Fix up exposing the swapchain to Quick3D

Quick3D is broken in combination with QQuickRenderControl. This is
because just exposing the swapchain is not enough - there is no
swapchain with QQuickRenderControl. Rather, one needs access to the
command buffer and render target then.

Change-Id: I6c06ad3d83ab0018b9f985073757a3378dbce24b
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

3 files changed, 30 insertions, 4 deletions

diff --git a/src/quick/scenegraph/coreapi/qsgrendererinterface.cpp b/src/quick/scenegraph/coreapi/qsgrendererinterface.cpp
index 6970aa0afb..efbab4086c 100644
--- a/src/quick/scenegraph/coreapi/qsgrendererinterface.cpp
+++ b/src/quick/scenegraph/coreapi/qsgrendererinterface.cpp
@@ -113,8 +113,19 @@ QT_BEGIN_NAMESPACE
     the scenegraph, when applicable. This value was introduced in Qt 5.14.
 
     \value RhiSwapchainResource The resource is a pointer to a QRhiSwapchain
-    instance that is associated with the window. This value was introduced in
-    Qt 6.0.
+    instance that is associated with the window. The value is null when the
+    window is used in combination with QQuickRenderControl. This value was
+    introduced in Qt 6.0.
+
+    \value RhiRedirectCommandBuffer The resource is a pointer to a
+    QRhiCommandBuffer instance that is associated with the window and its
+    QQuickRenderControl. The value is null when the window is not associated
+    with a QQuickRenderControl. This value was introduced in Qt 6.0.
+
+    \value RhiRedirectRenderTarget The resource is a pointer to a
+    QRhiTextureRenderTarget instance that is associated with the window and its
+    QQuickRenderControl. The value is null when the window is not associated
+    with a QQuickRenderControl. This value was introduced in Qt 6.0.
 
     \value PhysicalDeviceResource The resource is a pointer to the pysical
     device object used by the scenegraph, when applicable. For example, a
diff --git a/src/quick/scenegraph/coreapi/qsgrendererinterface.h b/src/quick/scenegraph/coreapi/qsgrendererinterface.h
index 9d7b9a5738..c001ecc2db 100644
--- a/src/quick/scenegraph/coreapi/qsgrendererinterface.h
+++ b/src/quick/scenegraph/coreapi/qsgrendererinterface.h
@@ -68,6 +68,8 @@ public:
         PainterResource,
         RhiResource,
         RhiSwapchainResource,
+        RhiRedirectCommandBuffer,
+        RhiRedirectRenderTarget,
         PhysicalDeviceResource,
         OpenGLContextResource,
         DeviceContextResource,
diff --git a/src/quick/scenegraph/qsgrhisupport.cpp b/src/quick/scenegraph/qsgrhisupport.cpp
index 007739d2d7..618e1f1411 100644
--- a/src/quick/scenegraph/qsgrhisupport.cpp
+++ b/src/quick/scenegraph/qsgrhisupport.cpp
@@ -441,10 +441,23 @@ const void *QSGRhiSupport::rifResource(QSGRendererInterface::Resource res,
                                        const QQuickWindow *w)
 {
     QRhi *rhi = rc->rhi();
-    if (res == QSGRendererInterface::RhiResource || !rhi)
+    if (!rhi)
+        return nullptr;
+
+    // Accessing the underlying QRhi* objects are essential both for Qt Quick
+    // 3D and advanced solutions, such as VR engine integrations.
+    switch (res) {
+    case QSGRendererInterface::RhiResource:
         return rhi;
-    if (res == QSGRendererInterface::RhiSwapchainResource)
+    case QSGRendererInterface::RhiSwapchainResource:
         return QQuickWindowPrivate::get(w)->swapchain;
+    case QSGRendererInterface::RhiRedirectCommandBuffer:
+        return QQuickWindowPrivate::get(w)->redirect.commandBuffer;
+    case QSGRendererInterface::RhiRedirectRenderTarget:
+        return QQuickWindowPrivate::get(w)->redirect.rt.renderTarget;
+    default:
+        break;
+    }
 
     const QRhiNativeHandles *nat = rhi->nativeHandles();
     if (!nat)