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IDCompositionTexture::GetAvailableFence method (dcomp.h)

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Retrieves a Direct3D synchronization fence/value pair that indicates when the composition texture will become available, if that info is known. The value returned depends on the availability state of the composition texture. An availability state specifies whether, and when, it's safe to render to the composition texture.

See the Remarks section for the availability states, their descriptions, and how GetAvailableFence behaves for each state.

If a composition texture becomes available, then your app must be careful to issue rendering only to the exact subregion of the Direct3D texture that it refers to.

Syntax

HRESULT GetAvailableFence(
  UINT64 *fenceValue,
  REFIID iid,
  void   **availableFence
);

Parameters

fenceValue

Type: _Out_ UINT64*

The returned fence value.

iid

Type: _In_ REFIID

An interface identifier.

availableFence

Type: _Outptr_result_maybenull_ void**

The returned available fence, or nullptr, depending on the availability state of the composition texture. For details, see the Remarks section.

Return value

Type: HRESULT

If the function succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.

Remarks

Here are the availability states, their descriptions, and how GetAvailableFence behaves for each state.

immediately available. The composition texture isn't being displayed by the desktop window manager (DWM), nor are application commits queued to have it do so. So the composition texture is safe to write to immediately. GetAvailableFence returns the available fence, which will already match the returned value.

soon-to-be available. The composition texture is currently being displayed by DWM, but the application has removed it from its visual tree, and committed to DWM. However, that commit hasn't yet been processed by DWM, so DWM hasn't yet stopped displaying the texture. Your app can render to a soon-to-be available texture if that work is synchronized against the texture’s available fence. GetAvailableFence returns the available fence. The composition texture will be safe to write to when that fence is signaled to the returned value.

unavailable. The composition texture is currently being displayed by DWM, or it's queued for display by DWM. So your app shouldn't write to it. GetAvailableFence returns nullptr instead of a fence.

The available fence describes the availability of a single composition texture. Multiple composition textures might reference the same Direct3D texture, if each composition texture takes a different (non-overlapping) region of the larger Direct3D texture by specifying a source rect (a technique known as atlasing). In a case like that, if a composition texture becomes available, then your app must be careful to issue rendering only to the exact subregion of the Direct3D texture; to make sure not to interfere with pixels that might belong to other composition textures (which might not be available). That's because different regions of a single Direct3D texture might have different availability states.

Requirements

Requirement Value
Header dcomp.h

See also