This method reports the current cooperative-level status of the Microsoft® Direct3D Mobile® device for a windowed or full-screen application.
If the device is lost but cannot be restored at the current time, IDirect3DMobileDevice::TestCooperativeLevel returns the D3DMERR_DEVICELOST return code. This would be the case, for example, when a full-screen device has lost focus. If an application detects a lost device, it should pause and periodically call IDirect3DMobileDevice::TestCooperativeLevel until it receives a return value of D3DMERR_DEVICENOTRESET.
The application may then attempt to reset the device by calling IDirect3DMobileDevice::Reset and, if this succeeds, restoring the necessary resources and resume normal operation. Note that IDirect3DMobileDevice::Present will return D3DMERR_DEVICELOST if the device is either "lost" or "not reset."
A call to IDirect3DMobileDevice::TestCooperative Level will fail if called on a different thread than that used to create the device being reset.