Introduce QRhi::nativeHandles() and texture import/export

Implement texture stuff for Metal for now, and exercise
it in texuploads.

examples/rhi/imguidemo/qrhiimgui.cpp

@@ -248,7 +248,6 @@ bool QRhiImgui::prepareFrame(QRhiRenderTarget *rt, QRhiRenderPassDescriptor *rp,
 
 void QRhiImgui::queueFrame(QRhiCommandBuffer *cb)
 {
-    ImGuiIO &io(ImGui::GetIO());
     ImDrawData *draw = ImGui::GetDrawData();
     cb->setViewport({ 0, 0, float(d->lastOutputSize.width()), float(d->lastOutputSize.height()) });
 

examples/rhi/texuploads/texuploads.cpp

@@ -59,25 +59,30 @@ struct {
     QRhiSampler *sampler = nullptr;
     QRhiShaderResourceBindings *srb = nullptr;
     QRhiGraphicsPipeline *ps = nullptr;
+    QVector<QRhiResource *> releasePool;
 
     float rotation = 0;
     QRhiResourceUpdateBatch *initialUpdates = nullptr;
     int frameCount = 0;
     QImage customImage;
     QRhiTexture *newTex = nullptr;
+    QRhiTexture *importedTex = nullptr;
     int testStage = 0;
 } d;
 
 void Window::customInit()
 {
     d.vbuf = m_r->newBuffer(QRhiBuffer::Immutable, QRhiBuffer::VertexBuffer, sizeof(cube));
+    d.releasePool << d.vbuf;
     d.vbuf->build();
 
     d.ubuf = m_r->newBuffer(QRhiBuffer::Dynamic, QRhiBuffer::UniformBuffer, 68);
+    d.releasePool << d.ubuf;
     d.ubuf->build();
 
     QImage baseImage(QLatin1String(":/qt256.png"));
     d.tex = m_r->newTexture(QRhiTexture::RGBA8, baseImage.size(), 1, QRhiTexture::UsedAsTransferSource);
+    d.releasePool << d.tex;
     d.tex->build();
 
     // As an alternative to what some of the other examples do, prepare an
@@ -90,9 +95,11 @@ void Window::customInit()
 
     d.sampler = m_r->newSampler(QRhiSampler::Linear, QRhiSampler::Linear, QRhiSampler::None,
                                 QRhiSampler::ClampToEdge, QRhiSampler::ClampToEdge);
+    d.releasePool << d.sampler;
     d.sampler->build();
 
     d.srb = m_r->newShaderResourceBindings();
+    d.releasePool << d.srb;
     d.srb->setBindings({
         QRhiShaderResourceBinding::uniformBuffer(0, QRhiShaderResourceBinding::VertexStage | QRhiShaderResourceBinding::FragmentStage, d.ubuf),
         QRhiShaderResourceBinding::sampledTexture(1, QRhiShaderResourceBinding::FragmentStage, d.tex, d.sampler)
@@ -100,6 +107,7 @@ void Window::customInit()
     d.srb->build();
 
     d.ps = m_r->newGraphicsPipeline();
+    d.releasePool << d.ps;
 
     d.ps->setDepthTest(true);
     d.ps->setDepthWrite(true);
@@ -147,40 +155,10 @@ void Window::customInit()
 
 void Window::customRelease()
 {
-    if (d.ps) {
-        d.ps->releaseAndDestroy();
-        d.ps = nullptr;
-    }
-
-    if (d.srb) {
-        d.srb->releaseAndDestroy();
-        d.srb = nullptr;
-    }
-
-    if (d.ubuf) {
-        d.ubuf->releaseAndDestroy();
-        d.ubuf = nullptr;
-    }
-
-    if (d.vbuf) {
-        d.vbuf->releaseAndDestroy();
-        d.vbuf = nullptr;
-    }
+    for (QRhiResource *r : d.releasePool)
+        r->releaseAndDestroy();
 
