QWidget: close the QWindow in QWidget::close

We want to close the window, end full screen mode on macOS, and free
platform resources. This is all done by QWindow::close. QWindow::close
closes the platform window, triggering a closeEvent to QWidgetWindow,
which then calls QWidgetPrivate::close_helper.

This way, closing a window via QWidget::close, QWindow::close, or
interactively by the user are all equivalent.

The QCloseEvent generated by the widget needs to be spontaneous for
window-system generated events (i.e. the user clicked the close button),
and non-spontaneous if the window closes because of a call to
QWindow::close. To keep track of whether the event originated in an
explicit call to QWindow::close, add a boolean to the QWindowPrivate.

Add a test case that verifies that the window resources is destroyed,
and that events are delivered as they should.

Done-with: Morten Johan Sørvig <morten.sorvig@qt.io>
Fixes: QTBUG-46701
Pick-to: 6.2
Change-Id: Iacb6a2c8d5e880b16b0c8f0c9257ed94bed36f5b
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

src/gui/kernel/qwindow.cpp

@@ -2254,6 +2254,7 @@ bool QWindow::close()
     if (!d->platformWindow)
         return true;
 
+    QBoolBlocker inCloseReset(d->inClose);
     return d->platformWindow->close();
 }
 

src/gui/kernel/qwindow_p.h

@@ -136,6 +136,7 @@ public:
     bool visible= false;
     bool visibilityOnDestroy = false;
     bool exposed = false;
+    bool inClose = false;
     QSurfaceFormat requestedFormat;
     QString windowTitle;
     QString windowFilePath;

src/widgets/kernel/qwidget.cpp

@@ -8360,6 +8360,24 @@ void QWidgetPrivate::hideChildren(bool spontaneous)
     }
 }
 
+/*!
+    \internal
+
+    For windows, this is called from the QWidgetWindow::handleCloseEvent implementation,
+    which QWidget::close indirectly calls by closing the QWindow. \a mode will be
+    CloseWithEvent if QWidgetWindow::handleCloseEvent is called indirectly by
+    QWindow::close, and CloseWithSpontaneousEvent if the close event originates from the
+    system (i.e. the user clicked the close button in the title bar).
+
+    QDialog calls this method directly in its hide() implementation, which might be
+    called from the QDialog::closeEvent override. \a mode will be set to CloseNoEvent
+    to prevent recursion.
+
+    For non-windows, this is called directly by QWidget::close, and \a mode will be
+    CloseWithEvent.
+
+    The function is also called by the QWidget destructor, with \a mode set to CloseNoEvent.
+*/
 bool QWidgetPrivate::close_helper(CloseMode mode)
 {
     if (data.is_closing)
@@ -8384,6 +8402,7 @@ bool QWidgetPrivate::close_helper(CloseMode mode)
         }
     }
 
+    // even for windows, make sure we deliver a hide event and that all children get hidden
     if (!that.isNull() && !q->isHidden())
         q->hide();
 
@@ -8446,6 +8465,12 @@ bool QWidgetPrivate::close_helper(CloseMode mode)
 
 bool QWidget::close()
 {
+    // Close native widgets via QWindow::close() in order to run QWindow
+    // close code. The QWidget-specific close code in close_helper() will
+    // in this case be called from the Close event handler in QWidgetWindow.
+    if (QWindow *widgetWindow = windowHandle())
+        return widgetWindow->close();
+
     return d_func()->close_helper(QWidgetPrivate::CloseWithEvent);
 }
 

src/widgets/kernel/qwidgetwindow.cpp

@@ -840,7 +840,9 @@ void QWidgetWindow::handleResizeEvent(QResizeEvent *event)
 
 void QWidgetWindow::handleCloseEvent(QCloseEvent *event)
 {
-    bool is_closing = m_widget->d_func()->close_helper(QWidgetPrivate::CloseWithSpontaneousEvent);
+    Q_D(QWidgetWindow);
+    bool is_closing = m_widget->d_func()->close_helper(d->inClose ? QWidgetPrivate::CloseWithEvent
+                                                                  : QWidgetPrivate::CloseWithSpontaneousEvent);
     event->setAccepted(is_closing);
 }
 

tests/auto/widgets/kernel/qwidget_window/tst_qwidget_window.cpp

@@ -90,6 +90,8 @@ private slots:
     void tst_show_resize();
     void tst_show_resize_hide_show();
 
+    void close();
+
     void tst_windowFilePathAndwindowTitle_data();
     void tst_windowFilePathAndwindowTitle();
     void tst_windowFilePath_data();
@@ -247,6 +249,70 @@ void tst_QWidget_window::tst_show_resize_hide_show()
     QCOMPARE(w.size(), m_testWidgetSize);
 }
 
+void tst_QWidget_window::close()
+{
+    // Verfy that closing a QWidgetWindow deletes its platform window,
+    // as expected of a QWindow subclass. This must be done also
+    // if QWidget API is used to close. The QCloseEvent must not be
+    // spontaneous if the close is triggered by a Qt API that the application
+    // would call in response to an event, and spontaneous if it is directly
+    // caused by user interaction, such as clicking the (x) in the titlebar.
+    // We can simulate this only by generating a WindowSystemEvent.
+    // Children of the window should get a hide event (never spontaneous when
+    // caused by closing the window).
+
+    struct Widget : public QWidget
+    {
+        using QWidget::QWidget;
+        int spontClose = -1;
+        int spontHide = -1;
+    protected:
+        void hideEvent(QHideEvent *e)
+        { spontHide = e->spontaneous() ? 1 : 0; }
+        void closeEvent(QCloseEvent *e)
+        { spontClose = e->spontaneous() ? 1 : 0; }
+    };
+
+    // QWindow::close()
+    {
+        Widget w;
+        Widget child(&w);
+        w.winId();
+        QVERIFY(w.windowHandle());
+        QVERIFY(w.windowHandle()->handle());
+        w.windowHandle()->close();
+        QCOMPARE(w.spontClose, 0);
+        QCOMPARE(child.spontHide, -1); // was never shown
+        QVERIFY(w.windowHandle());
+        QVERIFY(!w.windowHandle()->handle());
+    }
+
+    // QWidget::close()
+    {
+        Widget w;
+        Widget child(&w);
+        w.show();
+        QVERIFY(w.windowHandle());
+        QVERIFY(w.windowHandle()->handle());
+        w.close();
+        QCOMPARE(w.spontClose, 0);
+        QCOMPARE(child.spontHide, 0);
+        QVERIFY(w.windowHandle());
+        QVERIFY(!w.windowHandle()->handle());
+    }
+
+    // User-initiated close
+    {
+        Widget w;
+        Widget child(&w);
+        w.show();
+        QWindowSystemInterface::handleCloseEvent(w.windowHandle());
+        QApplication::processEvents();
+        QCOMPARE(w.spontClose, 1);
+        QCOMPARE(child.spontHide, 0);
+    }
+}
+
 class PaintTestWidget : public QWidget
 {
 public: