GetBrightness
BPrivateScreen::GetBrightness(float* brightness)
BScreen::GetBrightness(float* brightness)
BitmapHWInterface::GetBrightness(float*)
AccelerantHWInterface::GetBrightness(float* brightness)
RemoteHWInterface::GetBrightness(float*)
DWindowHWInterface::GetBrightness(float* brightness)
ViewHWInterface::GetBrightness(float* brightness)