-    if (d.sampler) {
-        d.sampler->releaseAndDestroy();
-        d.sampler = nullptr;
-    }
-
-    if (d.tex) {
-        d.tex->releaseAndDestroy();
-        d.tex = nullptr;
-    }
-
-    if (d.newTex) {
-        d.newTex->releaseAndDestroy();
-        d.newTex = nullptr;
-    }
+    d.releasePool.clear();
 }
 
 void Window::customRender()
@@ -224,6 +202,7 @@ void Window::customRender()
         if (d.testStage == 2) {
             const QSize sz = d.tex->pixelSize();
             d.newTex = m_r->newTexture(QRhiTexture::RGBA8, sz);
+            d.releasePool << d.newTex;
             d.newTex->build();
 
             QImage empty(sz.width(), sz.height(), QImage::Format_RGBA8888);
@@ -269,6 +248,40 @@ void Window::customRender()
             desc.layers.append(layer);
             u->uploadTexture(d.newTex, desc);
         }
+
+        // Exercise texture object export/import.
+        if (d.testStage == 6) {
+            QRhiNativeHandles *h = d.tex->nativeHandles();
+            if (h) {
+#ifdef Q_OS_DARWIN
+                if (graphicsApi == Metal) {
+                    qDebug() << "Metal texture: " << static_cast<QRhiMetalTextureNativeHandles *>(h)->texture;
+                    // Now could cast to id<MTLTexture> and do something with
+                    // it, keeping in mind that copy operations are only done
+                    // in beginPass, while rendering into a texture may only
+                    // have proper results in current_frame + 2, or after a
+                    // finish(). The QRhiTexture still owns the native object.
+                }
+#endif
+                // omit for other backends, the idea is the same
+
+                d.importedTex = m_r->newTexture(QRhiTexture::RGBA8, d.tex->pixelSize());
+                d.releasePool << d.importedTex;
+                if (!d.importedTex->buildFrom(h))
+                    qWarning("Texture import failed");
+
+                // now d.tex and d.importedTex use the same MTLTexture
+                // underneath (owned by d.tex)
+
+                // switch to showing d.importedTex
+                auto bindings = d.srb->bindings();
+                bindings[1].stex.tex = d.importedTex;
+                d.srb->setBindings(bindings);
+                d.srb->build();
+            } else {
+                qWarning("Accessing native texture object is not supported");
+            }
+        }
     }
 
     QRhiCommandBuffer *cb = m_sc->currentFrameCommandBuffer();

src/rhi/qrhi.cpp

@@ -85,6 +85,17 @@ QRhiTexture::QRhiTexture(QRhiImplementation *rhi, Format format_, const QSize &p
 {
 }
 
+QRhiNativeHandles *QRhiTexture::nativeHandles()
+{
+    return nullptr;
+}
+
+bool QRhiTexture::buildFrom(QRhiNativeHandles *src)
+{
+    Q_UNUSED(src);
+    return false;
+}
+
 QRhiSampler::QRhiSampler(QRhiImplementation *rhi,
                          Filter magFilter_, Filter minFilter_, Filter mipmapMode_,
                          AddressMode u_, AddressMode v_, AddressMode w_)
@@ -629,6 +640,11 @@ bool QRhi::isFeatureSupported(QRhi::Feature feature) const
     return d->isFeatureSupported(feature);
 }
 
+QRhiNativeHandles *QRhi::nativeHandles()
+{
+    return d->nativeHandles();
+}
+
 QRhiGraphicsPipeline *QRhi::newGraphicsPipeline()
 {
     return d->createGraphicsPipeline();

src/rhi/qrhi.h

@@ -352,10 +352,15 @@ struct Q_RHI_EXPORT QRhiReadbackDescription
 
 Q_DECLARE_TYPEINFO(QRhiReadbackDescription, Q_MOVABLE_TYPE);
 
+struct Q_RHI_EXPORT QRhiNativeHandles
+{
+};
+
 class Q_RHI_EXPORT QRhiResource
 {
 public:
     virtual ~QRhiResource();
+
     virtual void release() = 0;
     void releaseAndDestroy();
 
@@ -471,6 +476,16 @@ public:
 
     virtual bool build() = 0;
 
