Re-implement dropping of files on folders in the Places Panel.

This resolves a regression caused by the Places Panel rewrite. There is
a small glitch left when reordering items (dragging below the last or
above the first item only shows the drop indicator when first dragging
out of the item and then back), but I prefer not to fix this glitch
right now because this would require a more intrusive change, and I do
not want to risk regressions because is not much time left to fix them
before 4.9.0 is released.

Thanks to Peter Penz for providing some advice about this issue.

CCBUG: 302557

src/kitemviews/kitemlistcontroller.cpp

@@ -778,7 +778,6 @@ bool KItemListController::dragLeaveEvent(QGraphicsSceneDragDropEvent* event, con
 
 bool KItemListController::dragMoveEvent(QGraphicsSceneDragDropEvent* event, const QTransform& transform)
 {
-    Q_UNUSED(transform);
     if (!m_model || !m_view) {
         return false;
     }
@@ -799,15 +798,17 @@ bool KItemListController::dragMoveEvent(QGraphicsSceneDragDropEvent* event, cons
         }
 
         if (newHoveredWidget) {
-            const int index = newHoveredWidget->index();
-            if (m_model->supportsDropping(index)) {
-                newHoveredWidget->setHovered(true);
-            } else if (m_model->sortRole().isEmpty()) {
-                // The model supports inserting of items on
-                // the given index. Assure that a drop-indicator
-                // is shown by the view.
-                m_view->showDropIndicator(pos);
+            bool droppingBetweenItems = false;
+            if (m_model->sortRole().isEmpty()) {
+                // The model supports inserting items between other items.
+                droppingBetweenItems = (m_view->showDropIndicator(pos) >= 0);
             }
+
+            const int index = newHoveredWidget->index();
+            if (!droppingBetweenItems && m_model->supportsDropping(index)) {
+                // Something has been dragged on an item.
+                m_view->hideDropIndicator();
+                newHoveredWidget->setHovered(true);
                 emit itemHovered(index);
 
                 if (m_autoActivationTimer->interval() >= 0) {
@@ -816,13 +817,13 @@ bool KItemListController::dragMoveEvent(QGraphicsSceneDragDropEvent* event, cons
                 }
             }
         }
+    }
 
     return false;
 }
 
 bool KItemListController::dropEvent(QGraphicsSceneDragDropEvent* event, const QTransform& transform)
 {
-    Q_UNUSED(transform)
     if (!m_view) {
         return false;
     }
@@ -831,13 +832,19 @@ bool KItemListController::dropEvent(QGraphicsSceneDragDropEvent* event, const QT
     m_view->setAutoScroll(false);
 
     const QPointF pos = transform.map(event->pos());
+
+    int dropAboveIndex = -1;
     if (m_model->sortRole().isEmpty()) {
-        // The model supports inserting of items on
-        // a given index.
-        const int dropIndex = m_view->showDropIndicator(pos);
+        // The model supports inserting of items between other items.
+        dropAboveIndex = m_view->showDropIndicator(pos);
+    }
+
+    if (dropAboveIndex >= 0) {
+        // Something has been dropped between two items.
         m_view->hideDropIndicator();
-        emit itemDropEvent(dropIndex, event);
+        emit aboveItemDropEvent(dropAboveIndex, event);
     } else {
+        // Something has been dropped on an item or on an empty part of the view.
         emit itemDropEvent(m_view->itemAt(pos), event);
     }
 

src/kitemviews/kitemlistcontroller.h

@@ -201,9 +201,18 @@ signals:
      * Is emitted if a drop event is done above the item with the index
      * \a index. If \a index is < 0 the drop event is done above an
      * empty area of the view.
+     * TODO: Introduce a new signal viewDropEvent(QGraphicsSceneDragDropEvent),
+     *       which is emitted if the drop event occurs on an empty area in
+     *       the view, and make sure that index is always >= 0 in itemDropEvent().
      */
     void itemDropEvent(int index, QGraphicsSceneDragDropEvent* event);
 
+    /**
+     * Is emitted if a drop event is done between the item with the index
+     * \a index and the previous item.
+     */
+    void aboveItemDropEvent(int index, QGraphicsSceneDragDropEvent* event);
+
     void modelChanged(KItemModelBase* current, KItemModelBase* previous);
     void viewChanged(KItemListView* current, KItemListView* previous);
 

src/kitemviews/kitemlistview.cpp

@@ -2318,6 +2318,13 @@ int KItemListView::showDropIndicator(const QPointF& pos)
         const QPointF mappedPos = widget->mapFromItem(this, pos);
         const QRectF rect = itemRect(widget->index());
         if (mappedPos.y() >= 0 && mappedPos.y() <= rect.height()) {
+            if (m_model->supportsDropping(widget->index())) {
+                const int gap = qMax(4, m_styleOption.padding);
+                if (mappedPos.y() >= gap && mappedPos.y() <= rect.height() - gap) {
+                    return -1;
+                }
+            }
+
             const bool isAboveItem = (mappedPos.y () < rect.height() / 2);
             const qreal y = isAboveItem ? rect.top() : rect.bottom();
 

src/panels/places/placesitemlistwidget.cpp

@@ -19,6 +19,8 @@
 
 #include "placesitemlistwidget.h"
 
