// Copyright (c) 2014-2017 The Khronos Group Inc.
// Copyright notice at https://www.khronos.org/registry/speccopyright.html

[[display,display]]

== Presenting Directly to Display Devices

In some environments applications can: also present Vulkan rendering
directly to display devices without using an intermediate windowing system.
This can: be useful for embedded applications, or implementing the
rendering/presentation backend of a windowing system using Vulkan.
The +VK_KHR_display+ extension provides the functionality necessary to
enumerate display devices and create sname:VkSurfaceKHR objects that target
displays.


=== Display Enumeration

// refBegin VkDisplayKHR - Opaque handle to a display object

Displays are represented by sname:VkDisplayKHR handles:

include::../../api/handles/VkDisplayKHR.txt[]

// refEnd VkDisplayKHR

// refBegin vkGetPhysicalDeviceDisplayPropertiesKHR - Query information about the available displays

Various functions are provided for enumerating the available display devices
present on a Vulkan physical device.
To query information about the available displays, call:

include::../../api/protos/vkGetPhysicalDeviceDisplayPropertiesKHR.txt[]

  * pname:physicalDevice is a physical device.
  * pname:pPropertyCount is a pointer to an integer related to the number of
    display devices available or queried, as described below.
  * pname:pProperties is either `NULL` or a pointer to an array of
    sname:VkDisplayPropertiesKHR structures.

If pname:pProperties is `NULL`, then the number of display devices available
for pname:physicalDevice is returned in pname:pPropertyCount.
Otherwise, pname:pPropertyCount must: point to a variable set by the user to
the number of elements in the pname:pProperties array, and on return the
variable is overwritten with the number of structures actually written to
pname:pProperties.
If the value of pname:pPropertyCount is less than the number of display
devices for pname:physicalDevice, at most pname:pPropertyCount structures
will be written.
If pname:pPropertyCount is smaller than the number of display devices
available for pname:physicalDevice, ename:VK_INCOMPLETE will be returned
instead of ename:VK_SUCCESS to indicate that not all the available values
were returned.

include::../../validity/protos/vkGetPhysicalDeviceDisplayPropertiesKHR.txt[]

// refBegin VkDisplayPropertiesKHR - Structure describing an available display device

The sname:VkDisplayPropertiesKHR structure is defined as:

include::../../api/structs/VkDisplayPropertiesKHR.txt[]

  * pname:display is a handle that is used to refer to the display described
    here.
    This handle will be valid for the lifetime of the Vulkan instance.
  * pname:displayName is a pointer to a NULL-terminated string containing
    the name of the display.
    Generally, this will be the name provided by the display's EDID.
    It can: be `NULL` if no suitable name is available.
    If not `NULL`, the memory it points to must: remain accessible as long
    as pname:display is valid.
  * pname:physicalDimensions describes the physical width and height of the
    visible portion of the display, in millimeters.
  * pname:physicalResolution describes the physical, native, or preferred
    resolution of the display.

[NOTE]
.Note
====
For devices which have no natural value to return here, implementations
should: return the maximum resolution supported.
====

  * pname:supportedTransforms tells which transforms are supported by this
    display.
    This will contain one or more of the bits from
    sname:VkSurfaceTransformFlagsKHR.
  * pname:planeReorderPossible tells whether the planes on this display can:
    have their z order changed.
    If this is ename:VK_TRUE, the application can: re-arrange the planes on
    this display in any order relative to each other.
  * pname:persistentContent tells whether the display supports
    self-refresh/internal buffering.
    If this is true, the application can: submit persistent present
    operations on swapchains created against this display.

[NOTE]
.Note
====
Persistent presents may: have higher latency, and may: use less power when
the screen content is updated infrequently, or when only a portion of the
screen needs to be updated in most frames.
====

include::../../validity/structs/VkDisplayPropertiesKHR.txt[]

ifdef::VK_EXT_direct_mode_display[]
include::../VK_EXT_direct_mode_display/acquire_release_displays.txt[]
endif::VK_EXT_direct_mode_display[]

==== Display Planes

// refBegin vkGetPhysicalDeviceDisplayPlanePropertiesKHR - Query the plane properties

Images are presented to individual planes on a display.
Devices must: support at least one plane on each display.
Planes can: be stacked and blended to composite multiple images on one
display.
Devices may: support only a fixed stacking order and fixed mapping between
planes and displays, or they may: allow arbitrary application specified
stacking orders and mappings between planes and displays.
To query the properties of device display planes, call:

include::../../api/protos/vkGetPhysicalDeviceDisplayPlanePropertiesKHR.txt[]

  * pname:physicalDevice is a physical device.
  * pname:pPropertyCount is a pointer to an integer related to the number of
    display planes available or queried, as described below.
  * pname:pProperties is either `NULL` or a pointer to an array of
    sname:VkDisplayPlanePropertiesKHR structures.

