QVulkanWindow Class

class VulkanRenderer : public QVulkanWindowRenderer
{
public:
    VulkanRenderer(QVulkanWindow *w) : m_window(w) { }

    void initResources() override
    {
        m_devFuncs = m_window->vulkanInstance()->deviceFunctions(m_window->device());
        ...
    }
    void initSwapChainResources() override { ... }
    void releaseSwapChainResources() override { ... }
    void releaseResources() override { ... }

    void startNextFrame() override
    {
        VkCommandBuffer cmdBuf = m_window->currentCommandBuffer();
        ...
        m_devFuncs->vkCmdBeginRenderPass(...);
        ...
        m_window->frameReady();
    }

private:
    QVulkanWindow *m_window;
    QVulkanDeviceFunctions *m_devFuncs;
};

class VulkanWindow : public QVulkanWindow
{
public:
    QVulkanWindowRenderer *createRenderer() override {
        return new VulkanRenderer(this);
    }
};

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    QVulkanInstance inst;
    // enable the standard validation layers, when available
    inst.setLayers(QByteArrayList() << "VK_LAYER_LUNARG_standard_validation");
    if (!inst.create())
        qFatal("Failed to create Vulkan instance: %d", inst.errorCode());

    VulkanWindow w;
    w.setVulkanInstance(&inst);
    w.showMaximized();

    return app.exec();
}

Member Function Documentation

QVulkanWindow::QVulkanWindow(QWindow *parent = nullptr)

Constructs a new QVulkanWindow with the given parent.

The surface type is set to QSurface::VulkanSurface.

[virtual] QVulkanWindow::~QVulkanWindow()

Destructor.

int QVulkanWindow::availablePhysicalDevices()

Returns the list of properties for the supported physical devices in the system.

Note: This function can be called before making the window visible.

QMatrix4x4 QVulkanWindow::clipCorrectionMatrix()

Returns a QMatrix4x4 that can be used to correct for coordinate system differences between OpenGL and Vulkan.

By pre-multiplying the projection matrix with this matrix, applications can continue to assume OpenGL-style Y coordinates in clip space (i.e. Y pointing upwards), and can set minDepth and maxDepth to 0 and 1, respectively, without any further corrections to the vertex Z positions, while using the projection matrices retrieved from the QMatrix4x4 functions, such as QMatrix4x4::perspective(), as-is.

Note: With vertex data following the default OpenGL rules (that is, the front face being CCW), the correct winding order in the rasterization state after applying this matrix is clockwise (VK_FRONT_FACE_CLOCKWISE).

int QVulkanWindow::colorFormat() const

Returns the color buffer format used by the swapchain.

Note: Calling this function is only valid from the invocation of QVulkanWindowRenderer::initResources() up until QVulkanWindowRenderer::releaseResources().

See also setPreferredColorFormats().

int QVulkanWindow::concurrentFrameCount() const

Returns the number of frames that can be potentially active at the same time.

Note: The value is constant for the entire lifetime of the QVulkanWindow.

class Renderer {
    ...
    VkDescriptorBufferInfo m_uniformBufInfo[QVulkanWindow::MAX_CONCURRENT_FRAME_COUNT];
};

void Renderer::startNextFrame()
{
    const int count = m_window->concurrentFrameCount();
    for (int i = 0; i < count; ++i)
        m_uniformBufInfo[i] = ...
    ...
}

See also currentFrame().

[virtual] QVulkanWindowRenderer *QVulkanWindow::createRenderer()

Returns a new instance of QVulkanWindowRenderer.

This virtual function is called once during the lifetime of the window, at some point after making it visible for the first time.

The default implementation returns null and so no rendering will be performed apart from clearing the buffers.

The window takes ownership of the returned renderer object.

int QVulkanWindow::currentCommandBuffer() const

Returns The active command buffer for the current swap chain image. Implementations of QVulkanWindowRenderer::startNextFrame() are expected to add commands to this command buffer.

Note: This function must only be called from within startNextFrame() and, in case of asynchronous command generation, up until the call to frameReady().

int QVulkanWindow::currentFrame() const

Returns the current frame index in the range [0, concurrentFrameCount() - 1].

