rhi: Make it possible to clone a QRhiRenderPassDescriptor

Pick-to: 6.1
Task-number: QTBUG-91888
Change-Id: Ib6d2e639e6c24f3e9a733c6563dc8a6d6da47719
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

13 files changed, 191 insertions, 64 deletions

diff --git a/src/gui/rhi/qrhi.cpp b/src/gui/rhi/qrhi.cpp
index 8d3c56da53..db85730040 100644
--- a/src/gui/rhi/qrhi.cpp
+++ b/src/gui/rhi/qrhi.cpp
@@ -158,10 +158,12 @@ Q_LOGGING_CATEGORY(QRHI_LOG_INFO, "qt.rhi.general")
     native resources. That is only done when calling the \c create() function of a
     subclass, for example, QRhiBuffer::create() or QRhiTexture::create().
 
-    \li The exception is
-    QRhiTextureRenderTarget::newCompatibleRenderPassDescriptor() and
-    QRhiSwapChain::newCompatibleRenderPassDescriptor(). There is no \c create()
-    operation for these and the returned object is immediately active.
+    \li The exceptions are
+    QRhiTextureRenderTarget::newCompatibleRenderPassDescriptor(),
+    QRhiSwapChain::newCompatibleRenderPassDescriptor(), and
+    QRhiRenderPassDescriptor::newCompatibleRenderPassDescriptor(). There is no
+    \c create() operation for these and the returned object is immediately
+    active.
 
     \li The resource objects themselves are treated as immutable: once a
     resource has create() called, changing any parameters via the setters, such as,
@@ -2605,7 +2607,7 @@ QRhiResource::Type QRhiRenderPassDescriptor::resourceType() const
 }
 
 /*!
-    \fn bool QRhiRenderPassDescriptor::isCompatible(const QRhiRenderPassDescriptor *other) const;
+    \fn bool QRhiRenderPassDescriptor::isCompatible(const QRhiRenderPassDescriptor *other) const
 
     \return true if the \a other QRhiRenderPassDescriptor is compatible with
     this one, meaning \c this and \a other can be used interchangebly in
@@ -2620,6 +2622,34 @@ QRhiResource::Type QRhiRenderPassDescriptor::resourceType() const
     allowing a different QRhiRenderPassDescriptor and
     QRhiShaderResourceBindings to be used in combination with the pipeline, as
     long as they are compatible.
+
+    The exact details of compatibility depend on the underlying graphics API.
+    Two renderpass descriptors
+    \l{QRhiTextureRenderTarget::newCompatibleRenderPassDescriptor()}{created}
+    from the same QRhiTextureRenderTarget are always compatible.
+
+    \sa newCompatibleRenderPassDescriptor()
+ */
+
+/*!
+    \fn QRhiRenderPassDescriptor *QRhiRenderPassDescriptor::newCompatibleRenderPassDescriptor() const
+
+    \return a new QRhiRenderPassDescriptor that is
+    \l{isCompatible()}{compatible} with this one.
+
+    This function allows cloning a QRhiRenderPassDescriptor. The returned
+    object is ready to be used, and the ownership is transferred to the caller.
+    Cloning a QRhiRenderPassDescriptor object can become useful in situations
+    where the object is stored in data structures related to graphics pipelines
+    (in order to allow creating new pipelines which in turn requires a
+    renderpass descriptor object), and the lifetime of the renderpass
+    descriptor created from a render target may be shorter than the pipelines.
+    (for example, because the engine manages and destroys renderpasses together
+    with the textures and render targets it was created from) In such a
+    situation, it can be beneficial to store a cloned version in the data
+    structures, and thus transferring ownership as well.
+
+    \sa isCompatible()
  */
 
 /*!
diff --git a/src/gui/rhi/qrhi_p.h b/src/gui/rhi/qrhi_p.h
index f3255eca5b..e0afabc73a 100644
--- a/src/gui/rhi/qrhi_p.h
+++ b/src/gui/rhi/qrhi_p.h
@@ -951,6 +951,8 @@ public:
     virtual bool isCompatible(const QRhiRenderPassDescriptor *other) const = 0;
     virtual const QRhiNativeHandles *nativeHandles();
 
