Direct3D9 cannot access the GPU when minimizing or locking the screen, even without a display monitor hardware. Is here a resolution to let Direct3D9 work even no display monitor is connected with machine. For example, create a software display monitor or hook some logics? I don't know.
Thanks for your help.
I try to convert Direct3D9 to Direct3D9Ex to let it work. But some formats of memory pool are not supported in Direct3D9Ex.