Gamma correction is done via dotsTheScreen. See the comments for dotsTheScreen.makeGammaTable for more details.
Some references about what this is and why it is important: [Cambridge website] [Brainard paper]

snow-dots/utilities/benchmarks/benchmarkMonitorLuminance: Measure the luminance of a spot on your monitor using the optiCAL device.

snow-dots/utilities/benchmarks/benchmarkMonitorTiming: measure monitor timing using a photodiode.

snow-dots/utilities/benchmarks/benchmarkGraphicsTiming: measure how much graphics processing the machine can do without skipping frames.