+    // Returns a ptr to a QRhi<backend>TextureNativeHandles struct.
+    // Ownership of the native objects is not transfered.
+    virtual QRhiNativeHandles *nativeHandles();
+
+    // Calling this instead of build() allows importing an existing native
+    // texture object (must belong to the same device or a sharing context).
+    // Note that format, pixelSize, etc. must still be set correctly (typically
+    // via QRhi::newTexture()). Ownership of the native resource is not taken.
+    virtual bool buildFrom(QRhiNativeHandles *src);
+
 protected:
     QRhiTexture(QRhiImplementation *rhi, Format format_, const QSize &pixelSize_,
                 int sampleCount_, Flags flags_);
@@ -1220,6 +1235,10 @@ public:
     bool isTextureFormatSupported(QRhiTexture::Format format, QRhiTexture::Flags flags = QRhiTexture::Flags()) const;
     bool isFeatureSupported(QRhi::Feature feature) const;
 
+    // Returns a ptr to a QRhi<backend>NativeHandles struct.
+    // Ownership of the native objects is not transfered.
+    QRhiNativeHandles *nativeHandles();
+
 protected:
     QRhi();
 

src/rhi/qrhi_p.h

@@ -126,6 +126,7 @@ public:
     virtual QMatrix4x4 clipSpaceCorrMatrix() const = 0;
     virtual bool isTextureFormatSupported(QRhiTexture::Format format, QRhiTexture::Flags flags) const = 0;
     virtual bool isFeatureSupported(QRhi::Feature) const = 0;
+    virtual QRhiNativeHandles *nativeHandles() = 0;
 
     bool isCompressedFormat(QRhiTexture::Format format) const;
     void compressedFormatInfo(QRhiTexture::Format format, const QSize &size,

src/rhi/qrhid3d11.cpp

@@ -146,6 +146,9 @@ bool QRhiD3D11::create()
         featureLevel = dev->GetFeatureLevel();
     }
 
+    nativeHandlesStruct.dev = dev;
+    nativeHandlesStruct.context = context;
+
     return true;
 }
 
@@ -252,6 +255,11 @@ bool QRhiD3D11::isFeatureSupported(QRhi::Feature feature) const
     }
 }
 
+QRhiNativeHandles *QRhiD3D11::nativeHandles()
+{
+    return &nativeHandlesStruct;
+}
+
 QRhiRenderBuffer *QRhiD3D11::createRenderBuffer(QRhiRenderBuffer::Type type, const QSize &pixelSize,
                                                 int sampleCount, QRhiRenderBuffer::Flags flags)
 {

src/rhi/qrhid3d11.h

@@ -55,6 +55,12 @@ struct Q_RHI_EXPORT QRhiD3D11InitParams : public QRhiInitParams
     void *context = nullptr;
 };
 
+struct Q_RHI_EXPORT QRhiD3D11NativeHandles : public QRhiNativeHandles
+{
+    void *dev;
+    void *context;
+};
+
 QT_END_NAMESPACE
 
 #endif

src/rhi/qrhid3d11_p.h

@@ -485,6 +485,7 @@ public:
     QMatrix4x4 clipSpaceCorrMatrix() const override;
     bool isTextureFormatSupported(QRhiTexture::Format format, QRhiTexture::Flags flags) const override;
     bool isFeatureSupported(QRhi::Feature feature) const override;
+    QRhiNativeHandles *nativeHandles() override;
 
     void enqueueResourceUpdates(QRhiCommandBuffer *cb, QRhiResourceUpdateBatch *resourceUpdates);
     void updateShaderResourceBindings(QD3D11ShaderResourceBindings *srbD);
@@ -500,6 +501,7 @@ public:
     ID3D11DeviceContext1 *context = nullptr;
     D3D_FEATURE_LEVEL featureLevel;
     IDXGIFactory2 *dxgiFactory = nullptr;
+    QRhiD3D11NativeHandles nativeHandlesStruct;
 
     bool inFrame = false;
     int finishedFrameCount = 0;

src/rhi/qrhigles2.cpp

@@ -116,6 +116,8 @@ bool QRhiGles2::create()
     caps.msaaRenderBuffer = f->hasOpenGLExtension(QOpenGLExtensions::FramebufferMultisample)
             && f->hasOpenGLExtension(QOpenGLExtensions::FramebufferBlit);
 
