rendernode example: Prevent gui-render thread data race

By taking things like the item width and height in updatePaintNode()
(while gui is locked).

Change-Id: I840c6c858a0478eb6ceb09653fd1e033cb54372d
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

9 files changed, 114 insertions, 81 deletions

diff --git a/examples/quick/scenegraph/rendernode/customrenderitem.cpp b/examples/quick/scenegraph/rendernode/customrenderitem.cpp
index 67a9cccfc6..8aaa56c359 100644
--- a/examples/quick/scenegraph/rendernode/customrenderitem.cpp
+++ b/examples/quick/scenegraph/rendernode/customrenderitem.cpp
@@ -70,48 +70,56 @@ CustomRenderItem::CustomRenderItem(QQuickItem *parent)
 QSGNode *CustomRenderItem::updatePaintNode(QSGNode *node, UpdatePaintNodeData *)
 {
     QSGRenderNode *n = static_cast<QSGRenderNode *>(node);
-    if (!n) {
-        QSGRendererInterface *ri = window()->rendererInterface();
-        if (!ri)
-            return nullptr;
-        switch (ri->graphicsApi()) {
-        case QSGRendererInterface::OpenGL:
-            Q_FALLTHROUGH();
-        case QSGRendererInterface::OpenGLRhi:
+
+    QSGRendererInterface *ri = window()->rendererInterface();
+    if (!ri)
+        return nullptr;
+
+    switch (ri->graphicsApi()) {
+    case QSGRendererInterface::OpenGL:
+        Q_FALLTHROUGH();
+    case QSGRendererInterface::OpenGLRhi:
 #if QT_CONFIG(opengl)
-            n = new OpenGLRenderNode(this);
+        if (!n)
+            n = new OpenGLRenderNode;
+        static_cast<OpenGLRenderNode *>(n)->sync(this);
 #endif
-            break;
+        break;
 
-        case QSGRendererInterface::MetalRhi:
+    case QSGRendererInterface::MetalRhi:
 #ifdef Q_OS_DARWIN
-        {
-            MetalRenderNode *metalNode = new MetalRenderNode(this);
+        if (!n) {
+            MetalRenderNode *metalNode = new MetalRenderNode;
             n = metalNode;
             metalNode->resourceBuilder()->setWindow(window());
             QObject::connect(window(), &QQuickWindow::beforeRendering,
                              metalNode->resourceBuilder(), &MetalRenderNodeResourceBuilder::build);
         }
+        static_cast<MetalRenderNode *>(n)->sync(this);
 #endif
-            break;
+        break;
 
-        case QSGRendererInterface::Direct3D12: // ### Qt 6: remove
+    case QSGRendererInterface::Direct3D12: // ### Qt 6: remove
 #if QT_CONFIG(d3d12)
-            n = new D3D12RenderNode(this);
+        if (!n)
+            n = new D3D12RenderNode;
+        static_cast<D3D12RenderNode *>(n)->sync(this);
 #endif
-            break;
+        break;
 
-        case QSGRendererInterface::Software:
-            n = new SoftwareRenderNode(this);
-            break;
-
-        default:
-            break;
-        }
+    case QSGRendererInterface::Software:
         if (!n)
-            qWarning("QSGRendererInterface reports unknown graphics API %d", ri->graphicsApi());
+            n = new SoftwareRenderNode;
+        static_cast<SoftwareRenderNode *>(n)->sync(this);
+        break;
+
+    default:
+        break;
     }
 
+    if (!n)
+        qWarning("QSGRendererInterface reports unknown graphics API %d", ri->graphicsApi());
+
     return n;
 }
 //! [2]
diff --git a/examples/quick/scenegraph/rendernode/d3d12renderer.cpp b/examples/quick/scenegraph/rendernode/d3d12renderer.cpp
index 878b022950..e85811c089 100644
--- a/examples/quick/scenegraph/rendernode/d3d12renderer.cpp
+++ b/examples/quick/scenegraph/rendernode/d3d12renderer.cpp
@@ -58,11 +58,6 @@
 
 #if QT_CONFIG(d3d12)
 