Renderer implementations will have to ensure that uniform data and other dynamic resources exist in multiple copies, in order to prevent frame N altering the data used by the still-active frames N - 1, N - 2, ... N - concurrentFrameCount() + 1.

To avoid relying on dynamic array sizes, applications can use MAX_CONCURRENT_FRAME_COUNT when declaring arrays. This is guaranteed to be always equal to or greater than the value returned from concurrentFrameCount(). Such arrays can then be indexed by the value returned from this function.

class Renderer {
    ...
    VkDescriptorBufferInfo m_uniformBufInfo[QVulkanWindow::MAX_CONCURRENT_FRAME_COUNT];
};

void Renderer::startNextFrame()
{
    VkDescriptorBufferInfo &uniformBufInfo(m_uniformBufInfo[m_window->currentFrame()]);
    ...
}

Note: This function must only be called from within startNextFrame() and, in case of asynchronous command generation, up until the call to frameReady().

See also concurrentFrameCount().

int QVulkanWindow::currentFramebuffer() const

Returns a VkFramebuffer for the current swapchain image using the default render pass.

The framebuffer has two attachments (color, depth-stencil) when multisampling is not in use, and three (color resolve, depth-stencil, multisample color) when sampleCountFlagBits() is greater than VK_SAMPLE_COUNT_1_BIT. Renderers must take this into account, for example when providing clear values.

Note: Applications are not required to use this framebuffer in case they provide their own render pass instead of using the one returned from defaultRenderPass().

Note: This function must only be called from within startNextFrame() and, in case of asynchronous command generation, up until the call to frameReady().

See also defaultRenderPass().

int QVulkanWindow::currentSwapChainImageIndex() const

Returns the current swap chain image index in the range [0, swapChainImageCount() - 1].

Note: This function must only be called from within startNextFrame() and, in case of asynchronous command generation, up until the call to frameReady().

int QVulkanWindow::defaultRenderPass() const

Returns a typical render pass with one sub-pass.

Note: Applications are not required to use this render pass. However, they are then responsible for ensuring the current swap chain and depth-stencil images get transitioned from VK_IMAGE_LAYOUT_UNDEFINED to VK_IMAGE_LAYOUT_PRESENT_SRC_KHR and VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL either via the application's custom render pass or by other means.

Note: Stencil read/write is not enabled in this render pass.

Note: Calling this function is only valid from the invocation of QVulkanWindowRenderer::initResources() up until QVulkanWindowRenderer::releaseResources().

See also currentFramebuffer().

int QVulkanWindow::depthStencilFormat() const

Returns the format used by the depth-stencil buffer(s).

Note: Calling this function is only valid from the invocation of QVulkanWindowRenderer::initResources() up until QVulkanWindowRenderer::releaseResources().

VkImage QVulkanWindow::depthStencilImage() const

Returns the depth-stencil image.

Note: Calling this function is only valid from the invocation of QVulkanWindowRenderer::initSwapChainResources() up until QVulkanWindowRenderer::releaseSwapChainResources().

VkImageView QVulkanWindow::depthStencilImageView() const

Returns the depth-stencil image view.

Note: Calling this function is only valid from the invocation of QVulkanWindowRenderer::initSwapChainResources() up until QVulkanWindowRenderer::releaseSwapChainResources().

int QVulkanWindow::device() const

Returns the active logical device.

Note: Calling this function is only valid from the invocation of QVulkanWindowRenderer::initResources() up until QVulkanWindowRenderer::releaseResources().

int QVulkanWindow::deviceLocalMemoryIndex() const

Returns a device local memory type index suitable for general use.

Note: Calling this function is only valid from the invocation of QVulkanWindowRenderer::initResources() up until QVulkanWindowRenderer::releaseResources().

QVulkanWindow::Flags QVulkanWindow::flags() const

Return the requested flags.

See also setFlags().

[signal] void QVulkanWindow::frameGrabbed(const QImage &image)

This signal is emitted when the image is ready.

void QVulkanWindow::frameReady()

This function must be called exactly once in response to each invocation of the QVulkanWindowRenderer::startNextFrame() implementation. At the time of this call, the main command buffer, exposed via currentCommandBuffer(), must have all necessary rendering commands added to it since this function will trigger submitting the commands and queuing the present command.

