Fix offscreen rendering in QOpenGLWidget

Amends 68a4c5da9a080101cccd8a3b2edb1c908da0ca8e

In a case sharing QOpenGLContext,
offscreen renderings cannot get QOpenGLContext from Rhi.

Fixes: QTBUG-123005
Change-Id: I9baae5e5c77878885f73ee39df5cd39117e8f1c2
Reviewed-by: Tor Arne Vestbø <[email protected]>
Reviewed-by: Laszlo Agocs <[email protected]>
(cherry picked from commit 50c81f549030aba3c29f8cd161662b019028e91b)
Reviewed-by: Qt Cherry-pick Bot <[email protected]>
(cherry picked from commit 2bbfa7f18df6086c4090fa2f3823c929a1bf4ba5)
(cherry picked from commit 304666855b2cc568ce64732ae2462467944505cb)

1 files changed, 5 insertions, 3 deletions

diff --git a/src/openglwidgets/qopenglwidget.cpp b/src/openglwidgets/qopenglwidget.cpp
index 6c46f12782c..b7b339819ed 100644
--- a/src/openglwidgets/qopenglwidget.cpp
+++ b/src/openglwidgets/qopenglwidget.cpp
@@ -851,9 +851,11 @@ void QOpenGLWidgetPrivate::initialize()
 
     context = new QOpenGLContext;
     context->setFormat(requestedFormat);
-    if (contextFromRhi) {
-        context->setShareContext(contextFromRhi);
-        context->setScreen(contextFromRhi->screen());
+
+    QOpenGLContext *shareContext = contextFromRhi ? contextFromRhi : qt_gl_global_share_context();
+    if (shareContext) {
+        context->setShareContext(shareContext);
+        context->setScreen(shareContext->screen());
     }
     if (Q_UNLIKELY(!context->create())) {
         qWarning("QOpenGLWidget: Failed to create context");