-D3D12RenderNode::D3D12RenderNode(QQuickItem *item)
-    : m_item(item)
-{
-}
-
 D3D12RenderNode::~D3D12RenderNode()
 {
     releaseResources();
@@ -87,8 +82,8 @@ void D3D12RenderNode::releaseResources()
 
 void D3D12RenderNode::init()
 {
-    QSGRendererInterface *rif = m_item->window()->rendererInterface();
-    m_device = static_cast<ID3D12Device *>(rif->getResource(m_item->window(), QSGRendererInterface::DeviceResource));
+    QSGRendererInterface *rif = m_window->rendererInterface();
+    m_device = static_cast<ID3D12Device *>(rif->getResource(m_window, QSGRendererInterface::DeviceResource));
     Q_ASSERT(m_device);
 
     D3D12_ROOT_PARAMETER rootParameter;
@@ -178,7 +173,7 @@ void D3D12RenderNode::init()
     psoDesc.DSVFormat = DXGI_FORMAT_D24_UNORM_S8_UINT; // not in use due to !DepthEnable, but this would be the correct format otherwise
     // We are rendering on the default render target so if the QuickWindow/View
     // has requested samples > 0 then we have to follow suit.
-    const uint samples = qMax(1, m_item->window()->format().samples());
+    const uint samples = qMax(1, m_window->format().samples());
     psoDesc.SampleDesc.Count = samples;
     if (samples > 1) {
         D3D12_FEATURE_DATA_MULTISAMPLE_QUALITY_LEVELS msaaInfo = {};
@@ -257,9 +252,9 @@ void D3D12RenderNode::render(const RenderState *state)
     if (!m_device)
         init();
 
-    QSGRendererInterface *rif = m_item->window()->rendererInterface();
+    QSGRendererInterface *rif = m_window->rendererInterface();
     ID3D12GraphicsCommandList *commandList = static_cast<ID3D12GraphicsCommandList *>(
-        rif->getResource(m_item->window(), QSGRendererInterface::CommandListResource));
+        rif->getResource(m_window, QSGRendererInterface::CommandListResource));
     Q_ASSERT(commandList);
 
     const int msize = 16 * sizeof(float);
@@ -268,9 +263,9 @@ void D3D12RenderNode::render(const RenderState *state)
     const float opacity = inheritedOpacity();
     memcpy(cbPtr + 2 * msize, &opacity, sizeof(float));
 
-    const QPointF p0(m_item->width() - 1, m_item->height() - 1);
+    const QPointF p0(m_width - 1, m_height - 1);
     const QPointF p1(0, 0);
-    const QPointF p2(0, m_item->height() - 1);
+    const QPointF p2(0, m_height - 1);
 
     float *vp = reinterpret_cast<float *>(vbPtr);
     *vp++ = p0.x();
@@ -301,7 +296,14 @@ QSGRenderNode::RenderingFlags D3D12RenderNode::flags() const
 
 QRectF D3D12RenderNode::rect() const
 {
-    return QRect(0, 0, m_item->width(), m_item->height());
+    return QRect(0, 0, m_width, m_height);
+}
+
+void D3D12RenderNode::sync(QQuickItem *item)
+{
+    m_window = item->window();
+    m_width = item->width();
+    m_height = item->height();
 }
 
 #endif // d3d12
diff --git a/examples/quick/scenegraph/rendernode/d3d12renderer.h b/examples/quick/scenegraph/rendernode/d3d12renderer.h
index ec4b5f85e8..7186b72c04 100644
--- a/examples/quick/scenegraph/rendernode/d3d12renderer.h
+++ b/examples/quick/scenegraph/rendernode/d3d12renderer.h
@@ -52,11 +52,10 @@
 #define D3D12RENDERER_H
 
 #include <qsgrendernode.h>
+#include <QQuickItem>
 
 #if QT_CONFIG(d3d12)
 
-QT_FORWARD_DECLARE_CLASS(QQuickItem)
-
 #include <d3d12.h>
 #include <wrl/client.h>
 
@@ -65,7 +64,6 @@ using namespace Microsoft::WRL;
 class D3D12RenderNode : public QSGRenderNode
 {
 public:
-    D3D12RenderNode(QQuickItem *item);
     ~D3D12RenderNode();
 
     void render(const RenderState *state) override;
@@ -73,10 +71,15 @@ public:
     RenderingFlags flags() const override;
     QRectF rect() const override;
 