+    nativeHandlesStruct.context = ctx;
+
     return true;
 }
 
@@ -264,6 +266,11 @@ bool QRhiGles2::isFeatureSupported(QRhi::Feature feature) const
     }
 }
 
+QRhiNativeHandles *QRhiGles2::nativeHandles()
+{
+    return &nativeHandlesStruct;
+}
+
 QRhiRenderBuffer *QRhiGles2::createRenderBuffer(QRhiRenderBuffer::Type type, const QSize &pixelSize,
                                                 int sampleCount, QRhiRenderBuffer::Flags flags)
 {

src/rhi/qrhigles2.h

@@ -62,6 +62,11 @@ struct Q_RHI_EXPORT QRhiGles2InitParams : public QRhiInitParams
     QOffscreenSurface *fallbackSurface = nullptr;
 };
 
+struct Q_RHI_EXPORT QRhiGles2NativeHandles : public QRhiNativeHandles
+{
+    QOpenGLContext *context;
+};
+
 QT_END_NAMESPACE
 
 #endif

src/rhi/qrhigles2_p.h

@@ -500,6 +500,7 @@ public:
     QMatrix4x4 clipSpaceCorrMatrix() const override;
     bool isTextureFormatSupported(QRhiTexture::Format format, QRhiTexture::Flags flags) const override;
     bool isFeatureSupported(QRhi::Feature feature) const override;
+    QRhiNativeHandles *nativeHandles() override;
 
     bool ensureContext(QSurface *surface = nullptr) const;
     void executeDeferredReleases();
@@ -523,6 +524,7 @@ public:
     bool inPass = false;
     QGles2SwapChain *currentSwapChain = nullptr;
     QVector<GLint> supportedCompressedFormats;
+    QRhiGles2NativeHandles nativeHandlesStruct;
 
     struct DeferredReleaseEntry {
         enum Type {

src/rhi/qrhimetal.h

@@ -50,7 +50,18 @@ struct Q_RHI_EXPORT QRhiMetalInitParams : public QRhiInitParams
     // API validation.
 
     bool importExistingDevice = false;
-    void *dev = nullptr;
+    void *dev = nullptr; // ownership not taken
+};
+
+struct Q_RHI_EXPORT QRhiMetalNativeHandles : public QRhiNativeHandles
+{
+    void *dev;
+    void *cmdQueue;
+};
+
+struct Q_RHI_EXPORT QRhiMetalTextureNativeHandles : public QRhiNativeHandles
+{
+    void *texture = nullptr; // id<MTLTexture>
 };
 
 QT_END_NAMESPACE

src/rhi/qrhimetal.mm

@@ -145,6 +145,7 @@ struct QMetalTextureData
     MTLPixelFormat format;
     id<MTLTexture> tex = nil;
     id<MTLBuffer> stagingBuf[QMTL_FRAMES_IN_FLIGHT];
+    bool owns = true;
 };
 
 struct QMetalSamplerData
@@ -237,6 +238,9 @@ bool QRhiMetal::create()
 
     d->cmdQueue = [d->dev newCommandQueue];
 
+    nativeHandlesStruct.dev = d->dev;
+    nativeHandlesStruct.cmdQueue = d->cmdQueue;
+
     return true;
 }
 
@@ -336,6 +340,11 @@ bool QRhiMetal::isFeatureSupported(QRhi::Feature feature) const
     }
 }
 