Note: This function must only be called from the gui/main thread, which is where QVulkanWindowRenderer's functions are invoked and where the QVulkanWindow instance lives.

See also QVulkanWindowRenderer::startNextFrame().

QImage QVulkanWindow::grab()

Builds and renders the next frame without presenting it, then performs a blocking readback of the image content.

Returns the image if the renderer's startNextFrame() implementation calls back frameReady() directly. Otherwise, returns an incomplete image, that has the correct size but not the content yet. The content will be delivered via the frameGrabbed() signal in the latter case.

Note: This function should not be called when a frame is in progress (that is, frameReady() has not yet been called back by the application).

Note: This function is potentially expensive due to the additional, blocking readback.

Note: This function currently requires that the swapchain supports usage as a transfer source (VK_IMAGE_USAGE_TRANSFER_SRC_BIT), and will fail otherwise.

int QVulkanWindow::graphicsCommandPool() const

Returns the active graphics command pool.

Note: Calling this function is only valid from the invocation of QVulkanWindowRenderer::initResources() up until QVulkanWindowRenderer::releaseResources().

int QVulkanWindow::graphicsQueue() const

Returns the active graphics queue.

Note: Calling this function is only valid from the invocation of QVulkanWindowRenderer::initResources() up until QVulkanWindowRenderer::releaseResources().

int QVulkanWindow::hostVisibleMemoryIndex() const

Returns a host visible memory type index suitable for general use.

The returned memory type will be both host visible and coherent. In addition, it will also be cached, if possible.

Note: Calling this function is only valid from the invocation of QVulkanWindowRenderer::initResources() up until QVulkanWindowRenderer::releaseResources().

bool QVulkanWindow::isValid() const

Returns true if this window has successfully initialized all Vulkan resources, including the swapchain.

Note: Initialization happens on the first expose event after the window is made visible.

VkImage QVulkanWindow::msaaColorImage(int idx) const

Returns the specified multisample color image, or VK_NULL_HANDLE if multisampling is not in use.

idx must be in the range [0, swapChainImageCount() - 1].

Note: Calling this function is only valid from the invocation of QVulkanWindowRenderer::initSwapChainResources() up until QVulkanWindowRenderer::releaseSwapChainResources().

VkImageView QVulkanWindow::msaaColorImageView(int idx) const

Returns the specified multisample color image view, or VK_NULL_HANDLE if multisampling is not in use.

idx must be in the range [0, swapChainImageCount() - 1].

Note: Calling this function is only valid from the invocation of QVulkanWindowRenderer::initSwapChainResources() up until QVulkanWindowRenderer::releaseSwapChainResources().

int QVulkanWindow::physicalDevice() const

Returns the active physical device.

Note: Calling this function is only valid from the invocation of QVulkanWindowRenderer::preInitResources() up until QVulkanWindowRenderer::releaseResources().

const int *QVulkanWindow::physicalDeviceProperties() const

Returns a pointer to the properties for the active physical device.

Note: Calling this function is only valid from the invocation of QVulkanWindowRenderer::preInitResources() up until QVulkanWindowRenderer::releaseResources().

int QVulkanWindow::sampleCountFlagBits() const

Returns the current sample count as a VkSampleCountFlagBits value.

When targeting the default render target, the rasterizationSamples field of VkPipelineMultisampleStateCreateInfo must be set to this value.

See also setSampleCount() and supportedSampleCounts().

void QVulkanWindow::setDeviceExtensions(const QByteArrayList &extensions)

Sets the list of device extensions to be enabled.

Unsupported extensions are ignored.

The swapchain extension will always be added automatically, no need to include it in this list.

Note: This function must be called before the window is made visible or at latest in QVulkanWindowRenderer::preInitResources(), and has no effect if called afterwards.

void QVulkanWindow::setFlags(QVulkanWindow::Flags flags)

Configures the behavior based on the provided flags.

Note: This function must be called before the window is made visible or at latest in QVulkanWindowRenderer::preInitResources(), and has no effect if called afterwards.

See also flags().

void QVulkanWindow::setPhysicalDeviceIndex(int idx)

Requests the usage of the physical device with index idx. The index corresponds to the list returned from availablePhysicalDevices().

By default the first physical device is used.

