Fix rendercontrol grabs with the software backend

Calling grabWindow recurses (since that is implemented via
QQuickRenderControl::grab...) so it's not an option. Instead,
call directly in the software renderer implementation.

Fix also the size of the offscreen QQuickWindow when using QQuickWidget
in combination with the software backend.

Change-Id: I857a2cc0aebbbaa5d52d809aeaec37c15b0787b9
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

src/quick/items/qquickrendercontrol.cpp

@@ -56,9 +56,9 @@
 
 #include <QtQuick/QQuickWindow>
 #include <QtQuick/private/qquickwindow_p.h>
+#include <QtQuick/private/qsgsoftwarerenderer_p.h>
 #include <QtCore/private/qobject_p.h>
 
-
 QT_BEGIN_NAMESPACE
 #ifndef QT_NO_OPENGL
 extern Q_GUI_EXPORT QImage qt_gl_read_framebuffer(const QSize &size, bool alpha_format, bool include_alpha);
@@ -369,12 +369,31 @@ QImage QQuickRenderControl::grab()
     if (!d->window)
         return QImage();
 
-    render();
+    QImage grabContent;
+
+    if (d->window->rendererInterface()->graphicsApi() == QSGRendererInterface::OpenGL) {
 #ifndef QT_NO_OPENGL
-    QImage grabContent = qt_gl_read_framebuffer(d->window->size() * d->window->effectiveDevicePixelRatio(), false, false);
-#else
-    QImage grabContent = d->window->grabWindow();
+        render();
+        grabContent = qt_gl_read_framebuffer(d->window->size() * d->window->effectiveDevicePixelRatio(), false, false);
 #endif
+    } else if (d->window->rendererInterface()->graphicsApi() == QSGRendererInterface::Software) {
+        QQuickWindowPrivate *cd = QQuickWindowPrivate::get(d->window);
+        QSGSoftwareRenderer *softwareRenderer = static_cast<QSGSoftwareRenderer *>(cd->renderer);
+        if (softwareRenderer) {
+            const qreal dpr = d->window->effectiveDevicePixelRatio();
+            const QSize imageSize = d->window->size() * dpr;
+            grabContent = QImage(imageSize, QImage::Format_ARGB32_Premultiplied);
+            grabContent.setDevicePixelRatio(dpr);
+            QPaintDevice *prevDev = softwareRenderer->currentPaintDevice();
+            softwareRenderer->setCurrentPaintDevice(&grabContent);
+            softwareRenderer->markDirty();
+            render();
+            softwareRenderer->setCurrentPaintDevice(prevDev);
+        }
+    } else {
+        qWarning("QQuickRenderControl: grabs are not supported with the current Qt Quick backend");
+    }
+
     return grabContent;
 }
 

src/quick/scenegraph/adaptations/software/qsgabstractsoftwarerenderer.cpp

@@ -236,7 +236,7 @@ void QSGAbstractSoftwareRenderer::setBackgroundSize(const QSize &size)
     m_background->setRect(0.0f, 0.0f, size.width(), size.height());
     renderableNode(m_background)->markGeometryDirty();
     // Invalidate the whole scene when the background is resized
-    m_dirtyRegion = QRegion(m_background->rect().toRect());
+    markDirty();
 }
 
 QColor QSGAbstractSoftwareRenderer::backgroundColor()
@@ -322,4 +322,9 @@ void QSGAbstractSoftwareRenderer::nodeOpacityUpdated(QSGNode *node)
     m_nodeUpdater->updateNodes(node);
 }
 
+void QSGAbstractSoftwareRenderer::markDirty()
+{
+    m_dirtyRegion = QRegion(m_background->rect().toRect());
+}
+
 QT_END_NAMESPACE

src/quick/scenegraph/adaptations/software/qsgabstractsoftwarerenderer_p.h

@@ -75,6 +75,8 @@ public:
 
     void nodeChanged(QSGNode *node, QSGNode::DirtyState state) override;
 
+    void markDirty();
+
 protected:
     QRegion renderNodes(QPainter *painter);
     void buildRenderList();

src/quick/scenegraph/adaptations/software/qsgsoftwarerenderer.cpp

@@ -69,6 +69,11 @@ void QSGSoftwareRenderer::setCurrentPaintDevice(QPaintDevice *device)
     m_backingStore = nullptr;
 }
 
+QPaintDevice *QSGSoftwareRenderer::currentPaintDevice() const
+{
+    return m_paintDevice;
+}
+
 void QSGSoftwareRenderer::setBackingStore(QBackingStore *backingStore)
 {
     m_backingStore = backingStore;

src/quick/scenegraph/adaptations/software/qsgsoftwarerenderer_p.h

@@ -65,6 +65,7 @@ public:
     virtual ~QSGSoftwareRenderer();
 
     void setCurrentPaintDevice(QPaintDevice *device);
+    QPaintDevice *currentPaintDevice() const;
     void setBackingStore(QBackingStore *backingStore);
     QRegion flushRegion() const;
 

src/quickwidgets/qquickwidget.cpp

@@ -894,6 +894,12 @@ void QQuickWidget::createFramebufferObject()
     if (size().isEmpty())
         return;
 
+    // Even though this is just an offscreen window we should set the position on it, as it might be
+    // useful for an item to know the actual position of the scene.
+    // Note: The position will be update when we get a move event (see: updatePosition()).
+    const QPoint &globalPos = mapToGlobal(QPoint(0, 0));
+    d->offscreenWindow->setGeometry(globalPos.x(), globalPos.y(), width(), height());
+
     if (d->useSoftwareRenderer) {
         const QSize imageSize = size() * devicePixelRatio();
         d->softwareImage = QImage(imageSize, QImage::Format_ARGB32_Premultiplied);
@@ -961,11 +967,6 @@ void QQuickWidget::createFramebufferObject()
     }
 #endif
 
-    // Even though this is just an offscreen window we should set the position on it, as it might be
-    // useful for an item to know the actual position of the scene.
-    // Note: The position will be update when we get a move event (see: updatePosition()).
-    const QPoint &globalPos = mapToGlobal(QPoint(0, 0));
-    d->offscreenWindow->setGeometry(globalPos.x(), globalPos.y(), width(), height());
     d->offscreenWindow->setRenderTarget(d->fbo);
 
     if (samples > 0)