Add QWidgetPrivate::rhi() helper method

For accessing the RHI managed by the widget compositing machinery.

Pick-to: 6.5
Change-Id: Ia3c1227cc2d9cfebe95611cad3dbcd7aa6f6f8c7
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>
(cherry picked from commit f451b01791536fede40c8d4fb90799c2e23e9386)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
(cherry picked from commit 9dbb295279f958e4ddd480bf9312b77643c80c0e)
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

src/openglwidgets/qopenglwidget.cpp

@@ -779,9 +779,7 @@ void QOpenGLWidgetPrivate::ensureRhiDependentResources()
 {
     Q_Q(QOpenGLWidget);
 
-    QRhi *rhi = nullptr;
+    QRhi *rhi = QWidgetPrivate::rhi();
-    if (QWidgetRepaintManager *repaintManager = QWidgetPrivate::get(q->window())->maybeRepaintManager())
-        rhi = repaintManager->rhi();
 
     // If there is no rhi, because we are completely offscreen, then there's no wrapperTexture either
     if (rhi && rhi->backend() == QRhi::OpenGLES2) {
@@ -827,7 +825,6 @@ void QOpenGLWidgetPrivate::initialize()
     // If no global shared context get our toplevel's context with which we
     // will share in order to make the texture usable by the underlying window's backingstore.
     QWidget *tlw = q->window();
-    QWidgetPrivate *tlwd = get(tlw);
 
     // Do not include the sample count. Requesting a multisampled context is not necessary
     // since we render into an FBO, never to an actual surface. What's more, attempting to
@@ -836,9 +833,7 @@ void QOpenGLWidgetPrivate::initialize()
     requestedSamples = requestedFormat.samples();
     requestedFormat.setSamples(0);
 
-    QRhi *rhi = nullptr;
+    QRhi *rhi = QWidgetPrivate::rhi();
-    if (QWidgetRepaintManager *repaintManager = tlwd->maybeRepaintManager())
-        rhi = repaintManager->rhi();
 
     // Could be that something else already initialized the window with some
     // other graphics API for the QRhi, that's not good.
@@ -1686,8 +1681,8 @@ bool QOpenGLWidget::event(QEvent *e)
             if (!QCoreApplication::testAttribute(Qt::AA_ShareOpenGLContexts))
                 d->reset();
         }
-        if (QWidgetRepaintManager *repaintManager = QWidgetPrivate::get(window())->maybeRepaintManager()) {
+        if (d->rhi()) {
-            if (!d->initialized && !size().isEmpty() && repaintManager->rhi()) {
+            if (!d->initialized && !size().isEmpty()) {
                 d->initialize();
                 if (d->initialized) {
                     d->recreateFbos();

src/widgets/kernel/qwidget.cpp

@@ -1021,6 +1021,14 @@ void QWidgetPrivate::createRecursively()
     }
 }
 
+QRhi *QWidgetPrivate::rhi() const
+{
+    if (QWidgetRepaintManager *repaintManager = maybeRepaintManager())
+        return repaintManager->rhi();
+    else
+        return nullptr;
+}
+
 /*!
     \internal
     Returns the closest parent widget that has a QWindow window handle

src/widgets/kernel/qwidget_p.h

@@ -222,6 +222,8 @@ public:
     void setSharedPainter(QPainter *painter);
     QWidgetRepaintManager *maybeRepaintManager() const;
 
+    QRhi *rhi() const;
+
     enum class WindowHandleMode {
         Direct,
         Closest,