Gamma, contrast, brightness resetting immediately

[IronMew]

It used to be that I could modify these ingame, and alt-tabbing would get me a *very* bright Windows desktop. This wasn't as annoying as it sounds because GZDoom loads so fast I'd just save, quit, do what I needed to do, restart and reload in less time it takes many modern games to alt-tab.

Now I just ran GZDoom (1.7.1) again after quite a while, and I can no longer modify those settings. If I do they'll stick for about a second, then everything returns to default. The slider remains at the new setting, but it has no effect.

Alt-tabbing gives me a normally-lit Windows desktop, so I get the feeling Windows is overriding the settings in the game.

How can I fix this so I can change the settings again and not have them reset immediately? I'm tired of not seeing where I'm going.

[Graf Zahl]

Has anything changed about your system. This looks indeed like a system-side problem. Unfortunately I can't do much about it. Windows has always been treating OpenGL as a second class citizen.

[IronMew]

I certainly changed things from the last time I played Doom, but I don't recall changing anything explicitly related to gamma, contrast and such. Not sure if something else changed stuff.
What system settings should I be looking for?

[Graf Zahl]

Most importantly the graphics driver. It's ultimately responsible for applying the data.