+    void sync(QQuickItem *item);
+
 private:
     void init();
 
-    QQuickItem *m_item;
+    QQuickWindow *m_window = nullptr;
+    int m_width = 0;
+    int m_height = 0;
+
     ID3D12Device *m_device = nullptr;
     ComPtr<ID3D12PipelineState> pipelineState;
     ComPtr<ID3D12RootSignature> rootSignature;
diff --git a/examples/quick/scenegraph/rendernode/metalrenderer.h b/examples/quick/scenegraph/rendernode/metalrenderer.h
index 77c9892313..31387a0e24 100644
--- a/examples/quick/scenegraph/rendernode/metalrenderer.h
+++ b/examples/quick/scenegraph/rendernode/metalrenderer.h
@@ -52,14 +52,12 @@
 #define METALRENDERER_H
 
 #include <qsgrendernode.h>
+#include <QQuickItem>
 
 #ifdef Q_OS_DARWIN
 
 QT_BEGIN_NAMESPACE
 
-class QQuickItem;
-class QQuickWindow;
-
 QT_END_NAMESPACE
 
 class MetalRenderNodeResourceBuilder : public QObject
@@ -79,7 +77,7 @@ private:
 class MetalRenderNode : public QSGRenderNode
 {
 public:
-    MetalRenderNode(QQuickItem *item);
+    MetalRenderNode();
     ~MetalRenderNode();
 
     void render(const RenderState *state) override;
@@ -90,9 +88,14 @@ public:
 
     MetalRenderNodeResourceBuilder *resourceBuilder() { return &m_resourceBuilder; }
 
+    void sync(QQuickItem *item);
+
 private:
-    QQuickItem *m_item;
     MetalRenderNodeResourceBuilder m_resourceBuilder;
+    QQuickWindow *m_window = nullptr;
+    int m_width = 0;
+    int m_height = 0;
+    int m_outputHeight = 0;
 };
 
 #endif // Q_OS_DARWIN
diff --git a/examples/quick/scenegraph/rendernode/metalrenderer.mm b/examples/quick/scenegraph/rendernode/metalrenderer.mm
index 4cb973abee..11db276f37 100644
--- a/examples/quick/scenegraph/rendernode/metalrenderer.mm
+++ b/examples/quick/scenegraph/rendernode/metalrenderer.mm
@@ -214,8 +214,7 @@ void MetalRenderNodeResourceBuilder::build()
     }
 }
 
-MetalRenderNode::MetalRenderNode(QQuickItem *item)
-    : m_item(item)
+MetalRenderNode::MetalRenderNode()
 {
     g.vs.first = g.fs.first = nil;
     g.vs.second = g.fs.second = nil;
@@ -258,14 +257,14 @@ void MetalRenderNode::releaseResources()
 
 void MetalRenderNode::render(const RenderState *state)
 {
-    QQuickWindow *window = m_item->window();
-    const QQuickWindow::GraphicsStateInfo *stateInfo = window->graphicsStateInfo();
+    Q_ASSERT(m_window);
+    const QQuickWindow::GraphicsStateInfo *stateInfo = m_window->graphicsStateInfo();
     id<MTLBuffer> vbuf = g.vbuf[stateInfo->currentFrameSlot];
     id<MTLBuffer> ubuf = g.ubuf[stateInfo->currentFrameSlot];
 
-    QPointF p0(m_item->width() - 1, m_item->height() - 1);
+    QPointF p0(m_width - 1, m_height - 1);
     QPointF p1(0, 0);
-    QPointF p2(0, m_item->height() - 1);
+    QPointF p2(0, m_height - 1);
 
     float vertices[6] = { float(p0.x()), float(p0.y()),
                           float(p1.x()), float(p1.y()),
@@ -280,9 +279,9 @@ void MetalRenderNode::render(const RenderState *state)
     memcpy(p, mvp.constData(), 64);
     memcpy(p + 64, &opacity, 4);
 
