Add expandingListItems property to QListView

This property allows to change the default behavior in
which list items occupy the entire width of the column.
Setting it to false will reduce their widths to the
minimum values, thus allowing to have intermediate free
space. Then the user will be able to begin selections
by mouse from this space.

[ChangeLog][QtWidgets][QListView] Added expandingListItems property.

Change-Id: I6bd1b147fd0335324310a165104c36f6b0d6ac9f
Task-number: QTBUG-56606
Reviewed-by: Anton Kudryavtsev <antkudr@mail.ru>
Reviewed-by: Thorbjørn Lund Martsum <tmartsum@gmail.com>

src/widgets/itemviews/qlistview.cpp

@@ -1624,6 +1624,33 @@ bool QListView::isSelectionRectVisible() const
     return d->isSelectionRectVisible();
 }
 
+/*!
+    \property QListView::expandingListItems
+    \brief if items occupy the entire width of the column
+    \since 5.9
+
+    If this property is \c true then all items in the column
+    will have the width of the column; otherwise the width of
+    each item will be determined by it's size hint.
+
+    By default, this property is \c true.
+*/
+void QListView::setExpandingListItems(bool enable)
+{
+    Q_D(QListView);
+    if (d->expandingListItems == enable)
+        return;
+    d->expandingListItems = enable;
+    if (viewMode() == ListMode && flow() == QListView::TopToBottom && isWrapping())
+        d->doDelayedItemsLayout();
+}
+
+bool QListView::isExpandingListItems() const
+{
+    Q_D(const QListView);
+    return d->expandingListItems;
+}
+
 /*!
     \reimp
 */
@@ -1650,7 +1677,8 @@ QListViewPrivate::QListViewPrivate()
       column(0),
       uniformItemSizes(false),
       batchSize(100),
-      showElasticBand(false)
+      showElasticBand(false),
+      expandingListItems(true)
 {
 }
 
@@ -2365,7 +2393,8 @@ QListViewItem QListModeViewBase::indexToListViewItem(const QModelIndex &index) c
             int right = (segment + 1 >= segmentPositions.count()
                      ? contentsSize.width()
                      : segmentPositions.at(segment + 1));
-            size.setWidth(right - pos.x());
+            size.setWidth(dd->expandingListItems ? right - pos.x()
+                                                 : qMin(size.width(), right - pos.x()));
         } else { // make the items as wide as the viewport
             size.setWidth(qMax(size.width(), viewport()->width() - 2 * spacing()));
         }
@@ -2551,8 +2580,15 @@ QVector<QModelIndex> QListModeViewBase::intersectingSet(const QRect &area) const
             if (isHidden(row))
                 continue;
             QModelIndex index = modelIndex(row);
-            if (index.isValid())
-                ret += index;
+            if (index.isValid()) {
+                if (flow() == QListView::LeftToRight || dd->expandingListItems) {
+                    ret += index;
+                } else {
+                    const int iw = indexToListViewItem(index).width(); // item width
+                    if (iw > 0 && segStartPosition - segmentPositions.at(seg) < iw)
+                        ret += index;
+                }
+            }
 #if 0 // for debugging
             else
                 qWarning("intersectingSet: row %d was invalid", row);

src/widgets/itemviews/qlistview.h

@@ -66,6 +66,7 @@ class Q_WIDGETS_EXPORT QListView : public QAbstractItemView
     Q_PROPERTY(int batchSize READ batchSize WRITE setBatchSize)
     Q_PROPERTY(bool wordWrap READ wordWrap WRITE setWordWrap)
     Q_PROPERTY(bool selectionRectVisible READ isSelectionRectVisible WRITE setSelectionRectVisible)
+    Q_PROPERTY(bool expandingListItems READ isExpandingListItems WRITE setExpandingListItems)
 
 public:
     enum Movement { Static, Free, Snap };
@@ -126,6 +127,9 @@ public:
     void setSelectionRectVisible(bool show);
     bool isSelectionRectVisible() const;
 
+    void setExpandingListItems(bool enable);
+    bool isExpandingListItems() const;
+
     QRect visualRect(const QModelIndex &index) const Q_DECL_OVERRIDE;
     void scrollTo(const QModelIndex &index, ScrollHint hint = EnsureVisible) Q_DECL_OVERRIDE;
     QModelIndex indexAt(const QPoint &p) const Q_DECL_OVERRIDE;

src/widgets/itemviews/qlistview_p.h

@@ -431,6 +431,8 @@ public:
 
     QRect elasticBand;
     bool showElasticBand;
+
+    bool expandingListItems;
 };
 
 // inline implementations

tests/auto/widgets/itemviews/qlistview/tst_qlistview.cpp

@@ -150,6 +150,7 @@ private slots:
     void horizontalScrollingByVerticalWheelEvents();
     void taskQTBUG_7232_AllowUserToControlSingleStep();
     void taskQTBUG_51086_skippingIndexesInSelectedIndexes();
+    void expandingListItems();
 };
 
 // Testing get/set functions
@@ -2486,5 +2487,28 @@ void tst_QListView::taskQTBUG_51086_skippingIndexesInSelectedIndexes()
     QVERIFY(!indexes.contains(data.index(8, 0)));
 }
 
+void tst_QListView::expandingListItems()
+{
+    auto item1 = new QStandardItem("111");
+    auto item2 = new QStandardItem("111111");
+    QStandardItemModel model;
+    model.appendRow(item1);
+    model.appendRow(item2);
+
+    QListView w;
+    w.setModel(&model);
+    w.setWrapping(true);
+    w.show();
+    QVERIFY(QTest::qWaitForWindowExposed(&w));
+
+    QVERIFY(w.visualRect(item1->index()).width() > 0);
+    QVERIFY(w.visualRect(item1->index()).width() == w.visualRect(item2->index()).width());
+
+    w.setExpandingListItems(false);
+    QApplication::processEvents();
+
+    QVERIFY(w.visualRect(item1->index()).width() < w.visualRect(item2->index()).width());
+}
+
 QTEST_MAIN(tst_QListView)
 #include "tst_qlistview.moc"