+    virtual QRhiRenderPassDescriptor *newCompatibleRenderPassDescriptor() const = 0;
+
 protected:
     QRhiRenderPassDescriptor(QRhiImplementation *rhi);
 };
diff --git a/src/gui/rhi/qrhid3d11.cpp b/src/gui/rhi/qrhid3d11.cpp
index fef911c22a..3e0ba0820b 100644
--- a/src/gui/rhi/qrhid3d11.cpp
+++ b/src/gui/rhi/qrhid3d11.cpp
@@ -3281,6 +3281,11 @@ bool QD3D11RenderPassDescriptor::isCompatible(const QRhiRenderPassDescriptor *ot
     return true;
 }
 
+QRhiRenderPassDescriptor *QD3D11RenderPassDescriptor::newCompatibleRenderPassDescriptor() const
+{
+    return new QD3D11RenderPassDescriptor(m_rhi);
+}
+
 QD3D11ReferenceRenderTarget::QD3D11ReferenceRenderTarget(QRhiImplementation *rhi)
     : QRhiRenderTarget(rhi),
       d(rhi)
diff --git a/src/gui/rhi/qrhid3d11_p_p.h b/src/gui/rhi/qrhid3d11_p_p.h
index 5eb866119f..82cbe5114c 100644
--- a/src/gui/rhi/qrhid3d11_p_p.h
+++ b/src/gui/rhi/qrhid3d11_p_p.h
@@ -143,6 +143,7 @@ struct QD3D11RenderPassDescriptor : public QRhiRenderPassDescriptor
     ~QD3D11RenderPassDescriptor();
     void destroy() override;
     bool isCompatible(const QRhiRenderPassDescriptor *other) const override;
+    QRhiRenderPassDescriptor *newCompatibleRenderPassDescriptor() const override;
 };
 
 struct QD3D11RenderTargetData
diff --git a/src/gui/rhi/qrhigles2.cpp b/src/gui/rhi/qrhigles2.cpp
index 1556e45fbf..e3895897e9 100644
--- a/src/gui/rhi/qrhigles2.cpp
+++ b/src/gui/rhi/qrhigles2.cpp
@@ -4549,6 +4549,11 @@ bool QGles2RenderPassDescriptor::isCompatible(const QRhiRenderPassDescriptor *ot
     return true;
 }
 
+QRhiRenderPassDescriptor *QGles2RenderPassDescriptor::newCompatibleRenderPassDescriptor() const
+{
+    return new QGles2RenderPassDescriptor(m_rhi);
+}
+
 QGles2ReferenceRenderTarget::QGles2ReferenceRenderTarget(QRhiImplementation *rhi)
     : QRhiRenderTarget(rhi),
       d(rhi)
diff --git a/src/gui/rhi/qrhigles2_p_p.h b/src/gui/rhi/qrhigles2_p_p.h
index 98f2f98b8a..d30fd89545 100644
--- a/src/gui/rhi/qrhigles2_p_p.h
+++ b/src/gui/rhi/qrhigles2_p_p.h
@@ -193,6 +193,7 @@ struct QGles2RenderPassDescriptor : public QRhiRenderPassDescriptor
     ~QGles2RenderPassDescriptor();
     void destroy() override;
     bool isCompatible(const QRhiRenderPassDescriptor *other) const override;
+    QRhiRenderPassDescriptor *newCompatibleRenderPassDescriptor() const override;
 };
 
 struct QGles2RenderTargetData
diff --git a/src/gui/rhi/qrhimetal.mm b/src/gui/rhi/qrhimetal.mm
index a736dd511e..ddbd0ea740 100644
--- a/src/gui/rhi/qrhimetal.mm
+++ b/src/gui/rhi/qrhimetal.mm
@@ -2900,6 +2900,16 @@ bool QMetalRenderPassDescriptor::isCompatible(const QRhiRenderPassDescriptor *ot
     return true;
 }
 
