Extend selections in QGraphicsView when selection extension key down

If the user has some objects selected and holds down the "extend selection"
key (Control on Windows, Command on Mac OS X), clicking and dragging a
rubber band selection deselects the current selection.  This is
counter-intuitive and confusing for users.

This commit fixes the behavior so users can extend selections using the
rubber band when the proper key is held down.

Task-number: QTBUG-6523
Change-Id: Ieda4aaa50adb351c0405f5cb8aae23332eec58a9
Reviewed-by: Andreas Aardal Hanssen <andreas@hanssen.name>

1 files changed, 34 insertions, 4 deletions

diff --git a/src/widgets/graphicsview/qgraphicsscene.cpp b/src/widgets/graphicsview/qgraphicsscene.cpp
index 8765b8114d..aa42445b2a 100644
--- a/src/widgets/graphicsview/qgraphicsscene.cpp
+++ b/src/widgets/graphicsview/qgraphicsscene.cpp
@@ -1468,6 +1468,8 @@ void QGraphicsScenePrivate::mousePressEventHandler(QGraphicsSceneMouseEvent *mou
 
         QGraphicsView *view = mouseEvent->widget() ? qobject_cast<QGraphicsView *>(mouseEvent->widget()->parentWidget()) : 0;
         bool dontClearSelection = view && view->dragMode() == QGraphicsView::ScrollHandDrag;
+        bool extendSelection = (mouseEvent->modifiers() & Qt::ControlModifier) != 0;
+        dontClearSelection |= extendSelection;
         if (!dontClearSelection) {
             // Clear the selection if the originating view isn't in scroll
             // hand drag mode. The view will clear the selection if no drag
@@ -2263,6 +2265,28 @@ void QGraphicsScene::setSelectionArea(const QPainterPath &path, const QTransform
 void QGraphicsScene::setSelectionArea(const QPainterPath &path, Qt::ItemSelectionMode mode,
                                       const QTransform &deviceTransform)
 {
+    setSelectionArea(path, Qt::ReplaceSelection, mode, deviceTransform);
+}
+
+/*!
+    \overload
+    \since 5.5
+
+    Sets the selection area to \a path using \a mode to determine if items are
+    included in the selection area.
+
+    \a deviceTransform is the transformation that applies to the view, and needs to
+    be provided if the scene contains items that ignore transformations.
+
+    \a selectionOperation determines what to do with the currently selected items.
+
+    \sa clearSelection(), selectionArea()
+*/
+void QGraphicsScene::setSelectionArea(const QPainterPath &path,
+                                      Qt::ItemSelectionOperation selectionOperation,
+                                      Qt::ItemSelectionMode mode,
+                                      const QTransform &deviceTransform)
+{
     Q_D(QGraphicsScene);
 
     // Note: with boolean path operations, we can improve performance here
@@ -2287,10 +2311,16 @@ void QGraphicsScene::setSelectionArea(const QPainterPath &path, Qt::ItemSelectio
         }
     }
 
-    // Unselect all items outside path.
-    foreach (QGraphicsItem *item, unselectItems) {
-        item->setSelected(false);
-        changed = true;
+    switch (selectionOperation) {
+    case Qt::ReplaceSelection:
+        // Deselect all items outside path.
+        foreach (QGraphicsItem *item, unselectItems) {
+            item->setSelected(false);
+            changed = true;
+        }
+        break;
+    default:
+        break;
     }
 
     // Reenable emitting selectionChanged() for individual items.