[[wsi]] = Window System Integration (WSI) This chapter discusses the window system integration (WSI) between the Vulkan API and the various forms of displaying the results of rendering to a user. Since the Vulkan API can: be used without displaying results, WSI is provided through the use of optional Vulkan extensions. This chapter provides an overview of WSI. See the appendix for additional details of each WSI extension, including which extensions must: be enabled in order to use each of the functions described in this chapter. == WSI Platform A platform is an abstraction for a window system, OS, etc. Some examples include MS Windows, Android, and Wayland. The Vulkan API may: be integrated in a unique manner for each platform. The Vulkan API does not define any type of platform object. Platform-specific WSI extensions are defined, which contain platform-specific functions for using WSI. Use of these extensions is guarded by preprocessor symbols as defined in the <> appendix. In order for an application to be compiled to use WSI with a given platform, it must: #define the appropriate preprocessor symbol prior to including the "vulkan.h" header file. Each platform-specific extension is an instance extension. The application must: enable instance extensions with fname:vkCreateInstance before using them. == WSI Surface A sname:VkSurfaceKHR object abstracts a native platform surface or window object for use with Vulkan. The VK_KHR_surface extension declares the sname:VkSurfaceKHR object, and provides a function for destroying sname:VkSurfaceKHR objects. Separate platform-specific extensions each provide a function for creating a sname:VkSurfaceKHR object for the respective platform. From the application's perspective this is an opaque handle, just like the handles of other Vulkan objects. ifdef::implementation-guide[] [NOTE] .Note ==== On certain platforms, the Vulkan loader and ICDs may: have conventions that treat the handle as a pointer to a struct that contains the platform-specific information about the surface. This will be described in the documentation for the loader-ICD interface, and in the "vk_icd.h" header file of the LoaderAndTools source-code repository. This does not affect the loader-layer interface; layers may: wrap sname:VkSurfaceKHR objects. ==== ifdef::editing-notes[] [NOTE] .editing-note ==== TODO: Consider replacing the above note editing note with a pointer to the loader spec when it exists. However, the information is not relevant to users of the API nor does it affect conformance of a Vulkan implementation to this spec. ==== endif::editing-notes[] endif::implementation-guide[] ifdef::VK_KHR_android_surface[] include::../VK_KHR_android_surface/platformCreateSurface_android.txt[] endif::VK_KHR_android_surface[] ifdef::VK_KHR_mir_surface[] include::../VK_KHR_mir_surface/platformCreateSurface_mir.txt[] endif::VK_KHR_mir_surface[] ifdef::VK_KHR_wayland_surface[] include::../VK_KHR_wayland_surface/platformCreateSurface_wayland.txt[] endif::VK_KHR_wayland_surface[] ifdef::VK_KHR_win32_surface[] include::../VK_KHR_win32_surface/platformCreateSurface_win32.txt[] endif::VK_KHR_win32_surface[] ifdef::VK_KHR_xcb_surface[] include::../VK_KHR_xcb_surface/platformCreateSurface_xcb.txt[] endif::VK_KHR_xcb_surface[] ifdef::VK_KHR_xlib_surface[] include::../VK_KHR_xlib_surface/platformCreateSurface_xlib.txt[] endif::VK_KHR_xlib_surface[] === Platform-Independent Information Once created, sname:VkSurfaceKHR objects can: be used in this and other extensions, in particular the VK_KHR_swapchain extension. Several WSI functions return ename:VK_ERROR_SURFACE_LOST_KHR if the surface becomes no longer available. After such an error, the surface (and any child swapchain, if one exists) should: be destroyed, as there is no way to restore them to a not-lost state. Applications may: attempt to create a new sname:VkSurfaceKHR using the same native platform window object, but whether such re-creation will succeed is platform-dependent and may: depend on the reason the surface became unavailable. A lost surface does not otherwise cause devices to be <>. // refBegin vkDestroySurfaceKHR - Destroy a VkSurfaceKHR object