+QRhiRenderPassDescriptor *QMetalRenderPassDescriptor::newCompatibleRenderPassDescriptor() const
+{
+    QMetalRenderPassDescriptor *rp = new QMetalRenderPassDescriptor(m_rhi);
+    rp->colorAttachmentCount = colorAttachmentCount;
+    rp->hasDepthStencil = hasDepthStencil;
+    memcpy(rp->colorFormat, colorFormat, sizeof(colorFormat));
+    rp->dsFormat = dsFormat;
+    return rp;
+}
+
 QMetalReferenceRenderTarget::QMetalReferenceRenderTarget(QRhiImplementation *rhi)
     : QRhiRenderTarget(rhi),
       d(new QMetalRenderTargetData)
diff --git a/src/gui/rhi/qrhimetal_p_p.h b/src/gui/rhi/qrhimetal_p_p.h
index 4971ecc18c..c8ba5940a8 100644
--- a/src/gui/rhi/qrhimetal_p_p.h
+++ b/src/gui/rhi/qrhimetal_p_p.h
@@ -145,6 +145,7 @@ struct QMetalRenderPassDescriptor : public QRhiRenderPassDescriptor
     ~QMetalRenderPassDescriptor();
     void destroy() override;
     bool isCompatible(const QRhiRenderPassDescriptor *other) const override;
+    QRhiRenderPassDescriptor *newCompatibleRenderPassDescriptor() const override;
 
     // there is no MTLRenderPassDescriptor here as one will be created for each pass in beginPass()
 
diff --git a/src/gui/rhi/qrhinull.cpp b/src/gui/rhi/qrhinull.cpp
index 32ba27fcf8..29f3bab8b0 100644
--- a/src/gui/rhi/qrhinull.cpp
+++ b/src/gui/rhi/qrhinull.cpp
@@ -733,6 +733,11 @@ bool QNullRenderPassDescriptor::isCompatible(const QRhiRenderPassDescriptor *oth
     return true;
 }
 
+QRhiRenderPassDescriptor *QNullRenderPassDescriptor::newCompatibleRenderPassDescriptor() const
+{
+    return new QNullRenderPassDescriptor(m_rhi);
+}
+
 QNullReferenceRenderTarget::QNullReferenceRenderTarget(QRhiImplementation *rhi)
     : QRhiRenderTarget(rhi),
       d(rhi)
diff --git a/src/gui/rhi/qrhinull_p_p.h b/src/gui/rhi/qrhinull_p_p.h
index 273aee9c3e..d296c0bbf0 100644
--- a/src/gui/rhi/qrhinull_p_p.h
+++ b/src/gui/rhi/qrhinull_p_p.h
@@ -105,6 +105,7 @@ struct QNullRenderPassDescriptor : public QRhiRenderPassDescriptor
     ~QNullRenderPassDescriptor();
     void destroy() override;
     bool isCompatible(const QRhiRenderPassDescriptor *other) const override;
+    QRhiRenderPassDescriptor *newCompatibleRenderPassDescriptor() const override;
 };
 
 struct QNullRenderTargetData
diff --git a/src/gui/rhi/qrhivulkan.cpp b/src/gui/rhi/qrhivulkan.cpp
index 34b81671ca..3d5048df1c 100644
--- a/src/gui/rhi/qrhivulkan.cpp
+++ b/src/gui/rhi/qrhivulkan.cpp
@@ -1174,6 +1174,28 @@ VkFormat QRhiVulkan::optimalDepthStencilFormat()
     return optimalDsFormat;
 }
 