-    QSGRendererInterface *rif = window->rendererInterface();
+    QSGRendererInterface *rif = m_window->rendererInterface();
     id<MTLRenderCommandEncoder> encoder = (id<MTLRenderCommandEncoder>) rif->getResource(
-                window, QSGRendererInterface::CommandEncoderResource);
+                m_window, QSGRendererInterface::CommandEncoderResource);
     Q_ASSERT(encoder);
 
     [encoder setVertexBuffer: vbuf offset: 0 atIndex: 1];
@@ -296,7 +295,7 @@ void MetalRenderNode::render(const RenderState *state)
         const QRect r = state->scissorRect(); // bottom-up
         MTLScissorRect s;
         s.x = r.x();
-        s.y = (window->height() * window->effectiveDevicePixelRatio()) - (r.y() + r.height());
+        s.y = m_outputHeight - (r.y() + r.height());
         s.width = r.width();
         s.height = r.height();
         [encoder setScissorRect: s];
@@ -322,5 +321,13 @@ QSGRenderNode::RenderingFlags MetalRenderNode::flags() const
 
 QRectF MetalRenderNode::rect() const
 {
-    return QRect(0, 0, m_item->width(), m_item->height());
+    return QRect(0, 0, m_width, m_height);
+}
+
+void MetalRenderNode::sync(QQuickItem *item)
+{
+    m_window = item->window();
+    m_width = item->width();
+    m_height = item->height();
+    m_outputHeight = m_window->height() * m_window->effectiveDevicePixelRatio();
 }
diff --git a/examples/quick/scenegraph/rendernode/openglrenderer.cpp b/examples/quick/scenegraph/rendernode/openglrenderer.cpp
index 0633731617..a4e619bea9 100644
--- a/examples/quick/scenegraph/rendernode/openglrenderer.cpp
+++ b/examples/quick/scenegraph/rendernode/openglrenderer.cpp
@@ -58,11 +58,6 @@
 #include <QOpenGLFunctions>
 
 //! [1]
-OpenGLRenderNode::OpenGLRenderNode(QQuickItem *item)
-    : m_item(item)
-{
-}
-
 OpenGLRenderNode::~OpenGLRenderNode()
 {
     releaseResources();
@@ -138,9 +133,9 @@ void OpenGLRenderNode::render(const RenderState *state)
     m_vbo->bind();
 
 //! [5]
-    QPointF p0(m_item->width() - 1, m_item->height() - 1);
+    QPointF p0(m_width - 1, m_height - 1);
     QPointF p1(0, 0);
-    QPointF p2(0, m_item->height() - 1);
+    QPointF p2(0, m_height - 1);
 
     GLfloat vertices[6] = { GLfloat(p0.x()), GLfloat(p0.y()),
                             GLfloat(p1.x()), GLfloat(p1.y()),
@@ -192,8 +187,14 @@ QSGRenderNode::RenderingFlags OpenGLRenderNode::flags() const
 
 QRectF OpenGLRenderNode::rect() const
 {
-    return QRect(0, 0, m_item->width(), m_item->height());
+    return QRect(0, 0, m_width, m_height);
 }
 //! [4]
 
+void OpenGLRenderNode::sync(QQuickItem *item)
+{
+    m_width = item->width();
+    m_height = item->height();
+}
+
 #endif // opengl
diff --git a/examples/quick/scenegraph/rendernode/openglrenderer.h b/examples/quick/scenegraph/rendernode/openglrenderer.h
index 8d2d3caad1..1e7977481a 100644
--- a/examples/quick/scenegraph/rendernode/openglrenderer.h
+++ b/examples/quick/scenegraph/rendernode/openglrenderer.h
@@ -52,12 +52,12 @@
 #define OPENGLRENDERER_H
 
 #include <qsgrendernode.h>
+#include <QQuickItem>
 
 #if QT_CONFIG(opengl)
 
 QT_BEGIN_NAMESPACE
 
-class QQuickItem;
 class QOpenGLShaderProgram;
 class QOpenGLBuffer;
 
@@ -67,7 +67,6 @@ QT_END_NAMESPACE
 class OpenGLRenderNode : public QSGRenderNode
 {
 public:
-    OpenGLRenderNode(QQuickItem *item);
     ~OpenGLRenderNode();
 
     void render(const RenderState *state) override;
@@ -77,10 +76,13 @@ public:
     QRectF rect() const override;
 //! [1]
 