+QRhiNativeHandles *QRhiMetal::nativeHandles()
+{
+    return &nativeHandlesStruct;
+}
+
 QRhiRenderBuffer *QRhiMetal::createRenderBuffer(QRhiRenderBuffer::Type type, const QSize &pixelSize,
                                                 int sampleCount, QRhiRenderBuffer::Flags flags)
 {
@@ -1331,14 +1340,17 @@ void QMetalTexture::release()
 
     e.texture.texture = d->tex;
     d->tex = nil;
+    nativeHandlesStruct.texture = nullptr;
 
     for (int i = 0; i < QMTL_FRAMES_IN_FLIGHT; ++i) {
         e.texture.stagingBuffers[i] = d->stagingBuf[i];
         d->stagingBuf[i] = nil;
     }
 
-    QRHI_RES_RHI(QRhiMetal);
-    rhiD->d->releaseQueue.append(e);
+    if (d->owns) {
+        QRHI_RES_RHI(QRhiMetal);
+        rhiD->d->releaseQueue.append(e);
+    }
 }
 
 static inline MTLPixelFormat toMetalTextureFormat(QRhiTexture::Format format, QRhiTexture::Flags flags)
@@ -1502,6 +1514,40 @@ bool QMetalTexture::build()
     d->tex = [rhiD->d->dev newTextureWithDescriptor: desc];
     [desc release];
 
+    d->owns = true;
+    nativeHandlesStruct.texture = d->tex;
+
+    lastActiveFrameSlot = -1;
+    generation += 1;
+    return true;
+}
+
+QRhiNativeHandles *QMetalTexture::nativeHandles()
+{
+    return &nativeHandlesStruct;
+}
+
+bool QMetalTexture::buildFrom(QRhiNativeHandles *src)
+{
+    QRhiMetalTextureNativeHandles *h = static_cast<QRhiMetalTextureNativeHandles *>(src);
+    if (!h || !h->texture)
+        return false;
+
+    if (d->tex)
+        release();
+
+    QRHI_RES_RHI(QRhiMetal);
+    d->format = toMetalTextureFormat(m_format, m_flags);
+    const QSize size = m_pixelSize.isEmpty() ? QSize(16, 16) : m_pixelSize;
+    const bool hasMipMaps = m_flags.testFlag(MipMapped);
+    mipLevelCount = hasMipMaps ? qCeil(log2(qMax(size.width(), size.height()))) + 1 : 1;
+    samples = rhiD->effectiveSampleCount(m_sampleCount);
+
+    d->tex = (id<MTLTexture>) h->texture;
+
+    d->owns = false;
+    nativeHandlesStruct.texture = d->tex;
+
     lastActiveFrameSlot = -1;
     generation += 1;
     return true;

src/rhi/qrhimetal_p.h

@@ -93,8 +93,11 @@ struct QMetalTexture : public QRhiTexture
     ~QMetalTexture();
     void release() override;
     bool build() override;
+    QRhiNativeHandles *nativeHandles() override;
+    bool buildFrom(QRhiNativeHandles *src) override;
 
     QMetalTextureData *d;
+    QRhiMetalTextureNativeHandles nativeHandlesStruct;
     int mipLevelCount = 0;
     int samples = 1;
     uint generation = 0;
@@ -317,6 +320,7 @@ public:
     QMatrix4x4 clipSpaceCorrMatrix() const override;
     bool isTextureFormatSupported(QRhiTexture::Format format, QRhiTexture::Flags flags) const override;
     bool isFeatureSupported(QRhi::Feature feature) const override;
+    QRhiNativeHandles *nativeHandles() override;
 
     void executeDeferredReleases(bool forced = false);
     void finishActiveReadbacks(bool forced = false);
@@ -331,6 +335,7 @@ public:
     bool inPass = false;
     QMetalSwapChain *currentSwapChain = nullptr;
     QSet<QMetalSwapChain *> swapchains;
+    QRhiMetalNativeHandles nativeHandlesStruct;
 
     QRhiMetalData *d = nullptr;
 };

src/rhi/qrhivulkan.cpp

@@ -167,6 +167,7 @@ QRhiVulkan::QRhiVulkan(QRhiInitParams *params)
         gfxQueueFamilyIdx = vkparams->gfxQueueFamilyIdx;
         gfxQueue = vkparams->gfxQueue;
         cmdPool = vkparams->cmdPool;
+        allocator = vkparams->vmemAllocator;
     }
     maybeWindow = vkparams->window; // may be null
 }
@@ -281,24 +282,6 @@ bool QRhiVulkan::create()
     if (gfxQueueFamilyIdx != -1 && !gfxQueue)
         df->vkGetDeviceQueue(dev, gfxQueueFamilyIdx, 0, &gfxQueue);
 
