5 files changed, 26 insertions, 7 deletions
diff --git a/src/quick/items/qquickimagebase.cpp b/src/quick/items/qquickimagebase.cpp
index 5ec3e81727..1a5d115a3c 100644
--- a/src/quick/items/qquickimagebase.cpp
+++ b/src/quick/items/qquickimagebase.cpp
@@ -206,7 +206,7 @@ void QQuickImageBase::load()
             options |= QQuickPixmap::Cache;
         d->pix.clear(this);
 
-        const qreal targetDevicePixelRatio = (window() ? window()->devicePixelRatio() : qApp->devicePixelRatio());
+        const qreal targetDevicePixelRatio = (window() ? window()->effectiveDevicePixelRatio() : qApp->devicePixelRatio());
         d->devicePixelRatio = 1.0;
 
         QUrl loadUrl = d->url;
diff --git a/src/quick/items/qquickrendercontrol.cpp b/src/quick/items/qquickrendercontrol.cpp
index 79db80595b..7ccd3a0fb4 100644
--- a/src/quick/items/qquickrendercontrol.cpp
+++ b/src/quick/items/qquickrendercontrol.cpp
@@ -318,7 +318,7 @@ QImage QQuickRenderControl::grab()
         return QImage();
 
     render();
-    QImage grabContent = qt_gl_read_framebuffer(d->window->size() * d->window->devicePixelRatio(), false, false);
+    QImage grabContent = qt_gl_read_framebuffer(d->window->size() * d->window->effectiveDevicePixelRatio(), false, false);
     return grabContent;
 }
 
diff --git a/src/quick/items/qquickshadereffectsource.cpp b/src/quick/items/qquickshadereffectsource.cpp
index 52e5ba2464..ccff98828c 100644
--- a/src/quick/items/qquickshadereffectsource.cpp
+++ b/src/quick/items/qquickshadereffectsource.cpp
@@ -628,7 +628,7 @@ QSGNode *QQuickShaderEffectSource::updatePaintNode(QSGNode *oldNode, UpdatePaint
 
     // Crate large textures on high-dpi displays.
     if (sourceItem())
-        textureSize *= d->window->devicePixelRatio();
+        textureSize *= d->window->effectiveDevicePixelRatio();
 
     const QSize minTextureSize = d->sceneGraphContext()->minimumFBOSize();
     // Keep power-of-two by doubling the size.
@@ -637,7 +637,7 @@ QSGNode *QQuickShaderEffectSource::updatePaintNode(QSGNode *oldNode, UpdatePaint
     while (textureSize.height() < minTextureSize.height())
         textureSize.rheight() *= 2;
 
-    m_texture->setDevicePixelRatio(d->window->devicePixelRatio());
+    m_texture->setDevicePixelRatio(d->window->effectiveDevicePixelRatio());
     m_texture->setSize(textureSize);
     m_texture->setRecursive(m_recursive);
     m_texture->setFormat(GLenum(m_format));
diff --git a/src/quick/items/qquickwindow.cpp b/src/quick/items/qquickwindow.cpp
index 4ec901ceb4..f6c1412aff 100644
--- a/src/quick/items/qquickwindow.cpp
+++ b/src/quick/items/qquickwindow.cpp
@@ -365,7 +365,7 @@ void QQuickWindowPrivate::renderSceneGraph(const QSize &size)
     emit q->beforeRendering();
     runAndClearJobs(&beforeRenderingJobs);
     int fboId = 0;
-    const qreal devicePixelRatio = q->devicePixelRatio();
+    const qreal devicePixelRatio = q->effectiveDevicePixelRatio();
     renderer->setDeviceRect(QRect(QPoint(0, 0), size * devicePixelRatio));
     if (renderTargetId) {
         fboId = renderTargetId;
@@ -374,7 +374,7 @@ void QQuickWindowPrivate::renderSceneGraph(const QSize &size)
         renderer->setViewportRect(QRect(QPoint(0, 0), size * devicePixelRatio));
     }
     renderer->setProjectionMatrixToRect(QRect(QPoint(0, 0), size));
-    renderer->setDevicePixelRatio(q->devicePixelRatio());
+    renderer->setDevicePixelRatio(devicePixelRatio);
 
     context->renderNextFrame(renderer, fboId);
     emit q->afterRendering();
@@ -3160,7 +3160,7 @@ QImage QQuickWindow::grabWindow()
         d->syncSceneGraph();
         d->renderSceneGraph(size());
 
-        QImage image = qt_gl_read_framebuffer(size() * devicePixelRatio(), false, false);
+        QImage image = qt_gl_read_framebuffer(size() * effectiveDevicePixelRatio(), false, false);
         d->cleanupNodesOnShutdown();
         d->context->invalidate();
         context.doneCurrent();
@@ -3923,6 +3923,23 @@ void QQuickWindow::runJobsAfterSwap()
     d->runAndClearJobs(&d->afterSwapJobs);
 }
 
+/*!
+ * Returns the device pixel ratio for this window.
+ *
+ * This is different from QWindow::devicePixelRatio() in that it supports
+ * redirected rendering via QQuickRenderControl. When using a
+ * QQuickRenderControl, the QQuickWindow is often not created, meaning it is
+ * never shown and there is no underlying native window created in the
+ * windowing system. As a result, querying properties like the device pixel
+ * ratio cannot give correct results. Use this function instead.
+ *
+ * \sa QWindow::devicePixelRatio()
+ */
+int QQuickWindow::effectiveDevicePixelRatio() const
+{
+    QWindow *w = QQuickRenderControl::renderWindowFor(const_cast<QQuickWindow *>(this));
+    return w ? w->devicePixelRatio() : devicePixelRatio();
+}
 
 #include "moc_qquickwindow.cpp"
 
diff --git a/src/quick/items/qquickwindow.h b/src/quick/items/qquickwindow.h
index b52d6b807e..3cac691963 100644
--- a/src/quick/items/qquickwindow.h
+++ b/src/quick/items/qquickwindow.h
@@ -142,6 +142,8 @@ public:
 
     void scheduleRenderJob(QRunnable *job, RenderStage schedule);
 
+    int effectiveDevicePixelRatio() const;
+
 Q_SIGNALS:
     void frameSwapped();
     Q_REVISION(2) void openglContextCreated(QOpenGLContext *context);