To destroy a sname:VkSurfaceKHR object, call: include::../../api/protos/vkDestroySurfaceKHR.txt[] * pname:instance is the instance used to create the surface. * pname:surface is the surface to destroy. * pname:pAllocator is the allocator used for host memory allocated for the surface object when there is no more specific allocator available (see <>). Destroying a sname:VkSurfaceKHR merely severs the connection between Vulkan and the native surface, and doesn't imply destroying the native surface, closing a window, or similar behavior. include::../../validity/protos/vkDestroySurfaceKHR.txt[] ifdef::VK_KHR_display[] include::../VK_KHR_display/display.txt[] endif::VK_KHR_display[] == Querying for WSI Support Not all physical devices will include WSI support. Within a physical device, not all queue families will support presentation. WSI support and compatibility can: be determined in a platform-neutral manner (which determines support for presentation to a particular surface object) and additionally may: be determined in platform-specific manners (which determine support for presentation on the specified physical device but don't guarantee support for presentation to a particular surface object). // refBegin vkGetPhysicalDeviceSurfaceSupportKHR - Query if presentation is supported To determine whether a queue family of a physical device supports presentation to a given surface, call: include::../../api/protos/vkGetPhysicalDeviceSurfaceSupportKHR.txt[] * pname:physicalDevice is the physical device. * pname:queueFamilyIndex is the queue family. * pname:surface is the surface. * pname:pSupported is a pointer to a basetype:VkBool32, which is set to ename:VK_TRUE to indicate support, and ename:VK_FALSE otherwise. include::../../validity/protos/vkGetPhysicalDeviceSurfaceSupportKHR.txt[] ifdef::VK_KHR_android_surface[] include::../VK_KHR_android_surface/platformQuerySupport_android.txt[] endif::VK_KHR_android_surface[] ifdef::VK_KHR_mir_surface[] include::../VK_KHR_mir_surface/platformQuerySupport_mir.txt[] endif::VK_KHR_mir_surface[] ifdef::VK_KHR_wayland_surface[] include::../VK_KHR_wayland_surface/platformQuerySupport_wayland.txt[] endif::VK_KHR_wayland_surface[] ifdef::VK_KHR_win32_surface[] include::../VK_KHR_win32_surface/platformQuerySupport_win32.txt[] endif::VK_KHR_win32_surface[] ifdef::VK_KHR_xcb_surface[] include::../VK_KHR_xcb_surface/platformQuerySupport_xcb.txt[] endif::VK_KHR_xcb_surface[] ifdef::VK_KHR_xlib_surface[] include::../VK_KHR_xlib_surface/platformQuerySupport_xlib.txt[] endif::VK_KHR_xlib_surface[] == Surface Queries // refBegin vkGetPhysicalDeviceSurfaceCapabilitiesKHR - Query surface capabilities To query the basic capabilities of a surface, needed in order to create a swapchain, call: include::../../api/protos/vkGetPhysicalDeviceSurfaceCapabilitiesKHR.txt[] * pname:physicalDevice is the physical device that will be associated with the swapchain to be created, as described for flink:vkCreateSwapchainKHR. * pname:surface is the surface that will be associated with the swapchain. * pname:pSurfaceCapabilities is a pointer to an instance of the slink:VkSurfaceCapabilitiesKHR structure in which the capabilities are returned. include::../../validity/protos/vkGetPhysicalDeviceSurfaceCapabilitiesKHR.txt[] // refBegin VkSurfaceCapabilitiesKHR - Structure describing capabilities of a surface The sname:VkSurfaceCapabilitiesKHR structure is defined as: include::../../api/structs/VkSurfaceCapabilitiesKHR.txt[] * pname:minImageCount is the minimum number of images the specified device supports for a swapchain created for the surface. * pname:maxImageCount is the maximum number of images the specified device supports for a swapchain created for the surface. A value of `0` means that there is no limit on the number of images, though there may: be limits related to the total amount of memory used by swapchain images. * pname:currentExtent is the current width and height of the surface, or the special value latexmath:[$(0xFFFFFFFF, 0xFFFFFFFF)$] indicating that the surface size will be determined by the extent of a swapchain targeting the surface. * pname:minImageExtent contains the smallest valid