Allow MouseArea dragging to filter mouse events from descendants

This allows dragging a MouseArea that contains a clickable MouseArea,
for example.

Task-number: QTBUG-12323
Reviewed-by: Michael Brasser

6 files changed, 189 insertions, 6 deletions

diff --git a/doc/src/snippets/declarative/mouseareadragfilter.qml b/doc/src/snippets/declarative/mouseareadragfilter.qml
new file mode 100644
index 0000000..52ed10c
--- /dev/null
+++ b/doc/src/snippets/declarative/mouseareadragfilter.qml
@@ -0,0 +1,72 @@
+/****************************************************************************
+**
+** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the QtDeclarative module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** You may use this file under the terms of the BSD license as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of Nokia Corporation and its Subsidiary(-ies) nor
+**     the names of its contributors may be used to endorse or promote
+**     products derived from this software without specific prior written
+**     permission.
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+//! [dragfilter]
+import Qt 4.7
+
+Rectangle {
+    width: 480
+    height: 320
+    Rectangle {
+        x: 30; y: 30
+        width: 300; height: 240
+        color: "lightsteelblue"
+
+        MouseArea {
+            anchors.fill: parent
+            drag.target: parent;
+            drag.axis: "XAxis"
+            drag.minimumX: 30
+            drag.maximumX: 150
+            drag.filterChildren: true
+
+            Rectangle {
+                color: "yellow"
+                x: 50; y : 50
+                width: 100; height: 100
+                MouseArea {
+                    anchors.fill: parent
+                    onClicked: console.log("Clicked")
+                }
+            }
+        }
+    }
+}
+//! [dragfilter]
diff --git a/src/declarative/graphicsitems/qdeclarativeflickable.cpp b/src/declarative/graphicsitems/qdeclarativeflickable.cpp
index 9af5f56..b286e11 100644
--- a/src/declarative/graphicsitems/qdeclarativeflickable.cpp
+++ b/src/declarative/graphicsitems/qdeclarativeflickable.cpp
@@ -1214,6 +1214,7 @@ bool QDeclarativeFlickable::sendMouseEvent(QGraphicsSceneMouseEvent *event)
 
             d->handleMousePressEvent(&mouseEvent);
             d->captureDelayedPress(event);
+            stealThisEvent = d->stealMouse;   // Update stealThisEvent in case changed by function call above
             break;
         case QEvent::GraphicsSceneMouseRelease:
             if (d->delayedPressEvent) {
@@ -1234,7 +1235,6 @@ bool QDeclarativeFlickable::sendMouseEvent(QGraphicsSceneMouseEvent *event)
         default:
             break;
         }
-        stealThisEvent = d->stealMouse;   // Update stealThisEvent and grabber in case changed by function calls above
         grabber = qobject_cast<QDeclarativeItem*>(s->mouseGrabberItem());
         if (grabber && stealThisEvent && !grabber->keepMouseGrab() && grabber != this) {
             d->clearDelayedPress();
diff --git a/src/declarative/graphicsitems/qdeclarativemousearea.cpp b/src/declarative/graphicsitems/qdeclarativemousearea.cpp
index 8ee6093..40c621a 100644
--- a/src/declarative/graphicsitems/qdeclarativemousearea.cpp
+++ b/src/declarative/graphicsitems/qdeclarativemousearea.cpp
@@ -53,7 +53,7 @@ static const int PressAndHoldDelay = 800;
 
 QDeclarativeDrag::QDeclarativeDrag(QObject *parent)
 : QObject(parent), _target(0), _axis(XandYAxis), _xmin(-FLT_MAX), _xmax(FLT_MAX), _ymin(-FLT_MAX), _ymax(FLT_MAX),
-_active(false)
+_active(false), _filterChildren(false)
 {
 }
 
@@ -160,12 +160,24 @@ void QDeclarativeDrag::setActive(bool drag)
     emit activeChanged();
 }
 
+bool QDeclarativeDrag::filterChildren() const
+{
+    return _filterChildren;
+}
+
+void QDeclarativeDrag::setFilterChildren(bool filter)
+{
+    if (_filterChildren == filter)
+        return;
+    _filterChildren = filter;
+    emit filterChildrenChanged();
+}
+
 QDeclarativeMouseAreaPrivate::~QDeclarativeMouseAreaPrivate()
 {
     delete drag;
 }
 
