Have a depth buffer when doing the heavy offscreen readback

The opaque pass will rely on it (by default at least). Not having
a depth buffer will almost certainly lead to rendering errors,
albeit silently since technically it's not an error not to have one.
Just make sure there is one.

The assumption is that the Z order problem mentioned in the comments
in the referenced bug is caused by this.

Task-number: QTBUG-87399
Change-Id: Ifbf5564848f17e7ce3498190d663c1ec693e86c9
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

1 files changed, 8 insertions, 1 deletions

diff --git a/src/quick/scenegraph/qsgrhisupport.cpp b/src/quick/scenegraph/qsgrhisupport.cpp
index 6a66906ca1..8a7274f947 100644
--- a/src/quick/scenegraph/qsgrhisupport.cpp
+++ b/src/quick/scenegraph/qsgrhisupport.cpp
@@ -741,7 +741,14 @@ QImage QSGRhiSupport::grabOffscreen(QQuickWindow *window)
         qWarning("Failed to build texture for offscreen readback");
         return QImage();
     }
-    QScopedPointer<QRhiTextureRenderTarget> rt(rhi->newTextureRenderTarget({ texture.data() }));
+    QScopedPointer<QRhiRenderBuffer> depthStencil(rhi->newRenderBuffer(QRhiRenderBuffer::DepthStencil, pixelSize, 1));
+    if (!depthStencil->create()) {
+        qWarning("Failed to create depth/stencil buffer for offscreen readback");
+        return QImage();
+    }
+    QRhiTextureRenderTargetDescription rtDesc(texture.data());
+    rtDesc.setDepthStencilBuffer(depthStencil.data());
+    QScopedPointer<QRhiTextureRenderTarget> rt(rhi->newTextureRenderTarget(rtDesc));
     QScopedPointer<QRhiRenderPassDescriptor> rpDesc(rt->newCompatibleRenderPassDescriptor());
     rt->setRenderPassDescriptor(rpDesc.data());
     if (!rt->create()) {