+static void fillRenderPassCreateInfo(VkRenderPassCreateInfo *rpInfo,
+                                     VkSubpassDescription *subpassDesc,
+                                     QVkRenderPassDescriptor *rpD)
+{
+    memset(subpassDesc, 0, sizeof(VkSubpassDescription));
+    subpassDesc->pipelineBindPoint = VK_PIPELINE_BIND_POINT_GRAPHICS;
+    subpassDesc->colorAttachmentCount = uint32_t(rpD->colorRefs.count());
+    Q_ASSERT(rpD->colorRefs.count() == rpD->resolveRefs.count());
+    subpassDesc->pColorAttachments = !rpD->colorRefs.isEmpty() ? rpD->colorRefs.constData() : nullptr;
+    subpassDesc->pDepthStencilAttachment = rpD->hasDepthStencil ? &rpD->dsRef : nullptr;
+    subpassDesc->pResolveAttachments = !rpD->resolveRefs.isEmpty() ? rpD->resolveRefs.constData() : nullptr;
+
+    memset(rpInfo, 0, sizeof(VkRenderPassCreateInfo));
+    rpInfo->sType = VK_STRUCTURE_TYPE_RENDER_PASS_CREATE_INFO;
+    rpInfo->attachmentCount = uint32_t(rpD->attDescs.count());
+    rpInfo->pAttachments = rpD->attDescs.constData();
+    rpInfo->subpassCount = 1;
+    rpInfo->pSubpasses = subpassDesc;
+    rpInfo->dependencyCount = uint32_t(rpD->subpassDeps.count());
+    rpInfo->pDependencies = !rpD->subpassDeps.isEmpty() ? rpD->subpassDeps.constData() : nullptr;
+}
+
 bool QRhiVulkan::createDefaultRenderPass(QVkRenderPassDescriptor *rpD, bool hasDepthStencil, VkSampleCountFlagBits samples, VkFormat colorFormat)
 {
     // attachment list layout is color (1), ds (0-1), resolve (0-1)
@@ -1192,6 +1214,8 @@ bool QRhiVulkan::createDefaultRenderPass(QVkRenderPassDescriptor *rpD, bool hasD
 
     rpD->colorRefs.append({ 0, VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL });
 
+    rpD->hasDepthStencil = hasDepthStencil;
+
     if (hasDepthStencil) {
         // clear on load + no store + lazy alloc + transient image should play
         // nicely with tiled GPUs (no physical backing necessary for ds buffer)
@@ -1224,53 +1248,33 @@ bool QRhiVulkan::createDefaultRenderPass(QVkRenderPassDescriptor *rpD, bool hasD
         rpD->resolveRefs.append({ 2, VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL });
     }
 
-    VkSubpassDescription subpassDesc;
-    memset(&subpassDesc, 0, sizeof(subpassDesc));
-    subpassDesc.pipelineBindPoint = VK_PIPELINE_BIND_POINT_GRAPHICS;
-    subpassDesc.colorAttachmentCount = 1;
-    subpassDesc.pColorAttachments = rpD->colorRefs.constData();
-    subpassDesc.pDepthStencilAttachment = hasDepthStencil ? &rpD->dsRef : nullptr;
-
     // Replace the first implicit dep (TOP_OF_PIPE / ALL_COMMANDS) with our own.
-    VkSubpassDependency subpassDeps[2];
-    memset(subpassDeps, 0, sizeof(subpassDeps));
-    subpassDeps[0].srcSubpass = VK_SUBPASS_EXTERNAL;
-    subpassDeps[0].dstSubpass = 0;
-    subpassDeps[0].srcStageMask = VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT;
-    subpassDeps[0].dstStageMask = VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT;
-    subpassDeps[0].srcAccessMask = 0;
-    subpassDeps[0].dstAccessMask = VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT;
+    VkSubpassDependency subpassDep;
+    memset(&subpassDep, 0, sizeof(subpassDep));
+    subpassDep.srcSubpass = VK_SUBPASS_EXTERNAL;
+    subpassDep.dstSubpass = 0;
+    subpassDep.srcStageMask = VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT;
+    subpassDep.dstStageMask = VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT;
+    subpassDep.srcAccessMask = 0;
+    subpassDep.dstAccessMask = VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT;
+    rpD->subpassDeps.append(subpassDep);
     if (hasDepthStencil) {
-        subpassDeps[1].srcSubpass = VK_SUBPASS_EXTERNAL;
-        subpassDeps[1].dstSubpass = 0;
-        subpassDeps[1].srcStageMask = VK_PIPELINE_STAGE_EARLY_FRAGMENT_TESTS_BIT
+        memset(&subpassDep, 0, sizeof(subpassDep));
+        subpassDep.srcSubpass = VK_SUBPASS_EXTERNAL;
+        subpassDep.dstSubpass = 0;
+        subpassDep.srcStageMask = VK_PIPELINE_STAGE_EARLY_FRAGMENT_TESTS_BIT
             | VK_PIPELINE_STAGE_LATE_FRAGMENT_TESTS_BIT;
-        subpassDeps[1].dstStageMask = VK_PIPELINE_STAGE_EARLY_FRAGMENT_TESTS_BIT
+        subpassDep.dstStageMask = VK_PIPELINE_STAGE_EARLY_FRAGMENT_TESTS_BIT
             | VK_PIPELINE_STAGE_LATE_FRAGMENT_TESTS_BIT;
-        subpassDeps[1].srcAccessMask = VK_ACCESS_DEPTH_STENCIL_ATTACHMENT_WRITE_BIT;
-        subpassDeps[1].dstAccessMask = VK_ACCESS_DEPTH_STENCIL_ATTACHMENT_READ_BIT
+        subpassDep.srcAccessMask = VK_ACCESS_DEPTH_STENCIL_ATTACHMENT_WRITE_BIT;
+        subpassDep.dstAccessMask = VK_ACCESS_DEPTH_STENCIL_ATTACHMENT_READ_BIT
             | VK_ACCESS_DEPTH_STENCIL_ATTACHMENT_WRITE_BIT;
+        rpD->subpassDeps.append(subpassDep);
     }
 
