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IddCx Objects

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The IddCx (Indirect Display Driver Class eXtension) uses the extensible UMDF object model to represent the components of the indirect display device. The UMDF object model allows the driver-specific storage to be associated with each IddCx (and hence UMDF) object. See UMDF Object Model for more information.

The order in which IDD objects are created is:

  • The driver first creates an IDDCX_ADAPTER object.
  • The driver then creates an IDDCX_MONITOR object.
  • Once the IDDCX_ADAPTER and IDDCX_MONITOR objects are created, the OS creates IDDCX_SWAPCHAIN and IDDCX_OPMCTX objects and sends them to the driver.

The following sections provide more details about these objects.

IDDCX_ADAPTER

This object represents a single logical display adapter created by the driver in a two stage process:

The IDD model does not have an explicit destroy adapter callback. Once the adapter initialization sequence has been completed successfully, the adapter is valid until the UMDF device passed at initialization time is stopped. When creating the adapter, the driver provides static adapter information about the indirect display adapter.

Handling multifunction devices

In the simplest case, there is a one-to-one mapping between the UMDF device object created by the plug and play subsystem for the attached indirect display device and the IDDCX_ADAPTER object that the indirect display driver (IDD) creates.

There can be more complex scenarios where a single indirect display dongle contains multiple plug and play devices. For example, an indirect display solution might have multiple PnP device functions such as a microphone (audio driver) and camera (video driver). In such situations, it is the IDD's responsibility to create a single IDDCX_ADAPTER object for the multiple UMDF device objects created for each PnP device. The driver needs to consider the following in this scenario:

  • The IDDCX_ADAPTER should only be created once all the PnP devices that make up the indirect display solution have been started successfully.
  • The driver must pass a single WDFDEVICE when creating the adapter, so it requires logic to decide which UMDF device it will pass.
  • If any of the devices that make up the indirect display adapter have a hardware error, the driver should report all devices that make up the adapter as being in error.

IDDCX_MONITOR

This object represents a specific monitor connected to one of the connectors on the indirect display adapter.

The driver creates the monitor object in a two stage process:

When a monitor is unplugged, the driver calls the IddCxMonitorDeparture callback to report the monitor has been unplugged, which causes the IDDCX_MONITOR object to be destroyed. Even if the same monitor is un-plugged then reconnected, the IddCxMonitorDeparture/IddCxMonitorArrival sequence needs to be called again.

The IDDCX_MONITOR is a child of the IDDCX_ADAPTER object.

IDDCX_SWAPCHAIN

This object represents a swapchain that will provide desktop images to display on a connected monitor. The swapchain has multiple buffers to allow the OS to compose the next desktop image in one buffer while the IDD is accessing another buffer. The IDDCX_SWAPCHAIN is a child of the IDDCX_MONITOR so there will only be one assigned swapchain to a given monitor at any time.

The OS creates and destroys the IDDCX_SWAPCHAIN objects and assigns/unassigns them to monitors using the EvtIddCxMonitorAssignSwapChain and EvtIddCxMonitorUnassignSwapChain Ddi calls.

IDDCX_OPMCTX

This object represents an active Output Protection Manager (OPM) context from a single application OPM context that the application can use to control output protection on a single monitor. Multiple OPM contexts can be active on a given monitor at the same time. The OS calls the driver to create and destroy the OPM contexts using the driver's EvtIddCxMonitorOPMCreateProtectedOutput and EvtIddCxMonitorOPMDestroyProtectedOutput DDI calls.