stimuli rendering input-registration report event eye-tracking proxy-variable snippet randomization mouse button timing audio add-video-links license color renderer-element rgb gui library sublayer proxy windows10 elo cueing posners arrow proxy-variable-proxy processing-shimmer alerter implicit photometer temporal-frequency gratings 2afc neurofeedback digital-lines national-instruments save-image gdi-canvas association ni-tracker faq linked-video videoplayer lag gif calibration eyelink video-priority usb email video-player rating web-browser survey psychophysics slider blur roulette screen-cloning status-screen radar key signal touch luminance equalizing error hardware material trial monitor display layers&flow eeg synchronization dva gaussian gabor template variable layer runtime logging task test