Fix drawers not to be touch-draggable through modal popup shadows

Material style popups have a shadow outside the popup. QQuickOverlay
cannot block press events to children of a popup, because otherwise
interacting with popup contents would be impossible. However, since
the shadow is outside of the popup, touch events don't propagate to
the popup and get naturally blocked by the popup background. Instead,
the touch event propagates to the overlay. At this point, we must do
an additional check whether we're allowed to start dragging a drawer.

Task-number: QTBUG-60602
Change-Id: I9b5c81246bca7ea40bce0e46dc2e94558a0b9204
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

4 files changed, 163 insertions, 14 deletions

diff --git a/src/quicktemplates2/qquickoverlay.cpp b/src/quicktemplates2/qquickoverlay.cpp
index 0f7edc77..15104808 100644
--- a/src/quicktemplates2/qquickoverlay.cpp
+++ b/src/quicktemplates2/qquickoverlay.cpp
@@ -181,11 +181,23 @@ QQuickOverlayPrivate::QQuickOverlayPrivate()
 {
 }
 
-bool QQuickOverlayPrivate::startDrag(QEvent *event)
+bool QQuickOverlayPrivate::startDrag(QEvent *event, const QPointF &pos)
 {
+    Q_Q(QQuickOverlay);
     if (allDrawers.isEmpty())
         return false;
 
+    // don't start dragging a drawer if a modal popup overlay is blocking (QTBUG-60602)
+    QQuickItem *item = q->childAt(pos.x(), pos.y());
+    if (item) {
+        const auto popups = stackingOrderPopups();
+        for (QQuickPopup *popup : popups) {
+            QQuickPopupPrivate *p = QQuickPopupPrivate::get(popup);
+            if (p->dimmer == item && popup->isVisible() && popup->isModal())
+                return false;
+        }
+    }
+
     const QVector<QQuickDrawer *> drawers = stackingOrderDrawers();
     for (QQuickDrawer *drawer : drawers) {
         QQuickDrawerPrivate *p = QQuickDrawerPrivate::get(drawer);
@@ -251,7 +263,7 @@ bool QQuickOverlayPrivate::handleMouseEvent(QQuickItem *source, QMouseEvent *eve
 {
     switch (event->type()) {
     case QEvent::MouseButtonPress:
-        if (!target && startDrag(event))
+        if (!target && startDrag(event, event->windowPos()))
             return true;
         return handlePress(source, event, target);
     case QEvent::MouseMove:
@@ -269,17 +281,12 @@ bool QQuickOverlayPrivate::handleTouchEvent(QQuickItem *source, QTouchEvent *eve
     bool handled = false;
     switch (event->type()) {
     case QEvent::TouchBegin:
-        if (!target && startDrag(event))
-            handled = true;
-        else
-            handled = handlePress(source, event, target);
-        break;
-
     case QEvent::TouchUpdate:
+    case QEvent::TouchEnd:
         for (const QTouchEvent::TouchPoint &point : event->touchPoints()) {
             switch (point.state()) {
             case Qt::TouchPointPressed:
-                if (!target && startDrag(event))
+                if (!target && startDrag(event, point.scenePos()))
                     handled = true;
                 else
                     handled |= handlePress(source, event, target);
@@ -296,10 +303,6 @@ bool QQuickOverlayPrivate::handleTouchEvent(QQuickItem *source, QTouchEvent *eve
         }
         break;
 
-    case QEvent::TouchEnd:
-        handled = handleRelease(source, event, target ? target : mouseGrabberPopup.data());
-        break;
-
     default:
         break;
     }
diff --git a/src/quicktemplates2/qquickoverlay_p_p.h b/src/quicktemplates2/qquickoverlay_p_p.h
index fa53d52b..5553bda8 100644
--- a/src/quicktemplates2/qquickoverlay_p_p.h
+++ b/src/quicktemplates2/qquickoverlay_p_p.h
@@ -70,7 +70,7 @@ public:
         return overlay->d_func();
     }
 