Note: This function must be called before the window is made visible or at latest in QVulkanWindowRenderer::preInitResources(), and has no effect if called afterwards.

void QVulkanWindow::setPreferredColorFormats(const int &formats)

Sets the preferred formats of the swapchain.

By default no application-preferred format is set. In this case the surface's preferred format will be used or, in absence of that, VK_FORMAT_B8G8R8A8_UNORM.

The list in formats is ordered. If the first format is not supported, the second will be considered, and so on. When no formats in the list are supported, the behavior is the same as in the default case.

To query the actual format after initialization, call colorFormat().

Note: This function must be called before the window is made visible or at latest in QVulkanWindowRenderer::preInitResources(), and has no effect if called afterwards.

Note: Reimplementing QVulkanWindowRenderer::preInitResources() allows dynamically examining the list of supported formats, should that be desired. There the surface is retrievable via QVulkanInstace::surfaceForWindow(), while this function can still safely be called to affect the later stages of initialization.

See also colorFormat().

void QVulkanWindow::setSampleCount(int sampleCount)

Requests multisample antialiasing with the given sampleCount. The valid values are 1, 2, 4, 8, ... up until the maximum value supported by the physical device.

When the sample count is greater than 1, QVulkanWindow will create a multisample color buffer instead of simply targeting the swapchain's images. The rendering in the multisample buffer will get resolved into the non-multisample buffers at the end of each frame.

To examine the list of supported sample counts, call supportedSampleCounts().

When setting up the rendering pipeline, call sampleCountFlagBits() to query the active sample count as a VkSampleCountFlagBits value.

Note: This function must be called before the window is made visible or at latest in QVulkanWindowRenderer::preInitResources(), and has no effect if called afterwards.

See also supportedSampleCounts() and sampleCountFlagBits().

QVulkanInfoVector<QVulkanExtension> QVulkanWindow::supportedDeviceExtensions()

Returns the list of the extensions that are supported by logical devices created from the physical device selected by setPhysicalDeviceIndex().

Note: This function can be called before making the window visible.

QVector<int> QVulkanWindow::supportedSampleCounts()

Returns the set of supported sample counts when using the physical device selected by setPhysicalDeviceIndex(), as a sorted vector.

By default QVulkanWindow uses a sample count of 1. By calling setSampleCount() with a different value (2, 4, 8, ...) from the set returned by this function, multisample anti-aliasing can be requested.

Note: This function can be called before making the window visible.

See also setSampleCount().

bool QVulkanWindow::supportsGrab() const

Returns true if the swapchain supports usage as transfer source, meaning grab() is functional.

Note: Calling this function is only valid from the invocation of QVulkanWindowRenderer::initSwapChainResources() up until QVulkanWindowRenderer::releaseSwapChainResources().

VkImage QVulkanWindow::swapChainImage(int idx) const

Returns the specified swap chain image.

idx must be in the range [0, swapChainImageCount() - 1].

Note: Calling this function is only valid from the invocation of QVulkanWindowRenderer::initSwapChainResources() up until QVulkanWindowRenderer::releaseSwapChainResources().

int QVulkanWindow::swapChainImageCount() const

Returns the number of images in the swap chain.

Note: Accessing this is necessary when providing a custom render pass and framebuffer. The framebuffer is specific to the current swapchain image and hence the application must provide multiple framebuffers.

Note: Calling this function is only valid from the invocation of QVulkanWindowRenderer::initSwapChainResources() up until QVulkanWindowRenderer::releaseSwapChainResources().

QSize QVulkanWindow::swapChainImageSize() const

Returns the image size of the swapchain.

This usually matches the size of the window, but may also differ in case vkGetPhysicalDeviceSurfaceCapabilitiesKHR reports a fixed size.

Note: Calling this function is only valid from the invocation of QVulkanWindowRenderer::initSwapChainResources() up until QVulkanWindowRenderer::releaseSwapChainResources().

VkImageView QVulkanWindow::swapChainImageView(int idx) const

Returns the specified swap chain image view.

idx must be in the range [0, swapChainImageCount() - 1].

Note: Calling this function is only valid from the invocation of QVulkanWindowRenderer::initSwapChainResources() up until QVulkanWindowRenderer::releaseSwapChainResources().