-    VmaVulkanFunctions afuncs;
-    afuncs.vkGetPhysicalDeviceProperties = wrap_vkGetPhysicalDeviceProperties;
-    afuncs.vkGetPhysicalDeviceMemoryProperties = wrap_vkGetPhysicalDeviceMemoryProperties;
-    afuncs.vkAllocateMemory = wrap_vkAllocateMemory;
-    afuncs.vkFreeMemory = wrap_vkFreeMemory;
-    afuncs.vkMapMemory = wrap_vkMapMemory;
-    afuncs.vkUnmapMemory = wrap_vkUnmapMemory;
-    afuncs.vkFlushMappedMemoryRanges = wrap_vkFlushMappedMemoryRanges;
-    afuncs.vkInvalidateMappedMemoryRanges = wrap_vkInvalidateMappedMemoryRanges;
-    afuncs.vkBindBufferMemory = wrap_vkBindBufferMemory;
-    afuncs.vkBindImageMemory = wrap_vkBindImageMemory;
-    afuncs.vkGetBufferMemoryRequirements = wrap_vkGetBufferMemoryRequirements;
-    afuncs.vkGetImageMemoryRequirements = wrap_vkGetImageMemoryRequirements;
-    afuncs.vkCreateBuffer = wrap_vkCreateBuffer;
-    afuncs.vkDestroyBuffer = wrap_vkDestroyBuffer;
-    afuncs.vkCreateImage = wrap_vkCreateImage;
-    afuncs.vkDestroyImage = wrap_vkDestroyImage;
-
     f->vkGetPhysicalDeviceProperties(physDev, &physDevProperties);
     ubufAlign = physDevProperties.limits.minUniformBufferOffsetAlignment;
     texbufAlign = physDevProperties.limits.optimalBufferCopyOffsetAlignment;
@@ -308,26 +291,53 @@ bool QRhiVulkan::create()
            VK_VERSION_MINOR(physDevProperties.driverVersion),
            VK_VERSION_PATCH(physDevProperties.driverVersion));
 
-    VmaAllocatorCreateInfo allocatorInfo;
-    memset(&allocatorInfo, 0, sizeof(allocatorInfo));
-    allocatorInfo.physicalDevice = physDev;
-    allocatorInfo.device = dev;
-    allocatorInfo.pVulkanFunctions = &afuncs;
-    VmaAllocator vmaallocator;
-    VkResult err = vmaCreateAllocator(&allocatorInfo, &vmaallocator);
-    if (err != VK_SUCCESS) {
-        qWarning("Failed to create allocator: %d", err);
-        return false;
+    if (!allocator) {
+        VmaVulkanFunctions afuncs;
+        afuncs.vkGetPhysicalDeviceProperties = wrap_vkGetPhysicalDeviceProperties;
+        afuncs.vkGetPhysicalDeviceMemoryProperties = wrap_vkGetPhysicalDeviceMemoryProperties;
+        afuncs.vkAllocateMemory = wrap_vkAllocateMemory;
+        afuncs.vkFreeMemory = wrap_vkFreeMemory;
+        afuncs.vkMapMemory = wrap_vkMapMemory;
+        afuncs.vkUnmapMemory = wrap_vkUnmapMemory;
+        afuncs.vkFlushMappedMemoryRanges = wrap_vkFlushMappedMemoryRanges;
+        afuncs.vkInvalidateMappedMemoryRanges = wrap_vkInvalidateMappedMemoryRanges;
+        afuncs.vkBindBufferMemory = wrap_vkBindBufferMemory;
+        afuncs.vkBindImageMemory = wrap_vkBindImageMemory;
+        afuncs.vkGetBufferMemoryRequirements = wrap_vkGetBufferMemoryRequirements;
+        afuncs.vkGetImageMemoryRequirements = wrap_vkGetImageMemoryRequirements;
+        afuncs.vkCreateBuffer = wrap_vkCreateBuffer;
+        afuncs.vkDestroyBuffer = wrap_vkDestroyBuffer;
+        afuncs.vkCreateImage = wrap_vkCreateImage;
+        afuncs.vkDestroyImage = wrap_vkDestroyImage;
+
+        VmaAllocatorCreateInfo allocatorInfo;
+        memset(&allocatorInfo, 0, sizeof(allocatorInfo));
+        allocatorInfo.physicalDevice = physDev;
+        allocatorInfo.device = dev;
+        allocatorInfo.pVulkanFunctions = &afuncs;
+        VmaAllocator vmaallocator;
+        VkResult err = vmaCreateAllocator(&allocatorInfo, &vmaallocator);
+        if (err != VK_SUCCESS) {
+            qWarning("Failed to create allocator: %d", err);
+            return false;
+        }
+        allocator = vmaallocator;
     }
-    allocator = vmaallocator;
 
