Squashed commit of the following:

commit 1a5e9421d9d74ebd257fc5404687bd21bea62503
Author: Uwe Rathmann <Uwe.Rathmann@tigertal.de>
Date:   Thu Dec 14 12:59:10 2023 +0100

    wip

commit db4a97a79ca5ff4f9a39223c7601d5d173862f70
Author: Uwe Rathmann <Uwe.Rathmann@tigertal.de>
Date:   Thu Dec 14 12:58:42 2023 +0100

    wip

commit 5fc7c8298f26dabd14baca942d854924109d76f2
Author: Uwe Rathmann <Uwe.Rathmann@tigertal.de>
Date:   Thu Dec 14 12:57:18 2023 +0100

    wip

commit a2a7056a1df69d1fcc5a6de7ebb6c1b99d1bf7eb
Author: Uwe Rathmann <Uwe.Rathmann@tigertal.de>
Date:   Thu Dec 14 12:50:26 2023 +0100

    wip

commit a35d79069c20e2c76ef92eec308d5eb459f110ec
Author: Uwe Rathmann <Uwe.Rathmann@tigertal.de>
Date:   Thu Dec 14 12:23:15 2023 +0100

    wip

commit d0828ee074c7a247621590b5575c587e1a876706
Author: Uwe Rathmann <Uwe.Rathmann@tigertal.de>
Date:   Thu Dec 14 11:17:37 2023 +0100

    wip

playground/parrots/SceneTexture.cpp

@@ -26,12 +26,11 @@ namespace
 
         void setFinalNode( QSGTransformNode* node )
         {
-            /*
+            if ( node != m_finalNode )
-                we need to find a way how to block all nodes
+            {
-                that are rendered behing m_finalNode TODO ...
+                m_finalNode = node;
-             */
+                m_renderPassData.setDirty();
-
+            }
-            m_finalNode = node;
         }
 
         QRhiTexture* texture() const { return m_rhiTexture; }
@@ -70,12 +69,25 @@ namespace
             setViewportRect( r );
         }
 
-        void renderScene() override
+        void render() override
         {
-            Inherited::renderScene();
+            prepareRenderPass( &m_renderPassData );
+            m_renderPassData.postPrepare( rootNode(), m_finalNode );
+
+            beginRenderPass( &m_renderPassData );
+            recordRenderPass( &m_renderPassData );
+            endRenderPass( &m_renderPassData );
         }
 
       private:
+        void nodeChanged( QSGNode* node, QSGNode::DirtyState state ) override
+        {
+            if ( state & ( QSGNode::DirtyNodeAdded | QSGNode::DirtyNodeRemoved ) )
+                m_renderPassData.setDirty();
+
+            Inherited::nodeChanged( node, state );
+        }
+
         void createTarget( const QSize& size )
         {
             const auto rhi = context()->rhi();
@@ -112,11 +124,6 @@ namespace
             m_rhiTexture = nullptr;
         }
 
-        void nodeChanged( QSGNode* node, QSGNode::DirtyState state ) override
-        {
-            Inherited::nodeChanged( node, state );
-        }
-
       private:
         inline QSGRendererInterface::RenderMode renderMode(
             QSGDefaultRenderContext* context ) const
@@ -128,6 +135,83 @@ namespace
 
         QRhiTexture* m_rhiTexture = nullptr;
         QSGTransformNode* m_finalNode = nullptr;
+
+        class RenderPassData : public RenderPassContext
+        {
+          public:
+            void setDirty()
+            {
+                m_nodesDirty = true;
+            }
+
+            void postPrepare( const QSGNode* rootNode, const QSGNode* finalNode )
+            {
+                using namespace QSGBatchRenderer;;
+
+                if ( m_nodesDirty )
+                {
+                    m_blockedNodes.clear();
+
+                    for ( auto node = finalNode;
+                        node && node != rootNode; node = node->parent() )
+                    {
+                        for ( auto sibling = node->nextSibling();
+                            sibling != nullptr; sibling = sibling->nextSibling() )
+                        {
+                            markNodesAsBlocked( sibling );
+                        }
+                    }
+
+                    m_nodesDirty = false;
+                }
+
+                for ( const auto& renderBatch : opaqueRenderBatches )
+                {
+                    auto batch = const_cast< Batch* >( renderBatch.batch );
+                    removeBlockedNodes( batch );
+                }
+
+                for ( auto& renderBatch : alphaRenderBatches )
+                {
+                    auto batch = const_cast< Batch* >( renderBatch.batch );
+                    removeBlockedNodes( batch );
+                }
+            }
+
+          private:
+            void markNodesAsBlocked( const QSGNode* node )
+            {
+                if ( node->type() == QSGNode::GeometryNodeType )
+                {
+                    auto n = static_cast< const QSGGeometryNode* >( node );
+                    m_blockedNodes.insert( n );
+                }
+
+                for ( auto child = node->firstChild();
+                    child != nullptr; child = child->nextSibling() )
+                {
+                    markNodesAsBlocked( child );
+                }
+            }
+
+            void removeBlockedNodes( QSGBatchRenderer::Batch* batch )
+            {
+                QSGBatchRenderer::Element** elementRef = &batch->first;
+
+                while( auto element = *elementRef )
+                {
+                    if ( m_blockedNodes.contains( element->node ) )
+                        *elementRef = element->nextInBatch;
+                    else
+                        elementRef = &element->nextInBatch;
+                }
+            }
+
+            bool m_nodesDirty = true;
+            QSet< const QSGGeometryNode* > m_blockedNodes;
+        };
+
+        RenderPassData m_renderPassData;
     };
 };
 

playground/parrots/main.cpp

@@ -22,10 +22,10 @@
 
 #include "Overlay.h"
 
-class ButtonBox : public QskLinearBox
+class ForegroundItem : public QskLinearBox
 {
   public:
-    ButtonBox( QQuickItem* parent = nullptr )
+    ForegroundItem( QQuickItem* parent = nullptr )
         : QskLinearBox( Qt::Vertical, parent )
     {
         setMargins( 20 );
@@ -39,6 +39,10 @@ class ButtonBox : public QskLinearBox
 
         auto button = new QskPushButton( "Button", this );
         button->setLayoutAlignmentHint( Qt::AlignHCenter | Qt::AlignBottom );
+
+        label->setObjectName( "miniParrots" );
+        button->setObjectName( "button" );
+        setObjectName( "foreground" );
     }
 };
 
@@ -50,6 +54,7 @@ class OverlayBox : public Overlay
     OverlayBox( QQuickItem* parent = nullptr )
         : Inherited( parent )
     {
+        setObjectName( "overlay" );
     }
 
   protected:
@@ -86,6 +91,9 @@ class BackgroundItem : public QskControl
         m_label->setGraphic( QskGraphic::fromImage( image ) );
 
         startTimer( 20 );
+
+        setObjectName( "background" );
+        m_label->setObjectName( "parrots" );
     }
 
   protected:
@@ -135,13 +143,15 @@ class MainView : public QskControl
         m_background = new BackgroundItem( this );
 
         m_overlay = new OverlayBox( m_background );
-        (void )new ButtonBox( m_overlay );
+        (void )new ForegroundItem( m_overlay );
 
-#if 0
+#if 1
         auto box = new QskBox( m_background );
         box->setGeometry( 50, 50, 400, 200 );
         box->setFillGradient( Qt::darkBlue );
+        box->setObjectName( "blueBox" );
 #endif
+        setObjectName( "mainView" );
     }
 
   protected: