Added visual DnD indicator for left to right flow in QListView

Extended the behaviour already present in QAbstractItemView into
QListView. This means some code duplication which should maybe be refactored
at some point. (Seems to be the price to pay when some delegate does almost
the same thing as the base class).

No auto-test, as it's a drag-and-drop related task.

Reviewed-by: Thierry
Task-number: QTBUG-3730

4 files changed, 119 insertions, 3 deletions

diff --git a/src/gui/itemviews/qabstractitemview.h b/src/gui/itemviews/qabstractitemview.h
index b4f0957..f438148 100644
--- a/src/gui/itemviews/qabstractitemview.h
+++ b/src/gui/itemviews/qabstractitemview.h
@@ -361,6 +361,7 @@ private:
 
     friend class QTreeViewPrivate; // needed to compile with MSVC
     friend class QAccessibleItemRow;
+    friend class QListModeViewBase;
 };
 
 Q_DECLARE_OPERATORS_FOR_FLAGS(QAbstractItemView::EditTriggers)
diff --git a/src/gui/itemviews/qabstractitemview_p.h b/src/gui/itemviews/qabstractitemview_p.h
index fcf381a..66b7662 100644
--- a/src/gui/itemviews/qabstractitemview_p.h
+++ b/src/gui/itemviews/qabstractitemview_p.h
@@ -164,7 +164,8 @@ public:
     }
 
 #ifndef QT_NO_DRAGANDDROP
-    QAbstractItemView::DropIndicatorPosition position(const QPoint &pos, const QRect &rect, const QModelIndex &idx) const;
+    virtual QAbstractItemView::DropIndicatorPosition position(const QPoint &pos, const QRect &rect, const QModelIndex &idx) const;
+
     inline bool canDecode(QDropEvent *e) const {
         QStringList modelTypes = model->mimeTypes();
         const QMimeData *mime = e->mimeData();
diff --git a/src/gui/itemviews/qlistview.cpp b/src/gui/itemviews/qlistview.cpp
index f58f458..109d760 100644
--- a/src/gui/itemviews/qlistview.cpp
+++ b/src/gui/itemviews/qlistview.cpp
@@ -853,8 +853,13 @@ void QListView::resizeEvent(QResizeEvent *e)
 */
 void QListView::dragMoveEvent(QDragMoveEvent *e)
 {
-    if (!d_func()->commonListView->filterDragMoveEvent(e))
-        QAbstractItemView::dragMoveEvent(e);
+    Q_D(QListView);
+    if (!d->commonListView->filterDragMoveEvent(e)) {
+        if (viewMode() == QListView::ListMode && flow() == QListView::LeftToRight)
+            static_cast<QListModeViewBase *>(d->commonListView)->dragMoveEvent(e);
+        else
+            QAbstractItemView::dragMoveEvent(e);
+    }
 }
 
 
@@ -1804,6 +1809,16 @@ QItemSelection QListViewPrivate::selection(const QRect &rect) const
     return selection;
 }
 
