GetDisplayConfigBufferSizes function (winuser.h)

Article
03/26/2022

The GetDisplayConfigBufferSizes function retrieves the size of the buffers that are required to call the QueryDisplayConfig function.

Syntax

LONG GetDisplayConfigBufferSizes(
  [in]  UINT32 flags,
  [out] UINT32 *numPathArrayElements,
  [out] UINT32 *numModeInfoArrayElements
);

Parameters

[in] flags

The type of information to retrieve. The value for the Flags parameter must be one of the following values.

QDC_ALL_PATHS

The caller requests the table sizes to hold all the possible path combinations.

QDC_ONLY_ACTIVE_PATHS

The caller requests the table sizes to hold only active paths.

QDC_DATABASE_CURRENT

The caller requests the table sizes to hold the active paths as defined in the persistence database for the currently connected monitors.

[out] numPathArrayElements

Pointer to a variable that receives the number of elements in the path information table. The pNumPathArrayElements parameter value is then used by a subsequent call to the QueryDisplayConfig function. This parameter cannot be NULL.

[out] numModeInfoArrayElements

Pointer to a variable that receives the number of elements in the mode information table. The pNumModeInfoArrayElements parameter value is then used by a subsequent call to the QueryDisplayConfig function. This parameter cannot be NULL.

Return value

The function returns one of the following return codes.

Return code	Description
ERROR_SUCCESS	The function succeeded.
ERROR_INVALID_PARAMETER	The combination of parameters and flags that are specified is invalid.
ERROR_NOT_SUPPORTED	The system is not running a graphics driver that was written according to the Windows Display Driver Model (WDDM). The function is only supported on a system with a WDDM driver running.
ERROR_ACCESS_DENIED	The caller does not have access to the console session. This error occurs if the calling process does not have access to the current desktop or is running on a remote session.
ERROR_GEN_FAILURE	An unspecified error occurred.

Remarks

Given the current display path configuration and the requested flags, GetDisplayConfigBufferSizes returns the size of the path and mode tables that are required to store the information. GetDisplayConfigBufferSizes can return values that are slightly larger than are actually required because it determines that all source and target paths are valid; whereas, the driver might place some restrictions on the possible combinations.

As GetDisplayConfigBufferSizes can only determine the required array size of that moment in time, it is possible that between calls to GetDisplayConfigBufferSizes and QueryDisplayConfig the system configuration has changed and the provided array sizes are no longer sufficient to store the new path data.

If a caller is aware that it must enable additional sources and targets, the caller can allocate a larger mode information array than is returned from GetDisplayConfigBufferSizes so that it has the space to add the additional source and target modes after calling QueryDisplayConfig and before calling SetDisplayConfig.

Examples

See QueryDisplayConfig for an example of GetDisplayConfigBufferSizes.

Requirements

Requirement	Value
Minimum supported client	Available in Windows Vista and later versions of the Windows operating systems.
Target Platform	Universal
Header	winuser.h (include Windows.h)
Library	User32.lib; OneCoreUAP.lib on Windows 10
DLL	User32.dll
API set	ext-ms-win-ntuser-sysparams-ext-l1-1-1 (introduced in Windows 10, version 10.0.14393)