PC games that don't use Raw Input or DirectInput are showing severe mouse lag.
A post on Reddit reveals that many PC gamers are experiencing mouse lag issues with some titles after upgrading to Windows 8.1. This lag reportedly stems from a change in handling DPI for multiple monitors, and affects a number of PC games including Deus Ex: Human Revolution, S.T.A.L.K.E.R.: Call of Pripyat, Metro 2033 and several Call of Duty titles.
According to the post, changes in the DPI framework have caused games that don't use Raw Input or DirectInput to suffer large amounts of mouse lag. The lag also seems to affect PC gamers that use high DPI mice and high polling-rate mice more than users who use basic hardware. The problem may also affect players with mice that have on-board memory.
"Something about Window's relationship with your mouse has been altered (specifically, the Multi DPI improvement for multiple monitors) and this causes those games that don't read raw mouse data to become close-to unplayable," the post reads. "I stumbled upon this issue because it affects two games I'm trying to play through right now."
For now, a way to possibly fix the mouse issue is to right-click on the EXE of the game in question, go to Properties, go to the Compatibility tab, and check "run this program in compatibility mode for" and select "Windows 8." Also check "disable scaling of high DPI settings" and check "run this program as an administrator." This method may or may not solve the problem.
"It is real lag," states Mark Cranness, the creator of the MarkC mouse fix. "[It] affects games that don't use Raw Input (or DirectInput, which is more-or-less the same thing) for reading the mouse. When I first saw this lag in 8.1, I improved the debug detail of the recording tool a lot, to see if that might help explain what was happening. The improvements clearly showed lag between mouse movement happening and Windows updating the pointer position. Seeing that it IS a problem is as far as I've gone so far in diagnosing it."
He also said that the EXE fix mentioned above doesn't affect his recording tool: the software still shows lag. So far Microsoft has not responded to the reports, so stay tuned.