The XR_MSFT_secondary_view_configuration extension.

This extension allows an application to enable support for one or more secondary view configurations. A secondary view configuration is a well-known set of views that the runtime can make active while a session is running. In a frame where a secondary view configuration is active, the application’s single frame loop should additionally render into those active secondary views, sharing the frame waiting logic and update loop with the primary view configuration for that running session.

A proper secondary view configuration support includes following steps:

• When calling CreateInstance, enable the XR_MSFT_secondary_view_configuration extension and the extension defines a concrete secondary view configuration type, for example, XR_MSFT_first_person_observer.
• Inspect supported secondary view configurations using the EnumerateViewConfigurations function.
• Enable supported secondary view configurations using the BeginSession function with an XrSecondaryViewConfigurationSessionBeginInfoMSFT chained extension structure.
• Inspect if an enabled secondary view configuration is activated by the system or the user using the WaitFrame function with an XrSecondaryViewConfigurationFrameStateMSFT chained extension structure.
• When a secondary view configuration is changed to active, get the latest view configuration properties using the GetViewConfigurationProperties and EnumerateViewConfigurationViews functions.
• Create the swapchain images for the active secondary view configuration using the CreateSwapchain function with an XrSecondaryViewConfigurationSwapchainCreateInfoMSFT chained extension structure using recommendedImageRectWidth and recommendedImageRectHeight in the corresponding XrViewConfigurationView structure returned from EnumerateViewConfigurationViews.
• Locate the secondary view configuration views using the LocateViews function with the active secondary view configuration type.
• Submit the composition layers using the swapchain images for an active secondary view configuration using the EndFrame function with the XrSecondaryViewConfigurationFrameEndInfoMSFT chained extension structure.