QGraphicsView - emit signal when rubber band changes.

The rubberBandRect function is nice to have, but this patch
makes it easier to track the rubber band by emiting a signal
on change.

That makes it easier (and less clumsy/hacky) to show information
related to the rubber band.

Change-Id: If65eb85d743a1804be3fdb823a821423411e9745
Reviewed-by: Andreas Aardal Hanssen <andreas@hanssen.name>
Reviewed-by: Samuel Rødal <samuel.rodal@digia.com>

dist/changes-5.1.0

@@ -86,7 +86,7 @@ QtWidgets
 ---------
 
 - QGraphicsView:
-  * Added function rubberBandRect()
+  * Added function rubberBandRect() and signal rubberBandChanged.
 
 ****************************************************************************
 *                          Database Drivers                                *

src/widgets/graphicsview/qgraphicsview.cpp

@@ -256,6 +256,20 @@ static const int QGRAPHICSVIEW_PREALLOC_STYLE_OPTIONS = 503; // largest prime <
     \sa dragMode, QGraphicsScene::setSelectionArea()
 */
 
+/*!
+    \since 5.1
+
+    \fn void QGraphicsView::rubberBandChanged(QRect rubberBandRect, QPointF fromScenePoint, QPointF toScenePoint)
+
+    This signal is emitted when the rubber band rect is changed. The viewport Rect is specified by \a rubberBandRect.
+    The drag start position and drag end position are provided in scene points with \a fromScenePoint and \a toScenePoint.
+
+    When rubberband selection ends this signal will be emitted with null vales.
+
+    \sa rubberBandRect()
+*/
+
+
 #include "qgraphicsview.h"
 #include "qgraphicsview_p.h"
 
@@ -727,16 +741,27 @@ void QGraphicsViewPrivate::updateRubberBand(const QMouseEvent *event)
     // if we didn't get the release events).
     if (!event->buttons()) {
         rubberBanding = false;
-        rubberBandRect = QRect();
+        if (!rubberBandRect.isNull()) {
+            rubberBandRect = QRect();
+            emit q->rubberBandChanged(rubberBandRect, QPointF(), QPointF());
+        }
         return;
     }
 
+    QRect oldRubberband = rubberBandRect;
+
     // Update rubberband position
     const QPoint mp = q->mapFromScene(mousePressScenePoint);
     const QPoint ep = event->pos();
     rubberBandRect = QRect(qMin(mp.x(), ep.x()), qMin(mp.y(), ep.y()),
                            qAbs(mp.x() - ep.x()) + 1, qAbs(mp.y() - ep.y()) + 1);
 
+    if (rubberBandRect != oldRubberband || lastRubberbandScenePoint != lastMouseMoveScenePoint) {
+        lastRubberbandScenePoint = lastMouseMoveScenePoint;
+        oldRubberband = rubberBandRect;
+        emit q->rubberBandChanged(rubberBandRect, mousePressScenePoint, lastRubberbandScenePoint);
+    }
+
     // Update new rubberband
     if (viewportUpdateMode != QGraphicsView::NoViewportUpdate) {
         if (viewportUpdateMode != QGraphicsView::FullViewportUpdate)
@@ -1518,7 +1543,7 @@ void QGraphicsView::setRubberBandSelectionMode(Qt::ItemSelectionMode mode)
    Notice that part of this QRect can be outise the visual viewport. It can e.g
    contain negative values.
 
-   \sa rubberBandSelectionMode
+   \sa rubberBandSelectionMode, rubberBandChanged()
 */
 
 QRect QGraphicsView::rubberBandRect() const
@@ -3316,7 +3341,10 @@ void QGraphicsView::mouseReleaseEvent(QMouseEvent *event)
                     d->updateAll();
             }
             d->rubberBanding = false;
-            d->rubberBandRect = QRect();
+            if (!d->rubberBandRect.isNull()) {
+                d->rubberBandRect = QRect();
+                emit rubberBandChanged(d->rubberBandRect, QPointF(), QPointF());
+            }
         }
     } else
 #endif

src/widgets/graphicsview/qgraphicsview.h

@@ -227,6 +227,11 @@ public Q_SLOTS:
     void invalidateScene(const QRectF &rect = QRectF(), QGraphicsScene::SceneLayers layers = QGraphicsScene::AllLayers);
     void updateSceneRect(const QRectF &rect);
 
+#ifndef QT_NO_RUBBERBAND
+Q_SIGNALS:
+    void rubberBandChanged(QRect viewportRect, QPointF fromScenePoint, QPointF toScenePoint);
+#endif
+
 protected Q_SLOTS:
     void setupViewport(QWidget *widget);
 

src/widgets/graphicsview/qgraphicsview_p.h

@@ -110,6 +110,7 @@ public:
     QPoint mousePressViewPoint;
     QPoint mousePressScreenPoint;
     QPointF lastMouseMoveScenePoint;
+    QPointF lastRubberbandScenePoint;
     QPoint lastMouseMoveScreenPoint;
     QPoint dirtyScrollOffset;
     Qt::MouseButton mousePressButton;

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

@@ -60,11 +60,12 @@ public:
 
 class MyGraphicsView : public QGraphicsView
 {
-
+    Q_OBJECT
 public:
     MyGraphicsView(QWidget *w, QLabel *l) : QGraphicsView(w), rubberbandLabel(l)
     {
         setDragMode(QGraphicsView::RubberBandDrag);
+        connect(this, SIGNAL(rubberBandChanged(QRect, QPointF, QPointF)), this, SLOT(updateRubberbandInfo(QRect, QPointF, QPointF)));
     }
 protected:
     void mouseMoveEvent(QMouseEvent *event)
@@ -80,29 +81,17 @@ 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()
+protected slots:
+    void updateRubberbandInfo(QRect r, QPointF from, QPointF to)
     {
         QString textToShow;
         QDebug s(&textToShow);
-        s << rubberBandRect();
-        if (rubberbandLabel->text() != textToShow)
-            rubberbandLabel->setText(textToShow);
+        s << r << from << to;
+        rubberbandLabel->setText(textToShow);
     }
+protected:
     QLabel *rubberbandLabel;
 };
 
@@ -135,3 +124,5 @@ int main(int argc, char *argv[])
     app.exec();
     return 0;
 }
+
+#include "rubberbandtest.moc"