blocking updates for nodes that are not part of the QskSceneTexture

playground/parrots/Overlay.cpp

@@ -152,7 +152,6 @@ namespace
                 const bool useRhi = qskRenderingHardwareInterface( window );
 
                 textureNode = new FilterNode( useRhi, texture );
-                texture->setTextureNode( textureNode );
             }
 
             auto texture = qobject_cast< QskSceneTexture* >( textureNode->texture() );

src/nodes/QskSceneTexture.cpp

@@ -29,6 +29,26 @@ QSK_QT_PRIVATE_END
 #include <qopenglframebufferobject.h>
 #endif
 
+static int qskRenderOrderCompare( const QSGNode* rootNode,
+    const QSGNode* node1, const QSGNode* node2 )
+{
+    if ( rootNode == node1 )
+        return 1;
+            
+    if ( rootNode == node2 )
+        return -1;
+
+    for ( auto node = rootNode->firstChild();
+        node != nullptr; node = node->nextSibling() )
+    {   
+        const auto ret = qskRenderOrderCompare( node, node1, node2 );
+        if ( ret ) 
+            return ret;
+    }       
+    
+    return 0;
+}   
+
 namespace
 {
 #if QT_VERSION >= QT_VERSION_CHECK( 6, 0, 0 )
@@ -84,6 +104,7 @@ namespace
       private:
         void createTarget( const QSize& );
         void clearTarget();
+        void markDirty();
 
         QSGTransformNode* m_finalNode = nullptr;
         QskSceneTexture* m_texture = nullptr;
@@ -114,6 +135,9 @@ namespace
         , m_texture( texture )
     {
         setClearColor( Qt::transparent );
+
+        connect( this, &QSGRenderer::sceneGraphChanged,
+            this, &Renderer::markDirty );
     }
 
     Renderer::~Renderer()
@@ -126,6 +150,7 @@ namespace
         if ( node != m_finalNode )
         {
             m_finalNode = node;
+            markDirty();
         }
     }
 
@@ -205,16 +230,25 @@ namespace
 
     void Renderer::nodeChanged( QSGNode* node, QSGNode::DirtyState state )
     {
-        Inherited::nodeChanged( node, state );
-
         /*
-            We want to limit updates to nodes, that are actually rendered. TODO ...
+            No need to update the texture for changes of nodes behind
+            the final node.
 
-            In any case we need to block update requests, when the textureNode reports
-            that it has been updated by us to the renderer of the window.
+            Unfortunately QQuickWindow does not update the scene graph in
+            rendering order and we might be called for relevant nodes after
+            the texture has already  been updated. In these situations we
+            update the texture twice. Not so good ...
          */
-        if ( ( state != QSGNode::DirtyMaterial )
-            || ( node != m_texture->textureNode() ) )
+        if ( qskRenderOrderCompare( rootNode(), node, m_finalNode ) > 0 ) 
+        {
+            // triggering QSGRenderer::sceneGraphChanged signals
+            Inherited::nodeChanged( node, state );
+        }
+    }
+
+    void Renderer::markDirty()
+    {
+        if ( !m_dirty )
         {
             m_dirty = true;
             Q_EMIT m_texture->updateRequested();
@@ -352,8 +386,6 @@ class QskSceneTexturePrivate final : public QSGTexturePrivate
 
     Renderer* renderer = nullptr;
     QSGDefaultRenderContext* context = nullptr;
-
-    const QSGGeometryNode* textureNode = nullptr;
 };
 
 QskSceneTexture::QskSceneTexture( const QQuickWindow* window )
@@ -367,16 +399,6 @@ QskSceneTexture::~QskSceneTexture()
     delete d_func()->renderer;
 }
 
-void QskSceneTexture::setTextureNode( const QSGGeometryNode* node )
-{
-    d_func()->textureNode = node;
-}
-
-const QSGGeometryNode* QskSceneTexture::textureNode() const
-{
-    return d_func()->textureNode;
-}
-
 QSize QskSceneTexture::textureSize() const
 {
     Q_D( const QskSceneTexture );

src/nodes/QskSceneTexture.h

@@ -13,7 +13,6 @@ class QskSceneTexturePrivate;
 
 class QSGRootNode;
 class QSGTransformNode;
-class QSGGeometryNode;
 class QQuickWindow;
 
 class QSK_EXPORT QskSceneTexture : public QSGTexture
@@ -26,12 +25,6 @@ class QSK_EXPORT QskSceneTexture : public QSGTexture
     QskSceneTexture( const QQuickWindow* );
     ~QskSceneTexture();
 
-#if 1
-    // to avoid recursive update - need to find a better solution TODO
-    void setTextureNode( const QSGGeometryNode* );
-    const QSGGeometryNode* textureNode() const;
-#endif
-
     void render( const QSGRootNode*, const QSGTransformNode*, const QRectF& );
 
     QSize textureSize() const override;