- Qt 5.15
- Qt GUI
- C++ Classes
- QVulkanDeviceFunctions
- Qt 5.15.18 Reference Documentation

# QVulkanDeviceFunctions Class

The QVulkanDeviceFunctions class provides cross-platform access to the device level core Vulkan 1.0 API. More...

Header: | #include <QVulkanDeviceFunctions>
qmake: | QT += gui
Since: | Qt 5.10

This class was introduced in Qt 5.10.

## Detailed Description

Qt and Qt applications do not link to any Vulkan libraries by default. Instead, all functions are resolved dynamically at run time. Each QVulkanInstance provides a QVulkanFunctions object retrievable via QVulkanInstance::functions(). This does not contain device level functions in order to avoid the potential overhead of an internal dispatching. Instead, functions that rely on a device, or a dispatchable child object of a device, are exposed via QVulkanDeviceFunctions and QVulkanInstance::deviceFunctions(). QVulkanFunctions and QVulkanDeviceFunctions together provides access to the full core Vulkan API, excluding any extensions.

Note: QVulkanDeviceFunctions instances cannot be constructed directly.

The typical usage is the following:

         void Window::render()
         {
             QVulkanInstance *inst = vulkanInstance();
             QVulkanDeviceFunctions *df = inst->deviceFunctions(device);
             VkResult err = df->vkAllocateCommandBuffers(device, &cmdBufInfo, &cmdBuf);
             ...
         }

The QVulkanDeviceFunctions object specific to the provided VkDevice is created when QVulkanInstance::deviceFunctions() is first called with the device in question. The object is then cached internally.

To access additional functions, applications can use QVulkanInstance::getInstanceProcAddr() and vkGetDeviceProcAddr(). Applications can also decide to link to a Vulkan library directly, as many implementations export function symbols for the core commands. See the man page for vkGetInstanceProcAddr for more information.

See also QVulkanInstance, QVulkanFunctions, QWindow::setVulkanInstance(), and QWindow::setSurfaceType().