If pname:pProperties is `NULL`, then the number of display planes available
for pname:physicalDevice is returned in pname:pPropertyCount.
Otherwise, pname:pPropertyCount must: point to a variable set by the user to
the number of elements in the pname:pProperties array, and on return the
variable is overwritten with the number of structures actually written to
pname:pProperties.
If the value of pname:pPropertyCount is less than the number of display
planes for pname:physicalDevice, at most pname:pPropertyCount structures
will be written.

include::../../validity/protos/vkGetPhysicalDeviceDisplayPlanePropertiesKHR.txt[]

// refBegin VkDisplayPlanePropertiesKHR - Structure describing display plane properties

The sname:VkDisplayPlanePropertiesKHR structure is defined as:

include::../../api/structs/VkDisplayPlanePropertiesKHR.txt[]

  * pname:currentDisplay is the handle of the display the plane is currently
    associated with.
    If the plane is not currently attached to any displays, this will be
    sname:VK_NULL_HANDLE.
  * pname:currentStackIndex is the current z-order of the plane.
    This will be between 0 and the value returned by
    fname:vkGetPhysicalDeviceDisplayPlanePropertiesKHR() in
    pname:pPropertyCount.

include::../../validity/structs/VkDisplayPlanePropertiesKHR.txt[]

// refBegin vkGetDisplayPlaneSupportedDisplaysKHR - Query the list of displays a plane supports

To determine which displays a plane is usable with, call

include::../../api/protos/vkGetDisplayPlaneSupportedDisplaysKHR.txt[]

  * pname:physicalDevice is a physical device.
  * pname:planeIndex is the plane which the application wishes to use, and
    must: be in the range [eq]#[0, physical device plane count - 1]#.
  * pname:pDisplayCount is a pointer to an integer related to the number of
    displays available or queried, as described below.
  * pname:pDisplays is either `NULL` or a pointer to an array of
    sname:VkDisplayKHR handles.

If pname:pDisplays is `NULL`, then the number of displays usable with the
specified pname:planeIndex for pname:physicalDevice is returned in
pname:pDisplayCount.
Otherwise, pname:pDisplayCount must: point to a variable set by the user to
the number of elements in the pname:pDisplays array, and on return the
variable is overwritten with the number of handles actually written to
pname:pDisplays.
If the value of pname:pDisplayCount is less than the number of display
planes for pname:physicalDevice, at most pname:pDisplayCount handles will be
written.
If pname:pDisplayCount is smaller than the number of displays usable with
the specified pname:planeIndex for pname:physicalDevice, ename:VK_INCOMPLETE
will be returned instead of ename:VK_SUCCESS to indicate that not all the
available values were returned.

.Valid Usage
****
  * [[VUID-vkGetDisplayPlaneSupportedDisplaysKHR-planeIndex-01249]] pname:planeIndex must: be less than the number of display planes
    supported by the device as determined by calling
    fname:vkGetPhysicalDeviceDisplayPlanePropertiesKHR
****

include::../../validity/protos/vkGetDisplayPlaneSupportedDisplaysKHR.txt[]

Additional properties of displays are queried using specialized query
functions.


==== Display Modes

// refBegin VkDisplayModeKHR - Opaque handle to a display mode object

Display modes are represented by sname:VkDisplayModeKHR handles:

include::../../api/handles/VkDisplayModeKHR.txt[]

// refEnd VkDisplayModeKHR

// refBegin vkGetDisplayModePropertiesKHR - Query the set of mode properties supported by the display

Each display has one or more supported modes associated with it by default.
These built-in modes are queried by calling:

include::../../api/protos/vkGetDisplayModePropertiesKHR.txt[]

  * pname:physicalDevice is the physical device associated with
    pname:display.
  * pname:display is the display to query.
  * pname:pPropertyCount is a pointer to an integer related to the number of
    display modes available or queried, as described below.
  * pname:pProperties is either `NULL` or a pointer to an array of
    sname:VkDisplayModePropertiesKHR structures.