swapchain extent for the surface on the specified device. * pname:maxImageExtent contains the largest valid swapchain extent for the surface on the specified device. * pname:maxImageArrayLayers is the maximum number of layers swapchain images can: have for a swapchain created for this device and surface. * pname:supportedTransforms is a bitmask of elink:VkSurfaceTransformFlagBitsKHR, describing the presentation transforms supported for the surface on the specified device. * pname:currentTransform is a bitmask of elink:VkSurfaceTransformFlagBitsKHR, describing the surface's current transform relative to the presentation engine's natural orientation. * pname:supportedCompositeAlpha is a bitmask of elink:VkCompositeAlphaFlagBitsKHR, representing the alpha compositing modes supported by the presentation engine for the surface on the specified device. Opaque composition can: be achieved in any alpha compositing mode by either using a swapchain image format that has no alpha component, or by ensuring that all pixels in the swapchain images have an alpha value of 1.0. * pname:supportedUsageFlags is a bitmask of elink:VkImageUsageFlagBits representing the ways the application can: use the presentable images of a swapchain created for the surface on the specified device. ename:VK_IMAGE_USAGE_COLOR_ATTACHMENT_BIT must: be included in the set but implementations may: support additional usages. include::../../validity/structs/VkSurfaceCapabilitiesKHR.txt[] // refBegin VkSurfaceTransformFlagBitsKHR - presentation transforms supported on a device The pname:supportedTransforms and pname:currentTransform members are of type ename:VkSurfaceTransformFlagBitsKHR, which contains the following values: include::../../api/enums/VkSurfaceTransformFlagBitsKHR.txt[] These values are described as follows: * ename:VK_SURFACE_TRANSFORM_IDENTITY_BIT_KHR: The image content is presented without being transformed. * ename:VK_SURFACE_TRANSFORM_ROTATE_90_BIT_KHR: The image content is rotated 90 degrees clockwise. * ename:VK_SURFACE_TRANSFORM_ROTATE_180_BIT_KHR: The image content is rotated 180 degrees clockwise. * ename:VK_SURFACE_TRANSFORM_ROTATE_270_BIT_KHR: The image content is rotated 270 degrees clockwise. * ename:VK_SURFACE_TRANSFORM_HORIZONTAL_MIRROR_BIT_KHR: The image content is mirrored horizontally. * ename:VK_SURFACE_TRANSFORM_HORIZONTAL_MIRROR_ROTATE_90_BIT_KHR: The image content is mirrored horizontally, then rotated 90 degrees clockwise. * ename:VK_SURFACE_TRANSFORM_HORIZONTAL_MIRROR_ROTATE_180_BIT_KHR: The image content is mirrored horizontally, then rotated 180 degrees clockwise. * ename:VK_SURFACE_TRANSFORM_HORIZONTAL_MIRROR_ROTATE_270_BIT_KHR: The image content is mirrored horizontally, then rotated 270 degrees clockwise. * ename:VK_SURFACE_TRANSFORM_INHERIT_BIT_KHR: The presentation transform is not specified, and is instead determined by platform-specific considerations and mechanisms outside Vulkan. // refEnd VkSurfaceTransformFlagBitsKHR // refBegin VkCompositeAlphaFlagBitsKHR - alpha compositing modes supported on a device The pname:supportedCompositeAlpha member is of type ename:VkCompositeAlphaFlagBitsKHR, which contains the following values: include::../../api/enums/VkCompositeAlphaFlagBitsKHR.txt[] These values are described as follows: * ename:VK_COMPOSITE_ALPHA_OPAQUE_BIT_KHR: The alpha channel, if it exists, of the images is ignored in the compositing process. Instead, the image is treated as if it has a constant alpha of 1.0. * ename:VK_COMPOSITE_ALPHA_PRE_MULTIPLIED_BIT_KHR: The alpha channel, if it exists, of the images is respected in the compositing process. The non-alpha channels of the image are expected to already be multiplied by the alpha channel by the application. * ename:VK_COMPOSITE_ALPHA_POST_MULTIPLIED_BIT_KHR: The alpha channel, if it exists, of the images is respected in the compositing process. The non-alpha channels of the image are not expected to already be multiplied by the alpha channel by the application; instead, the compositor will multiply the non-alpha channels of the image by the alpha channel during compositing. * ename:VK_COMPOSITE_ALPHA_INHERIT_BIT_KHR: The way in which the