+#include "kdebug.h"
+
 PlacesItemListWidget::PlacesItemListWidget(KItemListWidgetInformant* informant, QGraphicsItem* parent) :
     KStandardItemListWidget(informant, parent)
 {

src/panels/places/placesitemmodel.cpp

@@ -396,7 +396,12 @@ QMimeData* PlacesItemModel::createMimeData(const QSet<int>& indexes) const
     return mimeData;
 }
 
-void PlacesItemModel::dropMimeData(int index, const QMimeData* mimeData)
+bool PlacesItemModel::supportsDropping(int index) const
+{
+    return index >= 0 && index < count();
+}
+
+void PlacesItemModel::dropMimeDataBefore(int index, const QMimeData* mimeData)
 {
     if (mimeData->hasFormat(internalMimeType())) {
         // The item has been moved inside the view

src/panels/places/placesitemmodel.h

@@ -120,7 +120,10 @@ public:
     /** @reimp */
     virtual QMimeData* createMimeData(const QSet<int>& indexes) const;
 
-    void dropMimeData(int index, const QMimeData* mimeData);
+    /** @reimp */
+    virtual bool supportsDropping(int index) const;
+
+    void dropMimeDataBefore(int index, const QMimeData* mimeData);
 
     /**
      * @return Converts the URL, which contains "virtual" URLs for system-items like

src/panels/places/placespanel.cpp

@@ -93,6 +93,7 @@ void PlacesPanel::showEvent(QShowEvent* event)
         connect(m_controller, SIGNAL(itemContextMenuRequested(int,QPointF)), this, SLOT(slotItemContextMenuRequested(int,QPointF)));
         connect(m_controller, SIGNAL(viewContextMenuRequested(QPointF)), this, SLOT(slotViewContextMenuRequested(QPointF)));
         connect(m_controller, SIGNAL(itemDropEvent(int,QGraphicsSceneDragDropEvent*)), this, SLOT(slotItemDropEvent(int,QGraphicsSceneDragDropEvent*)));
+        connect(m_controller, SIGNAL(aboveItemDropEvent(int,QGraphicsSceneDragDropEvent*)), this, SLOT(slotAboveItemDropEvent(int,QGraphicsSceneDragDropEvent*)));
 
         KItemListContainer* container = new KItemListContainer(m_controller, this);
         container->setEnabledFrame(false);
@@ -253,7 +254,23 @@ void PlacesPanel::slotViewContextMenuRequested(const QPointF& pos)
 
 void PlacesPanel::slotItemDropEvent(int index, QGraphicsSceneDragDropEvent* event)
 {
-    m_model->dropMimeData(index, event->mimeData());
+    if (index < 0) {
+        return;
+    }
+
+    KUrl destUrl = m_model->placesItem(index)->url();
+    QDropEvent dropEvent(event->pos().toPoint(),
+                         event->possibleActions(),
+                         event->mimeData(),
+                         event->buttons(),
+                         event->modifiers());
+
+    DragAndDropHelper::dropUrls(KFileItem(), destUrl, &dropEvent);
+}
+
+void PlacesPanel::slotAboveItemDropEvent(int index, QGraphicsSceneDragDropEvent* event)
+{
+    m_model->dropMimeDataBefore(index, event->mimeData());
 }
 
 void PlacesPanel::slotUrlsDropped(const KUrl& dest, QDropEvent* event, QWidget* parent)

src/panels/places/placespanel.h

@@ -56,6 +56,7 @@ private slots:
     void slotItemContextMenuRequested(int index, const QPointF& pos);
     void slotViewContextMenuRequested(const QPointF& pos);
     void slotItemDropEvent(int index, QGraphicsSceneDragDropEvent* event);
+    void slotAboveItemDropEvent(int index, QGraphicsSceneDragDropEvent* event);
     void slotUrlsDropped(const KUrl& dest, QDropEvent* event, QWidget* parent);
     void slotTrashUpdated(KJob* job);
     void slotStorageSetupDone(int index, bool success);