If pname:pProperties is `NULL`, then the number of display modes available
on the specified pname:display for pname:physicalDevice is returned in
pname:pPropertyCount.
Otherwise, pname:pPropertyCount must: point to a variable set by the user to
the number of elements in the pname:pProperties array, and on return the
variable is overwritten with the number of structures actually written to
pname:pProperties.
If the value of pname:pPropertyCount is less than the number of display
modes for pname:physicalDevice, at most pname:pPropertyCount structures will
be written.
If pname:pPropertyCount is smaller than the number of display modes
available on the specified pname:display for pname:physicalDevice,
ename:VK_INCOMPLETE will be returned instead of ename:VK_SUCCESS to indicate
that not all the available values were returned.

include::../../validity/protos/vkGetDisplayModePropertiesKHR.txt[]

// refBegin VkDisplayModePropertiesKHR - Structure describing display mode properties

The sname:VkDisplayModePropertiesKHR structure is defined as:

include::../../api/structs/VkDisplayModePropertiesKHR.txt[]

  * pname:displayMode is a handle to the display mode described in this
    structure.
    This handle will be valid for the lifetime of the Vulkan instance.
  * pname:parameters is a sname:VkDisplayModeParametersKHR structure
    describing the display parameters associated with pname:displayMode.

include::../../validity/structs/VkDisplayModePropertiesKHR.txt[]

// refBegin VkDisplayModeParametersKHR - Structure describing display parameters associated with a display mode

The sname:VkDisplayModeParametersKHR structure is defined as:

include::../../api/structs/VkDisplayModeParametersKHR.txt[]

  * pname:visibleRegion is the 2D extents of the visible region.
  * pname:refreshRate is a code:uint32_t that is the number of times the
    display is refreshed each second multiplied by 1000.

[NOTE]
.Note
====
For example, a 60Hz display mode would report a pname:refreshRate of 60,000.
====

include::../../validity/structs/VkDisplayModeParametersKHR.txt[]

// refBegin vkCreateDisplayModeKHR - Create a display mode

Additional modes may: also be created by calling:

include::../../api/protos/vkCreateDisplayModeKHR.txt[]

  * pname:physicalDevice is the physical device associated with
    pname:display.
  * pname:display is the display to create an additional mode for.
  * pname:pCreateInfo is a slink:VkDisplayModeCreateInfoKHR structure
    describing the new mode to create.
  * pname:pAllocator is the allocator used for host memory allocated for the
    display mode object when there is no more specific allocator available
    (see <<memory-allocation,Memory Allocation>>).
  * pname:pMode returns the handle of the mode created.

include::../../validity/protos/vkCreateDisplayModeKHR.txt[]

// refBegin VkDisplayModeCreateInfoKHR - Structure specifying parameters of a newly created display mode object

The sname:VkDisplayModeCreateInfoKHR structure is defined as:

include::../../api/structs/VkDisplayModeCreateInfoKHR.txt[]

  * pname:sType is the type of this structure.
  * pname:pNext is `NULL` or a pointer to an extension-specific structure.
  * pname:flags is reserved for future use, and must: be zero.
  * pname:parameters is a sname:VkDisplayModeParametersKHR structure
    describing the display parameters to use in creating the new mode.
    If the parameters are not compatible with the specified display, the
    implementation must: return ename:VK_ERROR_INITIALIZATION_FAILED.

.Valid Usage
****
  * [[VUID-VkDisplayModeCreateInfoKHR-width-01250]] The pname:width and pname:height members of the pname:visibleRegion
    member of pname:parameters must: be greater than `0`
  * [[VUID-VkDisplayModeCreateInfoKHR-refreshRate-01251]] The pname:refreshRate member of pname:parameters must: be greater than
    `0`
****

include::../../validity/structs/VkDisplayModeCreateInfoKHR.txt[]

// refBegin vkGetDisplayPlaneCapabilitiesKHR - Query capabilities of a mode and plane combination

Applications that wish to present directly to a display must: select which
layer, or "plane" of the display they wish to target, and a mode to use with
the display.
Each display supports at least one plane.
The capabilities of a given mode and plane combination are determined by
calling:

include::../../api/protos/vkGetDisplayPlaneCapabilitiesKHR.txt[]

  * pname:physicalDevice is the physical device associated with
    pname:display
  * pname:mode is the display mode the application intends to program when
    using the specified plane.
    Note this parameter also implicitly specifies a display.
  * pname:planeIndex is the plane which the application intends to use with
    the display, and is less than the number of display planes supported by
    the device.
  * pname:pCapabilities is a pointer to a
    slink:VkDisplayPlaneCapabilitiesKHR structure in which the capabilities
    are returned.

include::../../validity/protos/vkGetDisplayPlaneCapabilitiesKHR.txt[]