+#ifndef QT_NO_DRAGANDDROP
+QAbstractItemView::DropIndicatorPosition QListViewPrivate::position(const QPoint &pos, const QRect &rect, const QModelIndex &idx) const
+{
+    if (viewMode == QListView::ListMode && flow == QListView::LeftToRight)
+        return static_cast<QListModeViewBase *>(commonListView)->position(pos, rect, idx);
+    else
+        return QAbstractItemViewPrivate::position(pos, rect, idx);
+}
+#endif
+
 /*
  * Common ListView Implementation
 */
@@ -1893,6 +1908,96 @@ void QListModeViewBase::paintDragDrop(QPainter *painter)
     // in IconMode, it makes no sense to show it
     dd->paintDropIndicator(painter);
 }
+
+QAbstractItemView::DropIndicatorPosition QListModeViewBase::position(const QPoint &pos, const QRect &rect, const QModelIndex &index) const
+{
+    QAbstractItemView::DropIndicatorPosition r = QAbstractItemView::OnViewport;
+    if (!dd->overwrite) {
+        const int margin = 2;
+        if (pos.x() - rect.left() < margin) {
+            r = QAbstractItemView::AboveItem;   // Visually, on the left
+        } else if (rect.right() - pos.x() < margin) {
+            r = QAbstractItemView::BelowItem;   // Visually, on the right
+        } else if (rect.contains(pos, true)) {
+            r = QAbstractItemView::OnItem;
+        }
+    } else {
+        QRect touchingRect = rect;
+        touchingRect.adjust(-1, -1, 1, 1);
+        if (touchingRect.contains(pos, false)) {
+            r = QAbstractItemView::OnItem;
+        }
+    }
+
+    if (r == QAbstractItemView::OnItem && (!(dd->model->flags(index) & Qt::ItemIsDropEnabled)))
+        r = pos.x() < rect.center().x() ? QAbstractItemView::AboveItem : QAbstractItemView::BelowItem;
+
+    return r;
+}
+
+void QListModeViewBase::dragMoveEvent(QDragMoveEvent *event)
+{
+    if (qq->dragDropMode() == QAbstractItemView::InternalMove
+        && (event->source() != qq || !(event->possibleActions() & Qt::MoveAction)))
+        return;
+
+    // ignore by default
+    event->ignore();
+
+    QModelIndex index = qq->indexAt(event->pos());
+    dd->hover = index;
+    if (!dd->droppingOnItself(event, index)
+        && dd->canDecode(event)) {
+
+        if (index.isValid() && dd->showDropIndicator) {
+            QRect rect = qq->visualRect(index);
+            dd->dropIndicatorPosition = position(event->pos(), rect, index);
+            switch (dd->dropIndicatorPosition) {
+            case QAbstractItemView::AboveItem:
+                if (dd->isIndexDropEnabled(index.parent())) {
+                    dd->dropIndicatorRect = QRect(rect.left(), rect.top(), 0, rect.height());
+                    event->accept();
+                } else {
+                    dd->dropIndicatorRect = QRect();
+                }
+                break;
+            case QAbstractItemView::BelowItem:
+                if (dd->isIndexDropEnabled(index.parent())) {
+                    dd->dropIndicatorRect = QRect(rect.right(), rect.top(), 0, rect.height());
+                    event->accept();
+                } else {
+                    dd->dropIndicatorRect = QRect();
+                }
+                break;
+            case QAbstractItemView::OnItem:
+                if (dd->isIndexDropEnabled(index)) {
+                    dd->dropIndicatorRect = rect;
+                    event->accept();
+                } else {
+                    dd->dropIndicatorRect = QRect();
+                }
+                break;
+            case QAbstractItemView::OnViewport:
+                dd->dropIndicatorRect = QRect();
+                if (dd->isIndexDropEnabled(qq->rootIndex())) {
+                    event->accept(); // allow dropping in empty areas
+                }
+                break;
+            }
+        } else {
+            dd->dropIndicatorRect = QRect();
+            dd->dropIndicatorPosition = QAbstractItemView::OnViewport;
+            if (dd->isIndexDropEnabled(qq->rootIndex())) {
+                event->accept(); // allow dropping in empty areas
+            }
+        }
+        dd->viewport->update();
+    } // can decode
+
+    if (dd->shouldAutoScroll(event->pos()))
+        qq->startAutoScroll();
+}
+
 #endif //QT_NO_DRAGANDDROP
 
 void QListModeViewBase::updateVerticalScrollBar(const QSize &step)
diff --git a/src/gui/itemviews/qlistview_p.h b/src/gui/itemviews/qlistview_p.h
index de4c7f3..3f8f9db 100644
--- a/src/gui/itemviews/qlistview_p.h
+++ b/src/gui/itemviews/qlistview_p.h
@@ -231,6 +231,11 @@ public:
 
 #ifndef QT_NO_DRAGANDDROP
     void paintDragDrop(QPainter *painter);
+
+    // The next two methods are to be used on LefToRight flow only.
+    // WARNING: Plenty of duplicated code from QAbstractItemView{,Private}.
+    QAbstractItemView::DropIndicatorPosition position(const QPoint &pos, const QRect &rect, const QModelIndex &idx) const;
+    void dragMoveEvent(QDragMoveEvent *e);
 #endif
 
 private:
@@ -356,6 +361,10 @@ public:
     QItemSelection selection(const QRect &rect) const;
     void selectAll(QItemSelectionModel::SelectionFlags command);
 
+#ifndef QT_NO_DRAGANDDROP
+    virtual QAbstractItemView::DropIndicatorPosition position(const QPoint &pos, const QRect &rect, const QModelIndex &idx) const;
+#endif
+
     inline void setGridSize(const QSize &size) { grid = size; }
     inline QSize gridSize() const { return grid; }
     inline void setWrapping(bool b) { wrap = b; }