Multi-Monitors Need To Keep Offsets When Controlling With Hotkeys

[ToyburgBob]

Monitors have different brightness levels. Once they all are set to be a relative brightness, using hotkeys to increase or decrease should not change the relationship of brightness between the monitors. E.g. Hotkeys changing all three monitors at once. Mon#1 reaches 100% well before Mon#3 does. Then decreasing Mon#1 should not start decreasing until Mon#3 reaches the original setting.