     VkRenderPassCreateInfo rpInfo;
-    memset(&rpInfo, 0, sizeof(rpInfo));
-    rpInfo.sType = VK_STRUCTURE_TYPE_RENDER_PASS_CREATE_INFO;
-    rpInfo.attachmentCount = 1;
-    rpInfo.pAttachments = rpD->attDescs.constData();
-    rpInfo.subpassCount = 1;
-    rpInfo.pSubpasses = &subpassDesc;
-    rpInfo.dependencyCount = 1;
-    rpInfo.pDependencies = subpassDeps;
-
-    if (hasDepthStencil) {
-        rpInfo.attachmentCount += 1;
-        rpInfo.dependencyCount += 1;
-    }
-
-    if (samples > VK_SAMPLE_COUNT_1_BIT) {
-        rpInfo.attachmentCount += 1;
-        subpassDesc.pResolveAttachments = rpD->resolveRefs.constData();
-    }
+    VkSubpassDescription subpassDesc;
+    fillRenderPassCreateInfo(&rpInfo, &subpassDesc, rpD);
 
     VkResult err = df->vkCreateRenderPass(dev, &rpInfo, nullptr, &rpD->rp);
     if (err != VK_SUCCESS) {
@@ -1278,8 +1282,6 @@ bool QRhiVulkan::createDefaultRenderPass(QVkRenderPassDescriptor *rpD, bool hasD
         return false;
     }
 
-    rpD->hasDepthStencil = hasDepthStencil;
-
     return true;
 }
 
@@ -1377,25 +1379,14 @@ bool QRhiVulkan::createOffscreenRenderPass(QVkRenderPassDescriptor *rpD,
         }
     }
 
-    VkSubpassDescription subpassDesc;
-    memset(&subpassDesc, 0, sizeof(subpassDesc));
-    subpassDesc.pipelineBindPoint = VK_PIPELINE_BIND_POINT_GRAPHICS;
-    subpassDesc.colorAttachmentCount = uint32_t(rpD->colorRefs.count());
-    Q_ASSERT(rpD->colorRefs.count() == rpD->resolveRefs.count());
-    subpassDesc.pColorAttachments = !rpD->colorRefs.isEmpty() ? rpD->colorRefs.constData() : nullptr;
-    subpassDesc.pDepthStencilAttachment = rpD->hasDepthStencil ? &rpD->dsRef : nullptr;
-    subpassDesc.pResolveAttachments = !rpD->resolveRefs.isEmpty() ? rpD->resolveRefs.constData() : nullptr;
+    // rpD->subpassDeps stays empty: don't yet know the correct initial/final
+    // access and stage stuff for the implicit deps at this point, so leave it
+    // to the resource tracking and activateTextureRenderTarget() to generate
+    // barriers.
 
