Passing DXGI Information at Resource Creation Time
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Passing DXGI Information at Resource Creation Time

The Direct3D version 10 runtime can pass DXGI-specific information when it calls the user-mode display driver's CreateResource(D3D10) function to create a resource. The runtime can pass a pointer to a DXGI_DDI_PRIMARY_DESC structure in the pPrimaryDesc member of the D3D10DDIARG_CREATERESOURCE structure to specify that the resource can be used as a primary (that is, the resource can be scanned out to the display). The runtime sets pPrimaryDesc to a non-NULL value only if the runtime also sets the D3D10_DDI_BIND_PRESENT bit in the BindFlags member of D3D10DDIARG_CREATERESOURCE.

The runtime can specify the DXGI_DDI_PRIMARY_OPTIONAL flag in the Flags member of DXGI_DDI_PRIMARY_DESC to notify the user-mode display driver that the driver can opt out from using the resource in a flip-style presentation. To notify the runtime that it should not use the resource in flip-style presentations, the driver sets the DXGI_DDI_PRIMARY_DRIVER_FLAG_NO_SCANOUT flag in the DriverFlags member of DXGI_DDI_PRIMARY_DESC.

If the driver returns DXGI_DDI_PRIMARY_DRIVER_FLAG_NO_SCANOUT in the CreateResource(D3D10) call to create the resource, the runtime will always perform a bit-block transfer (bitblt)-style presentation (instead of a flip-style presentation) when the resource is the source of the presentation. This functionality is useful if graphics hardware cannot scan out a particular subset of a given resource type. For example, graphics hardware might or might not be able to scan out a multisampled back buffer type of resource. In addition, the ability to scan out multisampled back buffers might further depend on the format of the surface. If the graphics hardware was not able to scan out a particular multisampled format, the user-mode display driver would set the DXGI_DDI_PRIMARY_DRIVER_FLAG_NO_SCANOUT flag in the DriverFlags member of DXGI_DDI_PRIMARY_DESC for the resource with this format.

If the runtime does not set the DXGI_DDI_PRIMARY_OPTIONAL flag in the Flags member of DXGI_DDI_PRIMARY_DESC to notify the driver about the possibility of opting out of using the resource in a flip-style presentation, the driver can still return the DXGI_DDI_ERR_UNSUPPORTED error code along with the DXGI_DDI_PRIMARY_DRIVER_FLAG_NO_SCANOUT flag from a call to CreateResource(D3D10). The driver's CreateResource(D3D10) passes DXGI_DDI_ERR_UNSUPPORTED in a call to the pfnSetErrorCb function if the driver cannot scan out such a primary. Returning DXGI_DDI_ERR_UNSUPPORTED along with DXGI_DDI_PRIMARY_DRIVER_FLAG_NO_SCANOUT causes DXGI to interpose a proxy surface in the presentation path, between the back buffers and the primary surface. The proxy surface always matches the primary (scanned-out) surface in terms of size, multisample, and rotation. The first step in this process is for DXGI to determine which of the multisample or rotation settings cause the driver to refuse to scan out a surface with those settings. DXGI makes this determination by scaling back and trying to create a primary without rotation, without multisampling, or without both. After DXGI determines the driver's support for scan-out features, DXGI creates the primary and proxy surfaces, and the driver should be able to flip between these two surfaces. DXGI will still subsequently satisfy an application's requests for auto-rotated or multisampled back buffers by calling the driver's BltDXGI function to perform bitblts from back buffers to the proxy surface. These bitblts request the driver to perform multisample resolves or rotates. For more information about BltDXGI, see the BltDXGI reference page.



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