Update the QtGraphicsTreeView::doLayout() to a slightly improved algorithm. It is still not optimal and is still a work-in-progress.

3 files changed, 33 insertions, 49 deletions

diff --git a/src/qgraphicstreeview.cpp b/src/qgraphicstreeview.cpp
index cc24969..85490cd 100644
--- a/src/qgraphicstreeview.cpp
+++ b/src/qgraphicstreeview.cpp
@@ -335,18 +335,17 @@ void QtGraphicsTreeViewPrivate::_q_reset()
 void QtGraphicsTreeViewPrivate::_q_selectionsChanged(const QtTreeSelection &selection)
 {
     //qDebug() << "QtGraphicsTreeViewPrivate::_q_selectionsChanged" << selection;
-    for (int i = 0; i < items.count(); ++i)
-        if (selection.contains(items.at(i)->iterator()))
-            items.at(i)->update();
+    // ### FIXME: it might be more efficient to iterate over the items instead
+    QtTreeSelection::const_iterator it = selection.constBegin();
+    for (; it != selection.constEnd(); ++it)
+        updateItem(*it);
 }
 
 void QtGraphicsTreeViewPrivate::_q_currentChanged(const QtTreeModelBase::iterator_base &current, const QtTreeModelBase::iterator_base &previous)
 {
-    //Q_Q(QtGraphicsTreeView);
-    Q_UNUSED(current);
-    Q_UNUSED(previous);
     //qDebug() << "QtGraphicsTreeViewPrivate::_q_currentChanged" << current << previous;
-    //q->update(); // ### FIXME: remove when converted to items
+    updateItem(current);
+    updateItem(previous);
 }
 
 /*!
@@ -712,29 +711,10 @@ void QtGraphicsTreeViewPrivate::_q_mapIndexesToItems()
 /*!
   \internal
  */
-void QtGraphicsTreeViewPrivate::scrollItems(QtTreeModelBase::iterator_base it, QStack<QtTreeModelBase::iterator_base> stack, int index)
-{
-    // shift items around
-    Q_ASSERT(it.isValid());
-    if (!items.isEmpty()) {
-        // scrolling down - move from first to last
-        while (items.first()->index() < index) {
-            const QtGraphicsTreeViewItem *last = items.last();
-            QtTreeModelIterator iterator = last->iterator();
-            next(iterator, stack);
-            Q_ASSERT(iterator.isValid());
-            items.append(creator->reassign(iterator, last->index() + 1, items.takeFirst()));
-        }
-        // scrolling up - move from last to first
-        const int firstNonVisibleIndex = index + items.count();
-        while (items.last()->index() >= firstNonVisibleIndex) {
-            const QtGraphicsTreeViewItem *first = items.first();
-            QtTreeModelIterator iterator = first->iterator();
-            previous(iterator, stack);
-            Q_ASSERT(iterator.isValid());
-            items.prepend(creator->reassign(iterator, first->index() - 1, items.takeLast()));
-        }
-    }
+void QtGraphicsTreeViewPrivate::updateItem(const QtTreeModelBase::iterator_base &it) const
+{
+    if (QtGraphicsTreeViewItem *item = items.value(it))
+        item->update();
 }
 
 // QtGraphicsTreeView
@@ -1156,21 +1136,25 @@ void QtGraphicsTreeView::doLayout()
     if (!it.isValid())
         return;
 
+    // collect unused items for reassignment
+    QHash<QtTreeModelBase::iterator_base, QtGraphicsTreeViewItem*> unused = d->items;
+    d->items.clear(); // ### FIXME: find a solution that updates in-place
+
     // position the visible items
-    const int firstVisibleIndex = index;
+    const qreal x = -horizontalOffset;
     while (y < area.height() && it.isValid()) {
-        qreal x = -horizontalOffset;
-
-        // ### FIXME: scroll the items properly
-        QtGraphicsTreeViewItem *item = 0;
-        const int i = index - firstVisibleIndex;
-        if (i >= d->items.count()) {
-            item = d->creator->create(it, index, this);
-            d->items.append(item);
-        } else {
-            item = d->creator->reassign(it, index, d->items.at(i));
+        // update item geometry
+        QtGraphicsTreeViewItem *item = unused.take(it);
+        if (!item) { // if the item did not exist
+            if (unused.isEmpty()) {
+                item = d->creator->create(it, index, this);
+            } else { // take another random item (idealy we should take from the bottom, since this kicks in early when scolling up)
+                QHash<QtTreeModelBase::iterator_base, QtGraphicsTreeViewItem*>::iterator random = unused.begin();
+                item = d->creator->reassign(it, index, random.value());
+                unused.erase(random);
+            }
         }
-
+        d->items.insert(it, item);
         QSizeF size = item->sizeHint(it, &option, Qt::PreferredSize, constraint);
         item->setGeometry(x, y, w, size.height());
         // next item
@@ -1179,9 +1163,10 @@ void QtGraphicsTreeView::doLayout()
         ++index;
     } // while
 
-    // clean up view items
-    while ((index - firstVisibleIndex) < d->items.count())
-        d->creator->recycle(d->items.takeLast());
+    // recycle any unused items left
+    QHash<QtTreeModelBase::iterator_base, QtGraphicsTreeViewItem*>::iterator it2 = unused.begin();
+    for (; it2 != unused.end(); ++it2)
+        d->creator->recycle(it2.value());
 }
 
 /*!
diff --git a/src/qgraphicstreeview.h b/src/qgraphicstreeview.h
index 6a7fdbc..3ed889c 100644
--- a/src/qgraphicstreeview.h
+++ b/src/qgraphicstreeview.h
@@ -147,8 +147,6 @@ public:
     QtGraphicsTreeViewItemCreatorBase *itemCreator() const;
     void setItemCreator(QtGraphicsTreeViewItemCreatorBase *creator);
 
-    //const QList<QtGraphicsTreeViewItem*> &visibleItems() const;
-
     virtual void doLayout();
     virtual QtTreeModelIterator itemAt(const QPointF &position, int *index = 0, QRectF *rect = 0) const;
     virtual int indexOf(const QtTreeModelIterator &it) const;
diff --git a/src/qgraphicstreeview_p.h b/src/qgraphicstreeview_p.h
index cf64ef8..dfdc3f6 100644
--- a/src/qgraphicstreeview_p.h
+++ b/src/qgraphicstreeview_p.h
@@ -142,7 +142,7 @@ public:
     void _q_mapIndexesToItems();
 #endif
 
-    void scrollItems(QtTreeModelBase::iterator_base it, QStack<QtTreeModelBase::iterator_base> stack, int index);
+    void updateItem(const QtTreeModelBase::iterator_base &it) const;
     
     QtGraphicsTreeView *q_ptr;
     QtTreeController *controller;
@@ -177,7 +177,8 @@ public:
 
     static inline qreal indentation() { return 20; } // ### hardcoded value; make styleHint
 
-    QList<QtGraphicsTreeViewItem*> items;
+    QHash<QtTreeModelBase::iterator_base, QtGraphicsTreeViewItem*> items;
+
     QtGraphicsTreeViewItemCreatorBase *creator;
     QBasicTimer layoutTimer;
 };