-    bool startDrag(QEvent *event);
+    bool startDrag(QEvent *event, const QPointF &pos);
     bool handlePress(QQuickItem *source, QEvent *event, QQuickPopup *target);
     bool handleMove(QQuickItem *source, QEvent *event, QQuickPopup *target);
     bool handleRelease(QQuickItem *source, QEvent *event, QQuickPopup *target);
diff --git a/tests/auto/drawer/data/dragOverModalShadow.qml b/tests/auto/drawer/data/dragOverModalShadow.qml
new file mode 100644
index 00000000..66eb2f4b
--- /dev/null
+++ b/tests/auto/drawer/data/dragOverModalShadow.qml
@@ -0,0 +1,87 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, 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 The Qt Company Ltd 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."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+import QtQuick 2.6
+import QtQuick.Controls 2.0
+
+ApplicationWindow {
+    width: 400
+    height: 400
+
+    property alias drawer: drawer
+    property alias popup: popup
+
+    Drawer {
+        id: drawer
+        width: 200
+        height: parent.height
+        dragMargin: parent.width
+    }
+
+    Popup {
+        id: popup
+        modal: true
+        x: (parent.width - width) / 2
+        y: (parent.height - height) / 2
+        width: parent.width / 2
+        height: parent.height / 2
+
+        Rectangle {
+            objectName: "shadow"
+            parent: popup.background
+            anchors.fill: parent
+            anchors.margins: -20
+
+            z: -1
+            opacity: 0.5
+            color: "silver"
+        }
+    }
+}
diff --git a/tests/auto/drawer/tst_drawer.cpp b/tests/auto/drawer/tst_drawer.cpp
index 6f3e1d64..9c30f8cf 100644
--- a/tests/auto/drawer/tst_drawer.cpp
+++ b/tests/auto/drawer/tst_drawer.cpp
@@ -94,6 +94,9 @@ private slots:
     void flickable_data();
     void flickable();
 
+    void dragOverModalShadow_data();
+    void dragOverModalShadow();
+
 private:
     struct TouchDeviceDeleter
     {
@@ -962,6 +965,62 @@ void tst_Drawer::flickable()
     QVERIFY(!flickable->isDragging());
 }
 
+void tst_Drawer::dragOverModalShadow_data()
+{
+    QTest::addColumn<bool>("mouse");
+    QTest::newRow("mouse") << true;
+    QTest::newRow("touch") << false;
+}
+
+// QTBUG-60602
+void tst_Drawer::dragOverModalShadow()
+{
+    QFETCH(bool, mouse);
+
+    QQuickApplicationHelper helper(this, QStringLiteral("dragOverModalShadow.qml"));
+    QQuickWindow *window = helper.window;
+    window->show();
+    QVERIFY(QTest::qWaitForWindowActive(window));
+
+    QQuickDrawer *drawer = window->property("drawer").value<QQuickDrawer *>();
+    QVERIFY(drawer);
+
+    QQuickPopup *popup = window->property("popup").value<QQuickPopup *>();
+    QVERIFY(popup);
+
+    popup->open();
+    QVERIFY(popup->isVisible());
+    QVERIFY(!drawer->isVisible());
+
+    const QPoint from(popup->x(), popup->y() + popup->height() + 5);
+    const QPoint to(popup->x() + popup->width(), popup->y() + popup->height() + 5);
+
+    if (mouse)
+        QTest::mousePress(window, Qt::LeftButton, Qt::NoModifier, from);
+    else
+        QTest::touchEvent(window, touchDevice.data()).press(0, from);
+    QVERIFY(!drawer->isVisible());
+
+    static const int steps = 10;
+    for (int i = 0; i < steps; ++i) {
+        int x = from.x() + i * qAbs(from.x() - to.x()) / steps;
+        int y = from.y() + i * qAbs(from.y() - to.y()) / steps;
+
+        if (mouse)
+            QTest::mouseMove(window, QPoint(x, y));
+        else
+            QTest::touchEvent(window, touchDevice.data()).move(0, QPoint(x, y));
+        QTest::qWait(1); // avoid infinite velocity
+        QVERIFY(!drawer->isVisible());
+    }
+
+    if (mouse)
+        QTest::mouseRelease(window, Qt::LeftButton, Qt::NoModifier, to);
+    else
+        QTest::touchEvent(window, touchDevice.data()).release(0, to);
+    QVERIFY(!drawer->isVisible());
+}
+
 QTEST_MAIN(tst_Drawer)
 
 #include "tst_drawer.moc"