Bottlenecks when compositing widgets with RHI

diff --git a/src/client/qwaylandshmbackingstore.cpp b/src/client/qwaylandshmbackingstore.cpp
index 02d830ad..01b1a569 100644
--- a/src/client/qwaylandshmbackingstore.cpp
+++ b/src/client/qwaylandshmbackingstore.cpp
@@ -370,7 +370,12 @@ QImage QWaylandShmBackingStore::toImage() const
     // instead of flush() for widgets that have renderToTexture children
     // (QOpenGLWidget, QQuickWidget).

-    return *contentSurface();
+    QImage &image = *contentSurface();
+
+    // Return an image that does not share QImageData with the original image,
+    // even if they both point to the same data, otherwise painting to
+    // the image would detach it from the data.
+    return QImage(image.bits(), image.width(), image.height(), image.bytesPerLine(), image.format());
 }
 #endif  // opengl

diff --git a/src/gui/painting/qbackingstoredefaultcompositor.cpp b/src/gui/painting/qbackingstoredefaultcompositor.cpp
index 13a8bdb157..af5d88fe66 100644
--- a/src/gui/painting/qbackingstoredefaultcompositor.cpp
+++ b/src/gui/painting/qbackingstoredefaultcompositor.cpp
@@ -46,7 +46,7 @@ QRhiTexture *QBackingStoreDefaultCompositor::toTexture(const QPlatformBackingSto
     return toTexture(backingStore->toImage(), rhi, resourceUpdates, dirtyRegion, flags);
 }

-QRhiTexture *QBackingStoreDefaultCompositor::toTexture(const QImage &sourceImage,
+QRhiTexture *QBackingStoreDefaultCompositor::toTexture(QImage image,
                                                        QRhi *rhi,
                                                        QRhiResourceUpdateBatch *resourceUpdates,
                                                        const QRegion &dirtyRegion,
@@ -63,8 +63,6 @@ QRhiTexture *QBackingStoreDefaultCompositor::toTexture(const QImage &sourceImage
         return nullptr;
     }

-    QImage image = sourceImage;
-
     bool needsConversion = false;
     *flags = {};

@@ -515,7 +513,7 @@ QPlatformBackingStore::FlushResult QBackingStoreDefaultCompositor::flush(QPlatfo
             const QImage::Format format = QImage::toImageFormat(graphicsBuffer->format());
             const QSize size = graphicsBuffer->size();
             QImage wrapperImage(graphicsBuffer->data(), size.width(), size.height(), graphicsBuffer->bytesPerLine(), format);
-            toTexture(wrapperImage, rhi, resourceUpdates, scaledRegion(region, sourceDevicePixelRatio, offset), &flags);
+            toTexture(std::move(wrapperImage), rhi, resourceUpdates, scaledRegion(region, sourceDevicePixelRatio, offset), &flags);
             gotTextureFromGraphicsBuffer = true;
             graphicsBuffer->unlock();
             if (graphicsBuffer->origin() == QPlatformGraphicsBuffer::OriginBottomLeft)
diff --git a/src/gui/painting/qbackingstoredefaultcompositor_p.h b/src/gui/painting/qbackingstoredefaultcompositor_p.h
index 2f835e5d35..1ced8e4cdc 100644
--- a/src/gui/painting/qbackingstoredefaultcompositor_p.h
+++ b/src/gui/painting/qbackingstoredefaultcompositor_p.h
@@ -55,7 +55,7 @@ private:
     Q_DECLARE_FLAGS(UpdateQuadDataOptions, UpdateQuadDataOption)

     void ensureResources(QRhiSwapChain *swapchain, QRhiResourceUpdateBatch *resourceUpdates);
-    QRhiTexture *toTexture(const QImage &image,
+    QRhiTexture *toTexture(QImage image,
                            QRhi *rhi,
                            QRhiResourceUpdateBatch *resourceUpdates,
                            const QRegion &dirtyRegion,

diff --git a/src/plugins/platforms/xcb/qxcbbackingstore.cpp b/src/plugins/platforms/xcb/qxcbbackingstore.cpp
index 0659cf9fc4..9e4442af45 100644
--- a/src/plugins/platforms/xcb/qxcbbackingstore.cpp
+++ b/src/plugins/platforms/xcb/qxcbbackingstore.cpp
@@ -815,12 +815,12 @@ QImage QXcbBackingStore::toImage() const

     m_image->flushScrolledRegion(true);

-    QImage image = *m_image->image();
+    QImage &image = *m_image->image();

     // Return an image that does not share QImageData with the original image,
     // even if they both point to the same data of the m_xcb_image, otherwise
     // painting to m_qimage would detach it from the m_xcb_image data.
-    return QImage(image.constBits(), image.width(), image.height(), image.format());
+    return QImage(image.bits(), image.width(), image.height(), image.format());
 }

 QPlatformGraphicsBuffer *QXcbBackingStore::graphicsBuffer() const

diff --git a/src/gui/rhi/qrhigles2.cpp b/src/gui/rhi/qrhigles2.cpp
index 02138d7fb7..6d89b9d228 100644
--- a/src/gui/rhi/qrhigles2.cpp
+++ b/src/gui/rhi/qrhigles2.cpp
@@ -2224,13 +2224,21 @@ void QRhiGles2::enqueueSubresUpload(QGles2Texture *texD, QGles2CommandBuffer *cb
     if (!subresDesc.image().isNull()) {
         QImage img = subresDesc.image();
         QSize size = img.size();
+        static const int bytesPerPixel = 4;
+        const int strideInPixels = img.bytesPerLine() / bytesPerPixel;
+        const bool hasUnpackRowLength = !ctx->isOpenGLES() || ctx->format().majorVersion() >= 3;
         QGles2CommandBuffer::Command &cmd(cbD->commands.get());
         cmd.cmd = QGles2CommandBuffer::Command::SubImage;
         if (!subresDesc.sourceSize().isEmpty() || !subresDesc.sourceTopLeft().isNull()) {
             const QPoint sp = subresDesc.sourceTopLeft();
             if (!subresDesc.sourceSize().isEmpty())
                 size = subresDesc.sourceSize();
-            img = img.copy(sp.x(), sp.y(), size.width(), size.height());
+            if (hasUnpackRowLength || (strideInPixels == img.width() && size.width() == img.width())) {
+                const uchar *data = img.constBits() + ((sp.x() * img.depth()) >> 3) + sp.y() * img.bytesPerLine();
+                img = QImage(data, size.width(), size.height(), img.bytesPerLine(), img.format());
+            } else {
+                img = img.copy(sp.x(), sp.y(), size.width(), size.height());
+            }
         }
         cmd.args.subImage.target = texD->target;
         cmd.args.subImage.texture = texD->texture;
@@ -2244,7 +2252,7 @@ void QRhiGles2::enqueueSubresUpload(QGles2Texture *texD, QGles2CommandBuffer *cb
         cmd.args.subImage.glformat = texD->glformat;
         cmd.args.subImage.gltype = texD->gltype;
         cmd.args.subImage.rowStartAlign = 4;
-        cmd.args.subImage.rowLength = 0;
+        cmd.args.subImage.rowLength = hasUnpackRowLength ? strideInPixels : 0;
         cmd.args.subImage.data = cbD->retainImage(img);
     } else if (!rawData.isEmpty() && isCompressed) {
         const int depth = qMax(1, texD->m_depth);