presentation engine treats the alpha channel in the images is unknown to the Vulkan API. Instead, the application is responsible for setting the composite alpha blending mode using native window system commands. If the application does not set the blending mode using native window system commands, then a platform-specific default will be used. // refEnd VkCompositeAlphaFlagBitsKHR // refBegin vkGetPhysicalDeviceSurfaceFormatsKHR - Query color formats supported by surface To query the supported swapchain format-color space pairs for a surface, call: include::../../api/protos/vkGetPhysicalDeviceSurfaceFormatsKHR.txt[] * pname:physicalDevice is the physical device that will be associated with the swapchain to be created, as described for flink:vkCreateSwapchainKHR. * pname:surface is the surface that will be associated with the swapchain. * pname:pSurfaceFormatCount is a pointer to an integer related to the number of format pairs available or queried, as described below. * pname:pSurfaceFormats is either `NULL` or a pointer to an array of sname:VkSurfaceFormatKHR structures. If pname:pSurfaceFormats is `NULL`, then the number of format pairs supported for the given pname:surface is returned in pname:pSurfaceFormatCount. Otherwise, pname:pSurfaceFormatCount must: point to a variable set by the user to the number of elements in the pname:pSurfaceFormats array, and on return the variable is overwritten with the number of structures actually written to pname:pSurfaceFormats. If the value of pname:pSurfaceFormatCount is less than the number of format pairs supported, at most pname:pSurfaceFormatCount structures will be written. If pname:pSurfaceFormatCount is smaller than the number of format pairs supported for the given pname:surface, ename:VK_INCOMPLETE will be returned instead of ename:VK_SUCCESS to indicate that not all the available values were returned. include::../../validity/protos/vkGetPhysicalDeviceSurfaceFormatsKHR.txt[] // refBegin VkSurfaceFormatKHR - Structure describing a supported swapchain format-color space pair The sname:VkSurfaceFormatKHR structure is defined as: include::../../api/structs/VkSurfaceFormatKHR.txt[] * pname:format is a ename:VkFormat that is compatible with the specified surface. * pname:colorSpace is a presentation ename:VkColorSpaceKHR that is compatible with the surface. include::../../validity/structs/VkSurfaceFormatKHR.txt[] While the pname:format of a presentable image refers to the encoding of each pixel, the pname:colorSpace determines how the presentation engine interprets the pixel values. A color space in this document refers to a specific combination of color model (i.e. RGB, YUV, HSL etc.), the actual color space (defined by the chromaticities of its primaries and a white point in CIE Lab), and a transfer function that is applied before storing or transmitting color data in the given color space. // refBegin VkColorSpaceKHR - supported color space of the presentation engine The ename:VkColorSpaceKHR is defined as follows: include::../../api/enums/VkColorSpaceKHR.txt[] * ename:VK_COLOR_SPACE_SRGB_NONLINEAR_KHR: The presentation engine supports the sRGB color space. [NOTE] .Note ==== If pname:pSurfaceFormats includes just one entry, whose value for pname:format is ename:VK_FORMAT_UNDEFINED, pname:surface has no preferred format. In this case, the application can use any valid ename:VkFormat value. ==== [NOTE] .Note ==== In the initial release of the VK_KHR_surface and VK_KHR_swapchain extensions, the token ename:VK_COLORSPACE_SRGB_NONLINEAR_KHR was used. Starting in the May 13, 2016 updates to the extension branches, matching release 1.0.13 of the core API specification, ename:VK_COLOR_SPACE_SRGB_NONLINEAR_KHR is used instead for consistency with Vulkan naming rules. The older enum is still available for backwards compatibility. ==== // refEnd VkColorSpaceKHR // refBegin vkGetPhysicalDeviceSurfacePresentModesKHR - Query supported presentation modes To query the supported presentation modes for a surface, call: include::../../api/protos/vkGetPhysicalDeviceSurfacePresentModesKHR.txt[] * pname:physicalDevice is the physical device that will be associated with the