     VkRenderPassCreateInfo rpInfo;
-    memset(&rpInfo, 0, sizeof(rpInfo));
-    rpInfo.sType = VK_STRUCTURE_TYPE_RENDER_PASS_CREATE_INFO;
-    rpInfo.attachmentCount = uint32_t(rpD->attDescs.count());
-    rpInfo.pAttachments = rpD->attDescs.constData();
-    rpInfo.subpassCount = 1;
-    rpInfo.pSubpasses = &subpassDesc;
-    // don't yet know the correct initial/final access and stage stuff for the
-    // implicit deps at this point, so leave it to the resource tracking and
-    // activateTextureRenderTarget() to generate barriers
+    VkSubpassDescription subpassDesc;
+    fillRenderPassCreateInfo(&rpInfo, &subpassDesc, rpD);
 
     VkResult err = df->vkCreateRenderPass(dev, &rpInfo, nullptr, &rpD->rp);
     if (err != VK_SUCCESS) {
@@ -6149,9 +6140,39 @@ bool QVkRenderPassDescriptor::isCompatible(const QRhiRenderPassDescriptor *other
             return false;
     }
 
+    // subpassDeps is not included
+
     return true;
 }
 
+QRhiRenderPassDescriptor *QVkRenderPassDescriptor::newCompatibleRenderPassDescriptor() const
+{
+    QVkRenderPassDescriptor *rpD = new QVkRenderPassDescriptor(m_rhi);
+
+    rpD->ownsRp = true;
+    rpD->attDescs = attDescs;
+    rpD->colorRefs = colorRefs;
+    rpD->resolveRefs = resolveRefs;
+    rpD->subpassDeps = subpassDeps;
+    rpD->hasDepthStencil = hasDepthStencil;
+    rpD->dsRef = dsRef;
+
+    VkRenderPassCreateInfo rpInfo;
+    VkSubpassDescription subpassDesc;
+    fillRenderPassCreateInfo(&rpInfo, &subpassDesc, rpD);
+
+    QRHI_RES_RHI(QRhiVulkan);
+    VkResult err = rhiD->df->vkCreateRenderPass(rhiD->dev, &rpInfo, nullptr, &rpD->rp);
+    if (err != VK_SUCCESS) {
+        qWarning("Failed to create renderpass: %d", err);
+        delete rpD;
+        return nullptr;
+    }
+
+    rhiD->registerResource(rpD);
+    return rpD;
+}
+
 const QRhiNativeHandles *QVkRenderPassDescriptor::nativeHandles()
 {
     nativeHandlesStruct.renderPass = rp;
diff --git a/src/gui/rhi/qrhivulkan_p_p.h b/src/gui/rhi/qrhivulkan_p_p.h
index f54439b5f2..bb60fca42a 100644
--- a/src/gui/rhi/qrhivulkan_p_p.h
+++ b/src/gui/rhi/qrhivulkan_p_p.h
@@ -185,6 +185,7 @@ struct QVkRenderPassDescriptor : public QRhiRenderPassDescriptor
     ~QVkRenderPassDescriptor();
     void destroy() override;
     bool isCompatible(const QRhiRenderPassDescriptor *other) const override;
+    QRhiRenderPassDescriptor *newCompatibleRenderPassDescriptor() const override;
     const QRhiNativeHandles *nativeHandles() override;
 
