Add SnapPosition mode to positionViewAtIndex() in List/GridView.

This allows the view to be positioned on a snap boundary, which is
generally what is wanted when strict highlight mode s set or snapping
is enabled.

Task-number: QTBUG-26605
Change-Id: I6288dc8be4ff16c412b56ab449b6a9fb7b7ea889
Reviewed-by: Bea Lam <bea.lam@nokia.com>

4 files changed, 32 insertions, 2 deletions

diff --git a/src/quick/items/qquickgridview.cpp b/src/quick/items/qquickgridview.cpp
index 8f330b9031..518692a813 100644
--- a/src/quick/items/qquickgridview.cpp
+++ b/src/quick/items/qquickgridview.cpp
@@ -2490,6 +2490,9 @@ bool QQuickGridViewPrivate::needsRefillForAddedOrRemovedIndex(int modelIndex) co
     bring the item into view.
     \li GridView.Contain - ensure the entire item is visible.  If the item is larger than
     the view the item is positioned at the top (or left for \c GridView.TopToBottom flow) of the view.
+    \li GridView.SnapPosition - position the item at \l preferredHighlightBegin.  This mode
+    is only valid if \l highlightRangeMode is StrictlyEnforceRange or snapping is enabled
+    via \l snapMode.
     \endlist
 
     If positioning the view at the index would cause empty space to be displayed at
diff --git a/src/quick/items/qquickitemview.cpp b/src/quick/items/qquickitemview.cpp
index 8f1687f4e6..240027e312 100644
--- a/src/quick/items/qquickitemview.cpp
+++ b/src/quick/items/qquickitemview.cpp
@@ -613,6 +613,10 @@ void QQuickItemView::setHighlightRangeMode(HighlightRangeMode mode)
         return;
     d->highlightRange = mode;
     d->haveHighlightRange = d->highlightRange != NoHighlightRange && d->highlightRangeStart <= d->highlightRangeEnd;
+    if (isComponentComplete()) {
+        d->updateViewport();
+        d->fixupPosition();
+    }
     emit highlightRangeModeChanged();
 }
 
@@ -631,6 +635,10 @@ void QQuickItemView::setPreferredHighlightBegin(qreal start)
         return;
     d->highlightRangeStart = start;
     d->haveHighlightRange = d->highlightRange != NoHighlightRange && d->highlightRangeStart <= d->highlightRangeEnd;
+    if (isComponentComplete()) {
+        d->updateViewport();
+        d->fixupPosition();
+    }
     emit preferredHighlightBeginChanged();
 }
 
@@ -641,6 +649,10 @@ void QQuickItemView::resetPreferredHighlightBegin()
     if (d->highlightRangeStart == 0)
         return;
     d->highlightRangeStart = 0;
+    if (isComponentComplete()) {
+        d->updateViewport();
+        d->fixupPosition();
+    }
     emit preferredHighlightBeginChanged();
 }
 
@@ -658,6 +670,10 @@ void QQuickItemView::setPreferredHighlightEnd(qreal end)
         return;
     d->highlightRangeEnd = end;
     d->haveHighlightRange = d->highlightRange != NoHighlightRange && d->highlightRangeStart <= d->highlightRangeEnd;
+    if (isComponentComplete()) {
+        d->updateViewport();
+        d->fixupPosition();
+    }
     emit preferredHighlightEndChanged();
 }
 
@@ -668,6 +684,10 @@ void QQuickItemView::resetPreferredHighlightEnd()
     if (d->highlightRangeEnd == 0)
         return;
     d->highlightRangeEnd = 0;
+    if (isComponentComplete()) {
+        d->updateViewport();
+        d->fixupPosition();
+    }
     emit preferredHighlightEndChanged();
 }
 
@@ -819,7 +839,7 @@ void QQuickItemViewPrivate::positionViewAtIndex(int index, int mode)
     Q_Q(QQuickItemView);
     if (!isValid())
         return;
-    if (mode < QQuickItemView::Beginning || mode > QQuickItemView::Contain)
+    if (mode < QQuickItemView::Beginning || mode > QQuickItemView::SnapPosition)
         return;
 
     applyPendingChanges();
@@ -871,6 +891,10 @@ void QQuickItemViewPrivate::positionViewAtIndex(int index, int mode)
                 pos = itemPos - size() + item->size();
             if (itemPos < pos)
                 pos = itemPos;
+            break;
+        case QQuickItemView::SnapPosition:
+            pos = itemPos - highlightRangeStart;
+            break;
         }
         pos = qMin(pos, maxExtent);
         qreal minExtent;
diff --git a/src/quick/items/qquickitemview_p.h b/src/quick/items/qquickitemview_p.h
index e1cb02070d..75d573c930 100644
--- a/src/quick/items/qquickitemview_p.h
+++ b/src/quick/items/qquickitemview_p.h
@@ -199,7 +199,7 @@ public:
     int highlightMoveDuration() const;
     virtual void setHighlightMoveDuration(int);
 
-    enum PositionMode { Beginning, Center, End, Visible, Contain };
+    enum PositionMode { Beginning, Center, End, Visible, Contain, SnapPosition };
 
     Q_INVOKABLE void positionViewAtIndex(int index, int mode);
     Q_INVOKABLE int indexAt(qreal x, qreal y) const;
diff --git a/src/quick/items/qquicklistview.cpp b/src/quick/items/qquicklistview.cpp
index 18b994733e..61574ee1b1 100644
--- a/src/quick/items/qquicklistview.cpp
+++ b/src/quick/items/qquicklistview.cpp
@@ -3031,6 +3031,9 @@ void QQuickListViewPrivate::translateAndTransitionItemsAfter(int afterModelIndex
     bring the item into view.
     \li ListView.Contain - ensure the entire item is visible.  If the item is larger than
     the view the item is positioned at the top (or left for horizontal orientation) of the view.
+    \li ListView.SnapPosition - position the item at \l preferredHighlightBegin.  This mode
+    is only valid if \l highlightRangeMode is StrictlyEnforceRange or snapping is enabled
+    via \l snapMode.
     \endlist
 
     If positioning the view at \a index would cause empty space to be displayed at