@jiub @ShadowJonathan mine was a physical button under my desk, in the form of a cheap KVM. Because occasionally the i915 driver would just fail to buffer swap for one reason or another, so the output stuck on the last displayed frame, and gnome would never retry it. Give it a kick by unplugging and re-plugging the monitors and it came right back. With such a cheap KVM, switching inputs is roughly equivalent to just yanking the cords out of the back of the machine, so it did the job just fine without needing to reach down and interact with the actual box.