swapchain to be created, as described for flink:vkCreateSwapchainKHR. * pname:surface is the surface that will be associated with the swapchain. * pname:pPresentModeCount is a pointer to an integer related to the number of presentation modes available or queried, as described below. * pname:pPresentModes is either `NULL` or a pointer to an array of elink:VkPresentModeKHR structures. If pname:pPresentModes is `NULL`, then the number of presentation modes supported for the given pname:surface is returned in pname:pPresentModeCount. Otherwise, pname:pPresentModeCount must: point to a variable set by the user to the number of elements in the pname:pPresentModes array, and on return the variable is overwritten with the number of values actually written to pname:pPresentModes. If the value of pname:pPresentModeCount is less than the number of presentation modes supported, at most pname:pPresentModeCount values will be written. If pname:pPresentModeCount is smaller than the number of presentation modes supported for the given pname:surface, ename:VK_INCOMPLETE will be returned instead of ename:VK_SUCCESS to indicate that not all the available values were returned. include::../../validity/protos/vkGetPhysicalDeviceSurfacePresentModesKHR.txt[] // refBegin VkPresentModeKHR - presentation mode supported for a surface The definition of ename:VkPresentModeKHR is: include::../../api/enums/VkPresentModeKHR.txt[] * ename:VK_PRESENT_MODE_IMMEDIATE_KHR: The presentation engine does not wait for a vertical blanking period to update the current image, meaning this mode may: result in visible tearing. No internal queuing of presentation requests is needed, as the requests are applied immediately. * ename:VK_PRESENT_MODE_MAILBOX_KHR: The presentation engine waits for the next vertical blanking period to update the current image. Tearing cannot: be observed. An internal single-entry queue is used to hold pending presentation requests. If the queue is full when a new presentation request is received, the new request replaces the existing entry, and any images associated with the prior entry become available for re-use by the application. One request is removed from the queue and processed during each vertical blanking period in which the queue is non-empty. * ename:VK_PRESENT_MODE_FIFO_KHR: The presentation engine waits for the next vertical blanking period to update the current image. Tearing cannot: be observed. An internal queue is used to hold pending presentation requests. New requests are appended to the end of the queue, and one request is removed from the beginning of the queue and processed during each vertical blanking period in which the queue is non-empty. This is the only value of pname:presentMode that is required: to be supported. * ename:VK_PRESENT_MODE_FIFO_RELAXED_KHR: The presentation engine generally waits for the next vertical blanking period to update the current image. If a vertical blanking period has already passed since the last update of the current image then the presentation engine does not wait for another vertical blanking period for the update, meaning this mode may: result in visible tearing in this case. This mode is useful for reducing visual stutter with an application that will mostly present a new image before the next vertical blanking period, but may occasionally be late, and present a new image just after the next vertical blanking period. An internal queue is used to hold pending presentation requests. New requests are appended to the end of the queue, and one request is removed from the beginning of the queue and processed during or after each vertical blanking period in which the queue is non-empty. [NOTE] .Note ==== For reference, the mode indicated by ename:VK_PRESENT_MODE_FIFO_KHR is equivalent to the behavior of {wgl|glX|egl}SwapBuffers with a swap interval of 1, while the mode indicated by ename:VK_PRESENT_MODE_FIFO_RELAXED_KHR is equivalent to the behavior of {wgl|glX}SwapBuffers with a swap interval of -1 (from the {WGL|GLX}_EXT_swap_control_tear extensions). ==== // refEnd VkPresentModeKHR ifdef::VK_KHR_swapchain[] include::../VK_KHR_swapchain/wsi.txt[] endif::VK_KHR_swapchain[]