     VkDescriptorPool pool;
-    err = createDescriptorPool(&pool);
+    VkResult err = createDescriptorPool(&pool);
     if (err == VK_SUCCESS)
         descriptorPools.append(pool);
     else
         qWarning("Failed to create initial descriptor pool: %d", err);
 
+    nativeHandlesStruct.physDev = physDev;
+    nativeHandlesStruct.dev = dev;
+    nativeHandlesStruct.gfxQueueFamilyIdx = gfxQueueFamilyIdx;
+    nativeHandlesStruct.gfxQueue = gfxQueue;
+    nativeHandlesStruct.cmdPool = cmdPool;
+    nativeHandlesStruct.vmemAllocator = allocator;
+
     return true;
 }
 
@@ -361,9 +371,8 @@ void QRhiVulkan::destroy()
 
     descriptorPools.clear();
 
-    vmaDestroyAllocator(toVmaAllocator(allocator));
-
     if (!importedDevPoolQueue) {
+        vmaDestroyAllocator(toVmaAllocator(allocator));
         if (cmdPool) {
             df->vkDestroyCommandPool(dev, cmdPool, nullptr);
             cmdPool = VK_NULL_HANDLE;
@@ -2628,6 +2637,11 @@ bool QRhiVulkan::isFeatureSupported(QRhi::Feature feature) const
     }
 }
 
+QRhiNativeHandles *QRhiVulkan::nativeHandles()
+{
+    return &nativeHandlesStruct;
+}
+
 QRhiRenderBuffer *QRhiVulkan::createRenderBuffer(QRhiRenderBuffer::Type type, const QSize &pixelSize,
                                                  int sampleCount, QRhiRenderBuffer::Flags flags)
 {

src/rhi/qrhivulkan.h

@@ -54,6 +54,7 @@ struct Q_RHI_EXPORT QRhiVulkanInitParams : public QRhiInitParams
     int gfxQueueFamilyIdx = -1; // either this or gfxQueue is required [prefer this over gfxQueue]
     VkQueue gfxQueue = VK_NULL_HANDLE; // either this or gfxQueueFamilyIdx is required [use this only when importing a QVulkanWindow]
     VkCommandPool cmdPool = VK_NULL_HANDLE; // optional
+    void *vmemAllocator = nullptr; // optional
 
     // optional, only used during init to verify if presenting is supported
     // while choosing the graphics queue
@@ -61,6 +62,16 @@ struct Q_RHI_EXPORT QRhiVulkanInitParams : public QRhiInitParams
     QWindow *window = nullptr;
 };
 
+struct Q_RHI_EXPORT QRhiVulkanNativeHandles : public QRhiNativeHandles
+{
+    VkPhysicalDevice physDev;
+    VkDevice dev;
+    int gfxQueueFamilyIdx;
+    VkQueue gfxQueue;
+    VkCommandPool cmdPool;
+    void *vmemAllocator;
+};
+
 QT_END_NAMESPACE
 
 #endif