-
 /*!
     \qmlclass MouseArea QDeclarativeMouseArea
     \since 4.7
@@ -398,6 +410,7 @@ void QDeclarativeMouseArea::mousePressEvent(QGraphicsSceneMouseEvent *event)
 {
     Q_D(QDeclarativeMouseArea);
     d->moved = false;
+    d->stealMouse = false;
     if (!d->absorb)
         QDeclarativeItem::mousePressEvent(event);
     else {
@@ -456,8 +469,10 @@ void QDeclarativeMouseArea::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
         const int dragThreshold = QApplication::startDragDistance();
         qreal dx = qAbs(curLocalPos.x() - startLocalPos.x());
         qreal dy = qAbs(curLocalPos.y() - startLocalPos.y());
-        if ((d->dragX && !(dx < dragThreshold)) || (d->dragY && !(dy < dragThreshold)))
+        if ((d->dragX && !(dx < dragThreshold)) || (d->dragY && !(dy < dragThreshold))) {
             d->drag->setActive(true);
+            d->stealMouse = true;
+        }
         if (!keepMouseGrab()) {
             if ((!d->dragY && dy < dragThreshold && d->dragX && dx > dragThreshold)
                 || (!d->dragX && dx < dragThreshold && d->dragY && dy > dragThreshold)
@@ -495,6 +510,7 @@ void QDeclarativeMouseArea::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
 void QDeclarativeMouseArea::mouseReleaseEvent(QGraphicsSceneMouseEvent *event)
 {
     Q_D(QDeclarativeMouseArea);
+    d->stealMouse = false;
     if (!d->absorb) {
         QDeclarativeItem::mouseReleaseEvent(event);
     } else {
@@ -505,6 +521,8 @@ void QDeclarativeMouseArea::mouseReleaseEvent(QGraphicsSceneMouseEvent *event)
         // If we don't accept hover, we need to reset containsMouse.
         if (!acceptHoverEvents())
             setHovered(false);
+        if (scene()->mouseGrabberItem() == this)
+            ungrabMouse();
         setKeepMouseGrab(false);
     }
 }
@@ -579,6 +597,71 @@ bool QDeclarativeMouseArea::sceneEvent(QEvent *event)
     return rv;
 }
 
+bool QDeclarativeMouseArea::sendMouseEvent(QGraphicsSceneMouseEvent *event)
+{
+    Q_D(QDeclarativeMouseArea);
+    QGraphicsSceneMouseEvent mouseEvent(event->type());
+    QRectF myRect = mapToScene(QRectF(0, 0, width(), height())).boundingRect();
+
+    QGraphicsScene *s = scene();
+    QDeclarativeItem *grabber = s ? qobject_cast<QDeclarativeItem*>(s->mouseGrabberItem()) : 0;
+    bool stealThisEvent = d->stealMouse;
+    if ((stealThisEvent || myRect.contains(event->scenePos().toPoint())) && (!grabber || !grabber->keepMouseGrab())) {
+        mouseEvent.setAccepted(false);
+        for (int i = 0x1; i <= 0x10; i <<= 1) {
+            if (event->buttons() & i) {
+                Qt::MouseButton button = Qt::MouseButton(i);
+                mouseEvent.setButtonDownPos(button, mapFromScene(event->buttonDownPos(button)));
+            }
+        }
+        mouseEvent.setScenePos(event->scenePos());
+        mouseEvent.setLastScenePos(event->lastScenePos());
+        mouseEvent.setPos(mapFromScene(event->scenePos()));
+        mouseEvent.setLastPos(mapFromScene(event->lastScenePos()));
+
+        switch(mouseEvent.type()) {
+        case QEvent::GraphicsSceneMouseMove:
+            mouseMoveEvent(&mouseEvent);
+            break;
+        case QEvent::GraphicsSceneMousePress:
+            mousePressEvent(&mouseEvent);
+            break;
+        case QEvent::GraphicsSceneMouseRelease:
+            mouseReleaseEvent(&mouseEvent);
+            break;
+        default:
+            break;
+        }
+        grabber = qobject_cast<QDeclarativeItem*>(s->mouseGrabberItem());
+        if (grabber && stealThisEvent && !grabber->keepMouseGrab() && grabber != this)
+            grabMouse();
+
+        return stealThisEvent;
+    }
+    if (mouseEvent.type() == QEvent::GraphicsSceneMouseRelease) {
+        d->stealMouse = false;
+        ungrabMouse();
+    }
+    return false;
+}
+
+bool QDeclarativeMouseArea::sceneEventFilter(QGraphicsItem *i, QEvent *e)
+{
+    Q_D(QDeclarativeMouseArea);
+    if (!d->absorb || !isVisible() || !d->drag || !d->drag->filterChildren())
+        return QDeclarativeItem::sceneEventFilter(i, e);
+    switch (e->type()) {
+    case QEvent::GraphicsSceneMousePress:
+    case QEvent::GraphicsSceneMouseMove:
+    case QEvent::GraphicsSceneMouseRelease:
+        return sendMouseEvent(static_cast<QGraphicsSceneMouseEvent *>(e));
+    default:
+        break;
+    }
+
+    return QDeclarativeItem::sceneEventFilter(i, e);
+}
+
 void QDeclarativeMouseArea::timerEvent(QTimerEvent *event)
 {
     Q_D(QDeclarativeMouseArea);
@@ -759,6 +842,7 @@ QDeclarativeDrag *QDeclarativeMouseArea::drag()
     \qmlproperty real MouseArea::drag.maximumX
     \qmlproperty real MouseArea::drag.minimumY
     \qmlproperty real MouseArea::drag.maximumY
+    \qmlproperty bool MouseArea::drag.filterChildren
 
     \c drag provides a convenient way to make an item draggable.
 
