QQuickWidget: expose the underlying QQuickWindow

There's a number of APIs (such as all the scenegraph-related
signals) that are currently missing from QQuickWidget.
Instead of duplicating every API in QQuickWidget, simply expose
the underlying offscreen QQuickWindow.

Task-number: QTBUG-45260
Change-Id: I1a89fe600ce675963ea24ee6dd56d6ca4fea9cd2
Reviewed-by: Andy Shaw <andy.shaw@digia.com>
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>
Reviewed-by: Laszlo Agocs <laszlo.agocs@theqtcompany.com>

3 files changed, 54 insertions, 0 deletions

diff --git a/src/quickwidgets/qquickwidget.cpp b/src/quickwidgets/qquickwidget.cpp
index c4100551d0..b472664068 100644
--- a/src/quickwidgets/qquickwidget.cpp
+++ b/src/quickwidgets/qquickwidget.cpp
@@ -1218,4 +1218,23 @@ void QQuickWidget::setClearColor(const QColor &color)
     d->offscreenWindow->setColor(color);
 }
 
+/*!
+    \since 5.5
+
+    Returns the offscreen QQuickWindow which is used by this widget to drive
+    the Qt Quick rendering. This is useful if you want to use QQuickWindow
+    APIs that are not currently exposed by QQuickWidget, for instance
+    connecting to the QQuickWindow::beforeRendering() signal in order
+    to draw native OpenGL content below Qt Quick's own rendering.
+
+    \warning Use the return value of this function with caution. In
+    particular, do not ever attempt to show the QQuickWindow, and be
+    very careful when using other QWindow-only APIs.
+*/
+QQuickWindow *QQuickWidget::quickWindow() const
+{
+    Q_D(const QQuickWidget);
+    return d->offscreenWindow;
+}
+
 QT_END_NAMESPACE
diff --git a/src/quickwidgets/qquickwidget.h b/src/quickwidgets/qquickwidget.h
index b961a6eeaf..a8bf03edfb 100644
--- a/src/quickwidgets/qquickwidget.h
+++ b/src/quickwidgets/qquickwidget.h
@@ -90,6 +90,8 @@ public:
 
     void setClearColor(const QColor &color);
 
+    QQuickWindow *quickWindow() const;
+
 public Q_SLOTS:
     void setSource(const QUrl&);
     void setContent(const QUrl& url, QQmlComponent *component, QObject *item);
diff --git a/tests/auto/quickwidgets/qquickwidget/tst_qquickwidget.cpp b/tests/auto/quickwidgets/qquickwidget/tst_qquickwidget.cpp
index 1d9e40011d..3da920ca27 100644
--- a/tests/auto/quickwidgets/qquickwidget/tst_qquickwidget.cpp
+++ b/tests/auto/quickwidgets/qquickwidget/tst_qquickwidget.cpp
@@ -58,6 +58,7 @@ private slots:
     void errors();
     void engine();
     void readback();
+    void renderingSignals();
 };
 
 
@@ -259,6 +260,38 @@ void tst_qquickwidget::readback()
     QCOMPARE(pix, qRgb(255, 0, 0));
 }
 
+void tst_qquickwidget::renderingSignals()
+{
+    QQuickWidget widget;
+    QQuickWindow *window = widget.quickWindow();
+    QVERIFY(window);
+
+    QSignalSpy beforeRenderingSpy(window, &QQuickWindow::beforeRendering);
+    QSignalSpy beforeSyncSpy(window, &QQuickWindow::beforeSynchronizing);
+    QSignalSpy afterRenderingSpy(window, &QQuickWindow::afterRendering);
+
+    QVERIFY(beforeRenderingSpy.isValid());
+    QVERIFY(beforeSyncSpy.isValid());
+    QVERIFY(afterRenderingSpy.isValid());
+
+    QCOMPARE(beforeRenderingSpy.size(), 0);
+    QCOMPARE(beforeSyncSpy.size(), 0);
+    QCOMPARE(afterRenderingSpy.size(), 0);
+
+    widget.setSource(testFileUrl("rectangle.qml"));
+
+    QCOMPARE(beforeRenderingSpy.size(), 0);
+    QCOMPARE(beforeSyncSpy.size(), 0);
+    QCOMPARE(afterRenderingSpy.size(), 0);
+
+    widget.show();
+    QVERIFY(QTest::qWaitForWindowExposed(&widget, 5000));
+
+    QTRY_VERIFY(beforeRenderingSpy.size() > 0);
+    QTRY_VERIFY(beforeSyncSpy.size() > 0);
+    QTRY_VERIFY(afterRenderingSpy.size() > 0);
+}
+
 QTEST_MAIN(tst_qquickwidget)
 
 #include "tst_qquickwidget.moc"