If you need non jerkiness, players just have to understand, that the description "DirectX Fullscreen Exclusive" is not just some PR gag ... either they want their game to get the exclusive focus of the OS with the resulting high performance or if they want other stuff doing at the same time which depending on what it is (most likely: if it uses 3D even if not active like having a movie capable media player running and the like) and with the consequences of this step.
After all, fullscreen ex isn't just for fun, windowed on the other end, never was meant for "full realtime" stuff ... So easiest is to restrict the windowed usage to the point where a max of X flips is done per second (60? Screen hz / 2 or in worst case even /3 ) so the app can't get jerky. This could be handled by some simple checks, for example if the average runtime of the mainloop has serious differences etc.
Just as a small example: Having iTunes running at the same time will nearly guarantee ANY game to start get jerky (even with dual core it is somehow able to impact the whole system. With some other apps running at the same time it can even hardlock the OS)
After all, fullscreen ex isn't just for fun, windowed on the other end, never was meant for "full realtime" stuff ... So easiest is to restrict the windowed usage to the point where a max of X flips is done per second (60? Screen hz / 2 or in worst case even /3 ) so the app can't get jerky. This could be handled by some simple checks, for example if the average runtime of the mainloop has serious differences etc.
Just as a small example: Having iTunes running at the same time will nearly guarantee ANY game to start get jerky (even with dual core it is somehow able to impact the whole system. With some other apps running at the same time it can even hardlock the OS)