// refBegin VkDisplayPlaneCapabilitiesKHR - Structure describing capabilities of a mode and plane combination

The sname:VkDisplayPlaneCapabilitiesKHR structure is defined as:

include::../../api/structs/VkDisplayPlaneCapabilitiesKHR.txt[]

  * pname:supportedAlpha is a bitmask of
    elink:VkDisplayPlaneAlphaFlagBitsKHR describing the supported alpha
    blending modes.
  * pname:minSrcPosition is the minimum source rectangle offset supported by
    this plane using the specified mode.
  * pname:maxSrcPosition is the maximum source rectangle offset supported by
    this plane using the specified mode.
    The pname:x and pname:y components of pname:maxSrcPosition must: each be
    greater than or equal to the pname:x and pname:y components of
    pname:minSrcPosition, respectively.
  * pname:minSrcExtent is the minimum source rectangle size supported by
    this plane using the specified mode.
  * pname:maxSrcExtent is the maximum source rectangle size supported by
    this plane using the specified mode.
  * pname:minDstPosition, pname:maxDstPosition, pname:minDstExtent,
    pname:maxDstExtent all have similar semantics to their corresponding
    "Src" equivalents, but apply to the output region within the mode rather
    than the input region within the source image.
    Unlike the "Src" offsets, pname:minDstPosition and pname:maxDstPosition
    may: contain negative values.

The minimum and maximum position and extent fields describe the hardware
limits, if any, as they apply to the specified display mode and plane.
Vendors may: support displaying a subset of a swapchain's presentable images
on the specified display plane.
This is expressed by returning pname:minSrcPosition, pname:maxSrcPosition,
pname:minSrcExtent, and pname:maxSrcExtent values that indicate a range of
possible positions and sizes may: be used to specify the region within the
presentable images that source pixels will be read from when creating a
swapchain on the specified display mode and plane.

Vendors may: also support mapping the presentable images' content to a
subset or superset of the visible region in the specified display mode.
This is expressed by returning pname:minDstPosition, pname:maxDstPosition,
pname:minDstExtent and pname:maxDstExtent values that indicate a range of
possible positions and sizes may: be used to describe the region within the
display mode that the source pixels will be mapped to.

Other vendors may: support only a 1-1 mapping between pixels in the
presentable images and the display mode.
This may: be indicated by returning [eq]#(0,0)# for pname:minSrcPosition,
pname:maxSrcPosition, pname:minDstPosition, and pname:maxDstPosition, and
(display mode width, display mode height) for pname:minSrcExtent,
pname:maxSrcExtent, pname:minDstExtent, and pname:maxDstExtent.

These values indicate the limits of the hardware's individual fields.
Not all combinations of values within the offset and extent ranges returned
in sname:VkDisplayPlaneCapabilitiesKHR are guaranteed to be supported.
Vendors may: still fail presentation requests that specify unsupported
combinations.

include::../../validity/structs/VkDisplayPlaneCapabilitiesKHR.txt[]

ifdef::VK_EXT_display_control[]
include::../VK_EXT_display_control/display_control.txt[]
endif::VK_EXT_display_control[]

[[wsi-display-surfaces]]
=== Display Surfaces

// refBegin vkCreateDisplayPlaneSurfaceKHR - Create a slink:VkSurfaceKHR structure representing a display plane and mode

A complete display configuration includes a mode, one or more display planes
and any parameters describing their behavior, and parameters describing some
aspects of the images associated with those planes.
Display surfaces describe the configuration of a single plane within a
complete display configuration.
To create a sname:VkSurfaceKHR structure for a display surface, call:

include::../../api/protos/vkCreateDisplayPlaneSurfaceKHR.txt[]

  * pname:instance is the instance corresponding to the physical device the
    targeted display is on.
  * pname:pCreateInfo is a pointer to an instance of the
    slink:VkDisplaySurfaceCreateInfoKHR structure specifying which mode,
    plane, and other parameters to use, as described below.
  * pname:pAllocator is the allocator used for host memory allocated for the
    surface object when there is no more specific allocator available (see
    <<memory-allocation,Memory Allocation>>).
  * pname:pSurface points to a sname:VkSurfaceKHR handle in which the
    created surface is returned.

include::../../validity/protos/vkCreateDisplayPlaneSurfaceKHR.txt[]

// refBegin VkDisplaySurfaceCreateInfoKHR - Structure specifying parameters of a newly created display plane surface object

The sname:VkDisplaySurfaceCreateInfoKHR structure is defined as:

include::../../api/structs/VkDisplaySurfaceCreateInfoKHR.txt[]

