rhi: Execute pending host writes on nativeBuffer() query

Otherwise it is impossible to write an application that pulls out the
VkBuffer for a Dynamic QRhiBuffer, and then uses it with custom Vulkan
operations that read from the buffer. More precisely, the problem arises
only if the buffer in question is not used in combination with any QRhi
operations, because in that case there is nothing that would trigger
doing the host writes queued up by a resource batch's updateDynamicBuffer().

Task-number: QTBUG-82435
Change-Id: Ieb54422f1493921bc6d4d029be56130cd3a1362a
Reviewed-by: Christian Strømme <christian.stromme@qt.io>

1 files changed, 8 insertions, 4 deletions

diff --git a/src/gui/rhi/qrhid3d11.cpp b/src/gui/rhi/qrhid3d11.cpp
index f7c7f4a9f2..ce39b42cf5 100644
--- a/src/gui/rhi/qrhid3d11.cpp
+++ b/src/gui/rhi/qrhid3d11.cpp
@@ -608,7 +608,7 @@ void QRhiD3D11::setShaderResources(QRhiCommandBuffer *cb, QRhiShaderResourceBind
         {
             QD3D11Buffer *bufD = QRHI_RES(QD3D11Buffer, b->u.ubuf.buf);
             if (bufD->m_type == QRhiBuffer::Dynamic)
-                executeBufferHostWritesForCurrentFrame(bufD);
+                executeBufferHostWrites(bufD);
 
             if (bufD->generation != bd.ubuf.generation || bufD->m_id != bd.ubuf.id) {
                 srbUpdate = true;
@@ -725,7 +725,7 @@ void QRhiD3D11::setVertexInput(QRhiCommandBuffer *cb,
         QD3D11Buffer *bufD = QRHI_RES(QD3D11Buffer, bindings[i].first);
         Q_ASSERT(bufD->m_usage.testFlag(QRhiBuffer::VertexBuffer));
         if (bufD->m_type == QRhiBuffer::Dynamic)
-            executeBufferHostWritesForCurrentFrame(bufD);
+            executeBufferHostWrites(bufD);
 
         if (cbD->currentVertexBuffers[inputSlot] != bufD->buffer
                 || cbD->currentVertexOffsets[inputSlot] != bindings[i].second)
@@ -757,7 +757,7 @@ void QRhiD3D11::setVertexInput(QRhiCommandBuffer *cb,
         QD3D11Buffer *ibufD = QRHI_RES(QD3D11Buffer, indexBuf);
         Q_ASSERT(ibufD->m_usage.testFlag(QRhiBuffer::IndexBuffer));
         if (ibufD->m_type == QRhiBuffer::Dynamic)
-            executeBufferHostWritesForCurrentFrame(ibufD);
+            executeBufferHostWrites(ibufD);
 
         const DXGI_FORMAT dxgiFormat = indexFormat == QRhiCommandBuffer::IndexUInt16 ? DXGI_FORMAT_R16_UINT
                                                                                      : DXGI_FORMAT_R32_UINT;
@@ -1920,7 +1920,7 @@ void QRhiD3D11::updateShaderResourceBindings(QD3D11ShaderResourceBindings *srbD)
     srbD->csUAVs.finish();
 }
 
-void QRhiD3D11::executeBufferHostWritesForCurrentFrame(QD3D11Buffer *bufD)
+void QRhiD3D11::executeBufferHostWrites(QD3D11Buffer *bufD)
 {
     if (!bufD->hasPendingDynamicUpdates)
         return;
@@ -2388,6 +2388,10 @@ bool QD3D11Buffer::build()
 
 QRhiBuffer::NativeBuffer QD3D11Buffer::nativeBuffer()
 {
+    if (m_type == Dynamic) {
+        QRHI_RES_RHI(QRhiD3D11);
+        rhiD->executeBufferHostWrites(this);
+    }
     return { { &buffer }, 1 };
 }