@@ -779,6 +863,12 @@ QDeclarativeDrag *QDeclarativeMouseArea::drag()
     for \c rect in the above example, it cannot be dragged along the X-axis.
     This can be avoided by settng the anchor value to \c undefined in 
     an \l onPressed handler.
+
+    If \c drag.filterChildren is set to true, a drag can override descendant MouseAreas.  This
+    enables a parent MouseArea to handle drags, for example, while descendants handle clicks:
+
+    \snippet doc/src/snippets/declarative/mouseareadragfilter.qml dragfilter
+
 */
 
 QT_END_NAMESPACE
diff --git a/src/declarative/graphicsitems/qdeclarativemousearea_p.h b/src/declarative/graphicsitems/qdeclarativemousearea_p.h
index 4fe3fcb..0da7515 100644
--- a/src/declarative/graphicsitems/qdeclarativemousearea_p.h
+++ b/src/declarative/graphicsitems/qdeclarativemousearea_p.h
@@ -62,6 +62,7 @@ class Q_AUTOTEST_EXPORT QDeclarativeDrag : public QObject
     Q_PROPERTY(qreal minimumY READ ymin WRITE setYmin NOTIFY minimumYChanged)
     Q_PROPERTY(qreal maximumY READ ymax WRITE setYmax NOTIFY maximumYChanged)
     Q_PROPERTY(bool active READ active NOTIFY activeChanged)
+    Q_PROPERTY(bool filterChildren READ filterChildren WRITE setFilterChildren NOTIFY filterChildrenChanged)
     //### consider drag and drop
 
 public:
@@ -88,6 +89,9 @@ public:
     bool active() const;
     void setActive(bool);
 
+    bool filterChildren() const;
+    void setFilterChildren(bool);
+
 Q_SIGNALS:
     void targetChanged();
     void axisChanged();
@@ -96,6 +100,7 @@ Q_SIGNALS:
     void minimumYChanged();
     void maximumYChanged();
     void activeChanged();
+    void filterChildrenChanged();
 
 private:
     QGraphicsObject *_target;
@@ -104,7 +109,8 @@ private:
     qreal _xmax;
     qreal _ymin;
     qreal _ymax;
-    bool _active;
+    bool _active : 1;
+    bool _filterChildren: 1;
     Q_DISABLE_COPY(QDeclarativeDrag)
 };
 
@@ -177,6 +183,8 @@ protected:
     void hoverMoveEvent(QGraphicsSceneHoverEvent *event);
     void hoverLeaveEvent(QGraphicsSceneHoverEvent *event);
     bool sceneEvent(QEvent *);
+    bool sendMouseEvent(QGraphicsSceneMouseEvent *event);
+    bool sceneEventFilter(QGraphicsItem *i, QEvent *e);
     void timerEvent(QTimerEvent *event);
 
     virtual void geometryChanged(const QRectF &newGeometry,
diff --git a/src/declarative/graphicsitems/qdeclarativemousearea_p_p.h b/src/declarative/graphicsitems/qdeclarativemousearea_p_p.h
index 3d7bd1e..cf9dc18 100644
--- a/src/declarative/graphicsitems/qdeclarativemousearea_p_p.h
+++ b/src/declarative/graphicsitems/qdeclarativemousearea_p_p.h
@@ -68,7 +68,7 @@ class QDeclarativeMouseAreaPrivate : public QDeclarativeItemPrivate
 public:
     QDeclarativeMouseAreaPrivate()
       : absorb(true), hovered(false), pressed(false), longPress(false),
-      moved(false), drag(0)
+      moved(false), stealMouse(false), drag(0)
     {
     }
 
@@ -78,6 +78,7 @@ public:
     {
         Q_Q(QDeclarativeMouseArea);
         q->setAcceptedMouseButtons(Qt::LeftButton);
+        q->setFiltersChildEvents(true);
     }
 
     void saveEvent(QGraphicsSceneMouseEvent *event) {
@@ -101,6 +102,7 @@ public:
     bool moved : 1;
     bool dragX : 1;
     bool dragY : 1;
+    bool stealMouse : 1;
     QDeclarativeDrag *drag;
     QPointF startScene;
     qreal startX;
diff --git a/tests/auto/declarative/qdeclarativemousearea/tst_qdeclarativemousearea.cpp b/tests/auto/declarative/qdeclarativemousearea/tst_qdeclarativemousearea.cpp
index 5a10372..c9bb467 100644
--- a/tests/auto/declarative/qdeclarativemousearea/tst_qdeclarativemousearea.cpp
+++ b/tests/auto/declarative/qdeclarativemousearea/tst_qdeclarativemousearea.cpp
@@ -137,6 +137,17 @@ void tst_QDeclarativeMouseArea::dragProperties()
     QCOMPARE(yminSpy.count(),1);
     QCOMPARE(ymaxSpy.count(),1);
 
+    // filterChildren
+    QSignalSpy filterChildrenSpy(drag, SIGNAL(filterChildrenChanged()));
+
+    drag->setFilterChildren(true);
+
+    QVERIFY(drag->filterChildren());
+    QCOMPARE(filterChildrenSpy.count(), 1);
+
+    drag->setFilterChildren(true);
+    QCOMPARE(filterChildrenSpy.count(), 1);
+
     delete canvas;
 }