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LockAsync routine

The LockAsync function locks the specified resource or a surface within the resource.

Syntax


PFND3DDDI_LOCKASYNC LockAsync;

__checkReturn HRESULT APIENTRY LockAsync(
  _In_     HANDLE hDevice,
  _Inout_  D3DDDIARG_LOCKASYNC *pData
)
{ ... }

Parameters

hDevice [in]

A handle to the display device (graphics context).

pData [in, out]

A pointer to a D3DDDIARG_LOCKASYNC structure that describes the resource or surface within the resource to lock.

Return value

LockAsync returns one of the following values:

Return codeDescription
S_OK

The resource is successfully locked.

E_OUTOFMEMORY

LockAsync could not allocate the required memory for it to complete.

D3DDDIERR_WASSTILLDRAWING

Renaming the allocation that corresponds to the resource that the D3DDDIARG_LOCKASYNC structure specifies failed.

The driver returns this value only if the Discard bit-field flag was set in the Flags member of D3DDDIARG_LOCKASYNC.

E_NOTIMPL

The user-mode display driver does not support LockAsync for the specified resource.

 

Remarks

On multiple-processor computers, the Microsoft Direct3D runtime might call most functions of the user-mode display driver from a worker thread instead of from the main application thread. This multiple-processor optimization is transparent to the user-mode display driver. When the runtime uses multiple-processor optimization, it might call LockAsync rather than the Lock function to lock a resource.

A user-mode display driver optionally implements LockAsync; the Direct3D runtime calls LockAsync only if the driver implements the LockAsync, UnlockAsync, and Rename functions. However, a user-mode display driver should implement LockAsync and the UnlockAsync and Rename functions because applications that frequently lock dynamic resources can then achieve higher performance.

When the Direct3D runtime uses multiple-processor optimization, it calls most user-mode display driver functions from a worker thread that the runtime manages; however, the runtime calls LockAsync on the application's main thread.

If a user-mode display driver exposes a DDI version of 0x0000000B or greater (the driver returns this value in the DriverVersion member of the D3D10DDIARG_OPENADAPTER structure in a call to the driver's OpenAdapter function), the Direct3D runtime will call LockAsync in a reentrant manner. When the runtime calls LockAsync in a reentrant manner, one thread can execute inside LockAsync while another thread that references the same display device executes inside of another user-mode display driver function. Additionally, on this type of driver, the runtime will call LockAsync for system memory surfaces. If the Discard bit-field flag is set in the Flags member of D3DDDIARG_LOCKASYNC, the driver should attempt to rename the allocation that corresponds to the resource. Typically, to rename an allocation, the driver calls the pfnLockCb function with the allocation handle that corresponds to the resource to be locked.

The driver should set the Discard bit-field flag in the Flags member of the D3DDDICB_LOCK structure when the driver calls pfnLockCb. The driver should set the NoExistingReference bit-field flag of D3DDDICB_LOCK when the driver calls pfnLockCb only if the NoExistingReferences bit-field flag is set to TRUE in the Flags member of D3DDDIARG_LOCKASYNC, and the driver has no internally queued references to the resource.

If the driver fails to rename the allocation, the driver's LockAsync function should return the failure back to the runtime, and the driver should not flush its command buffer. If the renaming succeeds, the driver should return pointers to resource memory, pitch, and slice pitch and a handle to the resource that represents the renamed allocation in the members of D3DDDIARG_LOCKASYNC. The driver should not update its internal tracking structures with the new allocation handle that pfnLockCb returns. Instead, the driver should wait until its Rename function is called.

If the NoOverwrite bit-field flag is set in the Flags member of D3DDDIARG_LOCKASYNC, the driver should lock the corresponding allocation with no-overwrite semantics. The driver should call pfnLockCb with the IgnoreSync bit-field flag set in the Flags member of D3DDDICB_LOCK and should then return pointers to resource memory, pitch, and slice pitch to the Direct3D runtime in the members of D3DDDIARG_LOCKASYNC. If the driver returns success (S_OK) from a call to its LockAsync with the NoOverwrite bit-field flag set, it might be called to render with a locked surface. The driver should return success from a call to its LockAsync with NoOverwrite set only for surfaces that can be rendered while locked. The video memory manager requires that the allocations that correspond to the surfaces must be supported in AGP or aperture segments; otherwise, calls to the pfnRenderCb function fail when the command buffer references a locked allocation.

In summary, the driver should fail calls to its LockAsync function if renaming fails or if no-overwrite semantics are not supported for the resource. However, the Direct3D runtime will recover from these failures. For all other situations, drivers should return success from LockAsync to improve performance on multiple-processor computers.

Requirements

Version

Available in Windows Vista and later versions of the Windows operating systems.

Header

D3dumddi.h (include D3dumddi.h)

See also

CreateResource
D3DDDI_DEVICEFUNCS
D3DDDIARG_CREATERESOURCE
D3DDDIARG_LOCKASYNC
D3DDDICB_LOCK
Lock
pfnLockCb
pfnRenderCb
Rename
UnlockAsync

 

 

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