QAbstractItemView: use only a 1x1 QRect for selecting on mouse press

Before commit f1e90768095be37419ba4bf3c69ec5c860bdbcb6, mousePressEvent
called the virtual method setSelection(const QRect&, SelectionFlags)
with the 1x1 rectangle which contains only the clicked QPoint, unless
the SelectionFlag "Current" was set because Shift was pressed during
the mouse press.

Since that commit, the behavior has been changed such that the
rectangle is the one that is spanned by the center of the clicked item
and the clicked pixel. In theory, the result should be the same (i.e.,
only the clicked item should be selected), but

* the code path in QListView::setSelection for 1x1 QRects is more
  efficient, and
* using a larger QRect can cause problems with custom views, see the
  comments in QTBUG-18009

This commit ensures that the 1x1 QRect is used again, unless the
SelectionFlag "Current" is used.

Change-Id: I70dd70c083c20a3af6cd6095aa89a489756b505f
Task-number: QTBUG-18009
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>
Reviewed-by: Thorbjørn Lund Martsum <tmartsum@gmail.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/src/widgets/itemviews/qabstractitemview.cpp b/src/widgets/itemviews/qabstractitemview.cpp
index d36431c716..4dd8ad0215 100644
--- a/src/widgets/itemviews/qabstractitemview.cpp
+++ b/src/widgets/itemviews/qabstractitemview.cpp
@@ -1735,13 +1735,18 @@ void QAbstractItemView::mousePressEvent(QMouseEvent *event)
         d->autoScroll = false;
         d->selectionModel->setCurrentIndex(index, QItemSelectionModel::NoUpdate);
         d->autoScroll = autoScroll;
-        QRect rect(visualRect(d->currentSelectionStartIndex).center(), pos);
         if (command.testFlag(QItemSelectionModel::Toggle)) {
             command &= ~QItemSelectionModel::Toggle;
             d->ctrlDragSelectionFlag = d->selectionModel->isSelected(index) ? QItemSelectionModel::Deselect : QItemSelectionModel::Select;
             command |= d->ctrlDragSelectionFlag;
         }
-        setSelection(rect, command);
+
+        if ((command & QItemSelectionModel::Current) == 0) {
+            setSelection(QRect(pos, QSize(1, 1)), command);
+        } else {
+            QRect rect(visualRect(d->currentSelectionStartIndex).center(), pos);
+            setSelection(rect, command);
+        }
 
         // signal handlers may change the model
         emit pressed(index);