  * pname:sType is the type of this structure.
  * pname:pNext is `NULL` or a pointer to an extension-specific structure.
  * pname:flags is reserved for future use, and must: be zero.
  * pname:displayMode is the mode to use when displaying this surface.
  * pname:planeIndex is the plane on which this surface appears.
  * pname:planeStackIndex is the z-order of the plane.
  * pname:transform is the transform to apply to the images as part of the
    scanout operation.
  * pname:globalAlpha is the global alpha value.
    This value is ignored if pname:alphaMode is not
    ename:VK_DISPLAY_PLANE_ALPHA_GLOBAL_BIT_KHR.
  * pname:alphaMode is the type of alpha blending to use.
  * pname:imageExtent The size of the presentable images to use with the
    surface.

[NOTE]
.Note
====
Creating a display surface must: not modify the state of the displays,
planes, or other resources it names.
For example, it must: not apply the specified mode to be set on the
associated display.
Application of display configuration occurs as a side effect of presenting
to a display surface.
====

.Valid Usage
****
  * [[VUID-VkDisplaySurfaceCreateInfoKHR-planeIndex-01252]] pname:planeIndex must: be less than the number of display planes
    supported by the device as determined by calling
    fname:vkGetPhysicalDeviceDisplayPlanePropertiesKHR
  * [[VUID-VkDisplaySurfaceCreateInfoKHR-planeReorderPossible-01253]] If the pname:planeReorderPossible member of the
    sname:VkDisplayPropertiesKHR structure returned by
    fname:vkGetPhysicalDeviceDisplayPropertiesKHR for the display
    corresponding to pname:displayMode is ename:VK_TRUE then
    pname:planeStackIndex must: be less than the number of display planes
    supported by the device as determined by calling
    fname:vkGetPhysicalDeviceDisplayPlanePropertiesKHR; otherwise
    pname:planeStackIndex must: equal the pname:currentStackIndex member of
    sname:VkDisplayPlanePropertiesKHR returned by
    fname:vkGetPhysicalDeviceDisplayPlanePropertiesKHR for the display plane
    corresponding to pname:displayMode
  * [[VUID-VkDisplaySurfaceCreateInfoKHR-alphaMode-01254]] If pname:alphaMode is ename:VK_DISPLAY_PLANE_ALPHA_GLOBAL_BIT_KHR then
    pname:globalAlpha must: be between `0` and `1`, inclusive
  * [[VUID-VkDisplaySurfaceCreateInfoKHR-alphaMode-01255]] pname:alphaMode must: be `0` or one of the bits present in the
    pname:supportedAlpha member of sname:VkDisplayPlaneCapabilitiesKHR
    returned by fname:vkGetDisplayPlaneCapabilitiesKHR for the display plane
    corresponding to pname:displayMode
  * [[VUID-VkDisplaySurfaceCreateInfoKHR-width-01256]] The pname:width and pname:height members of pname:imageExtent must: be
    less than the pname:maxImageDimensions2D member of
    sname:VkPhysicalDeviceLimits
****

include::../../validity/structs/VkDisplaySurfaceCreateInfoKHR.txt[]

// refBegin VkDisplayPlaneAlphaFlagBitsKHR - Alpha blending type

Types of alpha blending supported by or used on a display are defined by the
bitmask ename:VkDisplayPlaneAlphaFlagBitsKHR, which contains the following
values:

include::../../api/enums/VkDisplayPlaneAlphaFlagBitsKHR.txt[]

These values are described as follows:

  * ename:VK_DISPLAY_PLANE_ALPHA_OPAQUE_BIT_KHR: The source image will be
    treated as opaque.
  * ename:VK_DISPLAY_PLANE_ALPHA_GLOBAL_BIT_KHR: A global alpha value must:
    be specified that will be applied to all pixels in the source image.
  * ename:VK_DISPLAY_PLANE_ALPHA_PER_PIXEL_BIT_KHR: The alpha value will be
    determined by the alpha channel of the source image's pixels.
    If the source format contains no alpha values, no blending will be
    applied.
    The source alpha values are not premultiplied into the source image's
    other color channels.
  * ename:VK_DISPLAY_PLANE_ALPHA_PER_PIXEL_PREMULTIPLIED_BIT_KHR: This is
    equivalent to ename:VK_DISPLAY_PLANE_ALPHA_PER_PIXEL_BIT_KHR except the
    source alpha values are assumed to be premultiplied into the source
    image's other color channels.

// refEnd VkDisplayPlaneAlphaFlagBitsKHR