From 4f95e66f940c3a6c72f51c2428620c09e30bbd0b Mon Sep 17 00:00:00 2001 From: Volker Hilsheimer Date: Wed, 20 Dec 2023 16:51:41 +0100 Subject: QWidget: deliver DragLeave events symmetrically MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit If a widget received a DragEnter event that it didn't accept, then the UnderMouse widget attribute gets set. But the drag manager never got a drag target, so the DragLeave event was never delivered, leaving the UnderMouse attribute set incorrectly. We always need to send DragLeave events to the receiver, even if the DragEnter or DragMove was not accepted. Otherwise we are not in balance, and the UnderMouse attribute will remain set. This is a change of behavior and a very old bug, so only fixing this in unreleased branches. Test case added to verify that explicitly generated drag events result in the correct enter/leave events. [ChangeLog][QtWidgets][QWidget] DragLeave events are now always sent to the widget the mouse is leaving, even if it didn't accept the DragEnter event. Fixes: QTBUG-50403 Pick-to: 6.7 Change-Id: I5eae49da000fb4fea81f1767f0e73a06a6b78975 Reviewed-by: Tor Arne Vestbø Reviewed-by: Christian Ehrlicher Reviewed-by: Axel Spoerl --- src/widgets/kernel/qapplication.cpp | 12 ++- tests/auto/widgets/kernel/qwidget/tst_qwidget.cpp | 96 +++++++++++++++++++++++ 2 files changed, 106 insertions(+), 2 deletions(-) diff --git a/src/widgets/kernel/qapplication.cpp b/src/widgets/kernel/qapplication.cpp index 163fb7beff..a17c6934fa 100644 --- a/src/widgets/kernel/qapplication.cpp +++ b/src/widgets/kernel/qapplication.cpp @@ -3039,8 +3039,16 @@ bool QApplication::notify(QObject *receiver, QEvent *e) #endif w = qobject_cast(QDragManager::self()->currentTarget()); - if (!w) - break; + if (!w) { + // The widget that received DragEnter didn't accept the event, so we have no + // current drag target in the QDragManager. But DragLeave still needs to be + // dispatched so that enter/leave events are in balance (and so that UnderMouse + // gets cleared). + if (e->type() == QEvent::DragLeave) + w = static_cast(receiver); + else + break; + } if (e->type() == QEvent::DragMove || e->type() == QEvent::Drop) { QDropEvent *dragEvent = static_cast(e); QWidget *origReceiver = static_cast(receiver); diff --git a/tests/auto/widgets/kernel/qwidget/tst_qwidget.cpp b/tests/auto/widgets/kernel/qwidget/tst_qwidget.cpp index 386c7c5503..a5e3201f01 100644 --- a/tests/auto/widgets/kernel/qwidget/tst_qwidget.cpp +++ b/tests/auto/widgets/kernel/qwidget/tst_qwidget.cpp @@ -13,6 +13,7 @@ #include #include #include +#include #include #include #include @@ -37,6 +38,7 @@ #include #include #include +#include #include #include #include @@ -435,6 +437,8 @@ private slots: void setVisibleDuringDestruction(); + void dragEnterLeaveSymmetry(); + private: const QString m_platform; QSize m_testWidgetSize; @@ -13441,5 +13445,97 @@ void tst_QWidget::setVisibleDuringDestruction() QTRY_COMPARE(signalSpy.count(), 4); } +/*! + Verify that we deliver DragEnter/Leave events symmetrically, even if the + widget entered didn't accept the DragEnter event. +*/ +void tst_QWidget::dragEnterLeaveSymmetry() +{ + QWidget widget; + widget.setAcceptDrops(true); + QLineEdit lineEdit; + QLabel label("Hello world"); + label.setAcceptDrops(true); + + struct EventFilter : QObject + { + bool eventFilter(QObject *receiver, QEvent *event) override + { + switch (event->type()) { + case QEvent::DragEnter: + case QEvent::DragLeave: + receivers[event->type()] << receiver; + break; + + default: + break; + } + + return false; + } + + QMap> receivers; + + void clear() { receivers.clear(); } + bool hasEntered(QWidget *widget) const + { + return receivers.value(QEvent::DragEnter).contains(widget); + } + bool hasLeft(QWidget *widget) const + { + return receivers.value(QEvent::DragLeave).contains(widget); + } + } filter; + + widget.installEventFilter(&filter); + lineEdit.installEventFilter(&filter); + label.installEventFilter(&filter); + + QVBoxLayout vbox; + vbox.setContentsMargins(10, 10, 10, 10); + vbox.addWidget(&lineEdit); + vbox.addWidget(&label); + widget.setLayout(&vbox); + + widget.show(); + QVERIFY(QTest::qWaitForWindowExposed(&widget)); + + QMimeData data; + data.setColorData(QVariant::fromValue(Qt::red)); + QWindowSystemInterface::handleDrag(widget.windowHandle(), &data, QPoint(1, 1), + Qt::ActionMask, Qt::LeftButton, {}); + QVERIFY(filter.hasEntered(&widget)); + QVERIFY(!filter.hasEntered(&lineEdit)); + QVERIFY(!filter.hasEntered(&label)); + QVERIFY(widget.underMouse()); + QVERIFY(!lineEdit.underMouse()); + filter.clear(); + + QWindowSystemInterface::handleDrag(widget.windowHandle(), &data, lineEdit.geometry().center(), + Qt::ActionMask, Qt::LeftButton, {}); + // DragEnter propagates as the lineEdit doesn't want it, so the widget + // sees both a Leave and an Enter event + QVERIFY(filter.hasLeft(&widget)); + QVERIFY(filter.hasEntered(&widget)); + QVERIFY(filter.hasEntered(&widget)); + // both have the UnderMouse attribute set + QVERIFY(lineEdit.underMouse()); + QVERIFY(widget.underMouse()); + + // The lineEdit didn't accept the DragEnter, but it should still has to + // get the DragLeave so that UnderMouse is cleared; the widget gets both + // Leave and Enter through propagation. + QWindowSystemInterface::handleDrag(widget.windowHandle(), &data, label.geometry().center(), + Qt::ActionMask, Qt::LeftButton, {}); + QVERIFY(filter.hasLeft(&lineEdit)); + QVERIFY(filter.hasLeft(&widget)); + QVERIFY(filter.hasEntered(&label)); + QVERIFY(filter.hasEntered(&widget)); + + QVERIFY(!lineEdit.underMouse()); + QVERIFY(label.underMouse()); + QVERIFY(widget.underMouse()); +} + QTEST_MAIN(tst_QWidget) #include "tst_qwidget.moc" -- cgit v1.2.3