1. A method for switching from using a first graphics-processing unit (GPU) to using a second GPU to drive a display, comprising: using a first thread to execute a window manager that performs operations associated with servicing user requests; receiving a request to switch from using the first GPU to using the second GPU as a signal source for driving the display; and in response to the request, using a second thread to configure the second GPU in preparation for driving the display, while the second thread is configuring the second GPU, continuing to use the first thread to execute the window manager to service user requests, and after configuration of the second GPU is complete, switching the signal source which drives the display from the first GPU to the second GPU.