QDockWidget: Keep position when undocking.

Initialize undockedGeometry to roughly the current position.

Task-number: QTBUG-31044
Change-Id: I03cbe280d1215bb58ab721b60e29b45359cde76d
Reviewed-by: Andy Shaw <andy.shaw@digia.com>
(cherry picked from qtbase/0d459619a902e547d8c74745453b3bdb8f67a660)

2 files changed, 11 insertions, 0 deletions

diff --git a/src/gui/widgets/qdockwidget.cpp b/src/gui/widgets/qdockwidget.cpp
index 1ba3e9a..bb585b1 100644
--- a/src/gui/widgets/qdockwidget.cpp
+++ b/src/gui/widgets/qdockwidget.cpp
@@ -1281,6 +1281,9 @@ void QDockWidget::setFloating(bool floating)
         d->endDrag(true);
 
     QRect r = d->undockedGeometry;
+    // Keep position when undocking for the first time.
+    if (floating && isVisible() && !r.isValid())
+        r = QRect(mapToGlobal(QPoint(0, 0)), size());
 
     d->setWindowState(floating, false, floating ? r : QRect());
 
diff --git a/tests/auto/qdockwidget/tst_qdockwidget.cpp b/tests/auto/qdockwidget/tst_qdockwidget.cpp
index 22f4f23..dff0ec0 100644
--- a/tests/auto/qdockwidget/tst_qdockwidget.cpp
+++ b/tests/auto/qdockwidget/tst_qdockwidget.cpp
@@ -363,7 +363,9 @@ void tst_QDockWidget::features()
 
 void tst_QDockWidget::setFloating()
 {
+    const QRect deskRect = QApplication::desktop()->availableGeometry();
     QMainWindow mw;
+    mw.move(deskRect.left() + deskRect.width() * 2 / 3, deskRect.top() + deskRect.height() / 3);
     QDockWidget dw;
     mw.addDockWidget(Qt::LeftDockWidgetArea, &dw);
 
@@ -373,10 +375,16 @@ void tst_QDockWidget::setFloating()
 #endif
 
     QVERIFY(!dw.isFloating());
+    const QPoint dockedPosition = dw.mapToGlobal(dw.pos());
 
     QSignalSpy spy(&dw, SIGNAL(topLevelChanged(bool)));
 
     dw.setFloating(true);
+    const QPoint floatingPosition = dw.pos();
+
+    // QTBUG-31044, show approximately at old position, give or take window frame.
+    QVERIFY((dockedPosition - floatingPosition).manhattanLength() < 50);
+
     QVERIFY(dw.isFloating());
     QCOMPARE(spy.count(), 1);
     QCOMPARE(spy.at(0).value(0).toBool(), dw.isFloating());