+    void sync(QQuickItem *item);
+
 private:
     void init();
 
-    QQuickItem *m_item;
+    int m_width = 0;
+    int m_height = 0;
     QOpenGLShaderProgram *m_program = nullptr;
     int m_matrixUniform;
     int m_opacityUniform;
diff --git a/examples/quick/scenegraph/rendernode/softwarerenderer.cpp b/examples/quick/scenegraph/rendernode/softwarerenderer.cpp
index 0a0ec4b485..bba364ac97 100644
--- a/examples/quick/scenegraph/rendernode/softwarerenderer.cpp
+++ b/examples/quick/scenegraph/rendernode/softwarerenderer.cpp
@@ -54,11 +54,6 @@
 #include <QSGRendererInterface>
 #include <QPainter>
 
-SoftwareRenderNode::SoftwareRenderNode(QQuickItem *item)
-    : m_item(item)
-{
-}
-
 SoftwareRenderNode::~SoftwareRenderNode()
 {
     releaseResources();
@@ -70,8 +65,10 @@ void SoftwareRenderNode::releaseResources()
 
 void SoftwareRenderNode::render(const RenderState *renderState)
 {
-    QSGRendererInterface *rif = m_item->window()->rendererInterface();
-    QPainter *p = static_cast<QPainter *>(rif->getResource(m_item->window(), QSGRendererInterface::PainterResource));
+    Q_ASSERT(m_window);
+
+    QSGRendererInterface *rif = m_window->rendererInterface();
+    QPainter *p = static_cast<QPainter *>(rif->getResource(m_window, QSGRendererInterface::PainterResource));
     Q_ASSERT(p);
 
     const QRegion *clipRegion = renderState->clipRegion();
@@ -81,15 +78,15 @@ void SoftwareRenderNode::render(const RenderState *renderState)
     p->setTransform(matrix()->toTransform());
     p->setOpacity(inheritedOpacity());
 
-    const QPointF p0(m_item->width() - 1, m_item->height() - 1);
+    const QPointF p0(m_width - 1, m_height - 1);
     const QPointF p1(0, 0);
-    const QPointF p2(0, m_item->height() - 1);
+    const QPointF p2(0, m_height - 1);
     QPainterPath path(p0);
     path.lineTo(p1);
     path.lineTo(p2);
     path.closeSubpath();
 
-    QLinearGradient gradient(QPointF(0, 0), QPointF(m_item->width(), m_item->height()));
+    QLinearGradient gradient(QPointF(0, 0), QPointF(m_width, m_height));
     gradient.setColorAt(0, Qt::green);
     gradient.setColorAt(1, Qt::red);
 
@@ -108,5 +105,12 @@ QSGRenderNode::RenderingFlags SoftwareRenderNode::flags() const
 
 QRectF SoftwareRenderNode::rect() const
 {
-    return QRect(0, 0, m_item->width(), m_item->height());
+    return QRect(0, 0, m_width, m_height);
+}
+
+void SoftwareRenderNode::sync(QQuickItem *item)
+{
+    m_window = item->window();
+    m_width = item->width();
+    m_height = item->height();
 }
diff --git a/examples/quick/scenegraph/rendernode/softwarerenderer.h b/examples/quick/scenegraph/rendernode/softwarerenderer.h
index cc2aaf7ed3..6091a13ca3 100644
--- a/examples/quick/scenegraph/rendernode/softwarerenderer.h
+++ b/examples/quick/scenegraph/rendernode/softwarerenderer.h
@@ -57,7 +57,6 @@
 class SoftwareRenderNode : public QSGRenderNode
 {
 public:
-    SoftwareRenderNode(QQuickItem *item);
     ~SoftwareRenderNode();
 
     void render(const RenderState *state) override;
@@ -66,8 +65,12 @@ public:
     RenderingFlags flags() const override;
     QRectF rect() const override;
 
+    void sync(QQuickItem *item);
+
 private:
-    QQuickItem *m_item;
+    QQuickWindow *m_window = nullptr;
+    int m_width = 0;
+    int m_height = 0;
 };
 
 #endif