6 +1167,7 @@ void QDeclarativeListViewPrivate::flick(AxisData &data, qreal minExtent, qreal m
             } else {
                 data.flickTarget = velocity > 0 ? minExtent : maxExtent;
                 overshootDist = overShoot ? overShootDistance(v, vSize) : 0;
+                qDebug() << "boundary" << overshootDist;
             }
             timeline.reset(data.move);
             timeline.accel(data.move, v, accel, maxDistance + overshootDist);
@@ -1956,10 +1958,11 @@ void QDeclarativeListView::viewportMoved()
         if (d->haveHighlightRange && d->highlightRange == StrictlyEnforceRange && d->highlight) {
             // reposition highlight
             qreal pos = d->highlight->position();
-            if (pos > d->position() + d->highlightRangeEnd - 1 - d->highlight->size())
-                pos = d->position() + d->highlightRangeEnd - 1 - d->highlight->size();
-            if (pos < d->position() + d->highlightRangeStart)
-                pos = d->position() + d->highlightRangeStart;
+            qreal viewPos = qRound(d->position());
+            if (pos > viewPos + d->highlightRangeEnd - 1 - d->highlight->size())
+                pos = viewPos + d->highlightRangeEnd - 1 - d->highlight->size();
+            if (pos < viewPos + d->highlightRangeStart)
+                pos = viewPos + d->highlightRangeStart;
             d->highlight->setPosition(pos);
 
             // update current index