     VkRenderPass rp = VK_NULL_HANDLE;
@@ -192,6 +193,7 @@ struct QVkRenderPassDescriptor : public QRhiRenderPassDescriptor
     QVarLengthArray<VkAttachmentDescription, 8> attDescs;
     QVarLengthArray<VkAttachmentReference, 8> colorRefs;
     QVarLengthArray<VkAttachmentReference, 8> resolveRefs;
+    QVarLengthArray<VkSubpassDependency, 2> subpassDeps;
     bool hasDepthStencil = false;
     VkAttachmentReference dsRef;
     QRhiVulkanRenderPassNativeHandles nativeHandlesStruct;
diff --git a/tests/auto/gui/rhi/qrhi/tst_qrhi.cpp b/tests/auto/gui/rhi/qrhi/tst_qrhi.cpp
index ccb5f8a783..c4d1dca1bb 100644
--- a/tests/auto/gui/rhi/qrhi/tst_qrhi.cpp
+++ b/tests/auto/gui/rhi/qrhi/tst_qrhi.cpp
@@ -97,6 +97,8 @@ private slots:
     void srbWithNoResource();
     void renderPassDescriptorCompatibility_data();
     void renderPassDescriptorCompatibility();
+    void renderPassDescriptorClone_data();
+    void renderPassDescriptorClone();
 
     void renderToTextureSimple_data();
     void renderToTextureSimple();
@@ -3361,7 +3363,7 @@ void tst_QRhi::renderPassDescriptorCompatibility()
 
     QScopedPointer<QRhi> rhi(QRhi::create(impl, initParams, QRhi::Flags(), nullptr));
     if (!rhi)
-        QSKIP("QRhi could not be created, skipping testing texture resource updates");
+        QSKIP("QRhi could not be created, skipping testing renderpass descriptors");
 
     // Note that checking compatibility is only relevant with backends where
     // there is a concept of renderpass descriptions (Vulkan, and partially
@@ -3511,6 +3513,47 @@ void tst_QRhi::renderPassDescriptorCompatibility()
     }
 }
 
+void tst_QRhi::renderPassDescriptorClone_data()
+{
+    rhiTestData();
+}
+
+void tst_QRhi::renderPassDescriptorClone()
+{
+    QFETCH(QRhi::Implementation, impl);
+    QFETCH(QRhiInitParams *, initParams);
+
+    QScopedPointer<QRhi> rhi(QRhi::create(impl, initParams, QRhi::Flags(), nullptr));
+    if (!rhi)
+        QSKIP("QRhi could not be created, skipping testing renderpass descriptors");
+
+    // tex and tex2 have the same format
+    QScopedPointer<QRhiTexture> tex(rhi->newTexture(QRhiTexture::RGBA8, QSize(512, 512), 1, QRhiTexture::RenderTarget));
+    QVERIFY(tex->create());
+    QScopedPointer<QRhiTexture> tex2(rhi->newTexture(QRhiTexture::RGBA8, QSize(512, 512), 1, QRhiTexture::RenderTarget));
+    QVERIFY(tex2->create());
+
+    QScopedPointer<QRhiRenderBuffer> ds(rhi->newRenderBuffer(QRhiRenderBuffer::DepthStencil, QSize(512, 512)));
+    QVERIFY(ds->create());
+
+    QScopedPointer<QRhiTextureRenderTarget> rt(rhi->newTextureRenderTarget({ tex.data() }));
+    QScopedPointer<QRhiRenderPassDescriptor> rpDesc(rt->newCompatibleRenderPassDescriptor());
+    rt->setRenderPassDescriptor(rpDesc.data());
+    QVERIFY(rt->create());
+
+    QScopedPointer<QRhiRenderPassDescriptor> rpDescClone(rpDesc->newCompatibleRenderPassDescriptor());
+    QVERIFY(rpDescClone);
+    QVERIFY(rpDesc->isCompatible(rpDescClone.data()));
+
+    // rt and rt2 have the same set of attachments
+    QScopedPointer<QRhiTextureRenderTarget> rt2(rhi->newTextureRenderTarget({ tex2.data() }));
+    QScopedPointer<QRhiRenderPassDescriptor> rpDesc2(rt2->newCompatibleRenderPassDescriptor());
+    rt2->setRenderPassDescriptor(rpDesc2.data());
+    QVERIFY(rt2->create());
+
+    QVERIFY(rpDesc2->isCompatible(rpDescClone.data()));
+}
+
 void tst_QRhi::pipelineCache_data()
 {
     rhiTestData();