QGraphicsView - add function to get RubberBand rect

In many situations it is handy to know the rubberband rect.
There are many situations where we want to show something
related to the rubberband.

Regardless how that is done the rubberband area is needed.
(Not having this is a flaw that can force people to do make
a customized rubberband just to get this information)

Change-Id: Ia854db4c0022b6a97b150af2b4bb78fd5e974991
Reviewed-by: Andreas Aardal Hanssen <andreas@hanssen.name>
Reviewed-by: Samuel Rødal <samuel.rodal@digia.com>

dist/changes-5.1.0

@@ -82,7 +82,11 @@ QtNetwork
 
  -
 
+QtWidgets
+---------
 
+- QGraphicsView:
+  * Added function rubberBandRect()
 
 ****************************************************************************
 *                          Database Drivers                                *

src/widgets/graphicsview/qgraphicsview.cpp

@@ -1496,7 +1496,7 @@ void QGraphicsView::setDragMode(DragMode mode)
     The default value is Qt::IntersectsItemShape; all items whose shape
     intersects with or is contained by the rubber band are selected.
 
-    \sa dragMode, items()
+    \sa dragMode, items(), rubberBandRect()
 */
 Qt::ItemSelectionMode QGraphicsView::rubberBandSelectionMode() const
 {
@@ -1508,6 +1508,27 @@ void QGraphicsView::setRubberBandSelectionMode(Qt::ItemSelectionMode mode)
     Q_D(QGraphicsView);
     d->rubberBandSelectionMode = mode;
 }
+
+/*!
+   \since 5.1
+   This functions returns the current rubber band area (in viewport coordinates) if the user
+   is currently doing an itemselection with rubber band. When the user is not using the
+   rubber band this functions returns (a null) QRectF().
+
+   Notice that part of this QRect can be outise the visual viewport. It can e.g
+   contain negative values.
+
+   \sa rubberBandSelectionMode
+*/
+
+QRect QGraphicsView::rubberBandRect() const
+{
+    Q_D(const QGraphicsView);
+    if (d->dragMode != QGraphicsView::RubberBandDrag || !d->sceneInteractionAllowed || !d->rubberBanding)
+        return QRect();
+
+    return d->rubberBandRect;
+}
 #endif
 
 /*!

src/widgets/graphicsview/qgraphicsview.h

@@ -146,6 +146,7 @@ public:
 #ifndef QT_NO_RUBBERBAND
     Qt::ItemSelectionMode rubberBandSelectionMode() const;
     void setRubberBandSelectionMode(Qt::ItemSelectionMode mode);
+    QRect rubberBandRect() const;
 #endif
 
     CacheMode cacheMode() const;

tests/manual/widgets/qgraphicsview/rubberband/rubberbandtest.cpp

@@ -62,7 +62,7 @@ class MyGraphicsView : public QGraphicsView
 {
 
 public:
-    MyGraphicsView() : QGraphicsView()
+    MyGraphicsView(QWidget *w, QLabel *l) : QGraphicsView(w), rubberbandLabel(l)
     {
         setDragMode(QGraphicsView::RubberBandDrag);
     }
@@ -80,13 +80,43 @@ protected:
         int yglobal = event->globalY();
         if (yglobal > bottomPos)
             verticalScrollBar()->setValue(verticalScrollBar()->value() + 10);
+        updateRubberbandInfo();
     }
+
+    void mouseReleaseEvent(QMouseEvent *event)
+    {
+        QGraphicsView::mouseReleaseEvent(event);
+        updateRubberbandInfo();
+    }
+
+    void wheelEvent (QWheelEvent *event)
+    {
+        QGraphicsView::wheelEvent(event);
+        updateRubberbandInfo();
+    }
+
+    void updateRubberbandInfo()
+    {
+        QString textToShow;
+        QDebug s(&textToShow);
+        s << rubberBandRect();
+        if (rubberbandLabel->text() != textToShow)
+            rubberbandLabel->setText(textToShow);
+    }
+    QLabel *rubberbandLabel;
 };
 
 int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);
-    MyGraphicsView v;
+
+    QWidget w;
+    w.setLayout(new QVBoxLayout);
+    QLabel *l = new QLabel(&w);
+    MyGraphicsView &v = *(new MyGraphicsView(&w, l));
+
+    w.layout()->addWidget(&v);
+    w.layout()->addWidget(l);
 
     QGraphicsScene s(0.0, 0.0, 5000.0, 5000.0);
     v.setScene(&s);
@@ -100,7 +130,8 @@ int main(int argc, char *argv[])
             item->setRect(QRectF(v * 80.0, u * 80.0, 50.0, 20.0));
             s.addItem(item);
         }
-    v.show();
+
+    w.show();
     app.exec();
     return 0;
 }