I'm creating a relatively complex nav layout for a single-page scrolling site using GSAP and ScrollMagic. The "upcoming" page in the navigation tweens upward as you scroll down until it hits the top of the nav, and then a page transition is triggered (which is unrelated to this issue). I've included a stripped-down Codepen with only the Nav - please view it in Full View using Chrome or Firefox to see the effect working properly.
The value it's tweening to achieve that effect is relatively complicated - it's top: calc(-100vh + [nav container height] + [2x nav bottom property]) which has the effect of moving each item up but maintaining the same spacing once they're stacked at the top. I know there's an outstanding issue with tweening calc() values that's been on GitHub for a while - you can't tween them unless you first use TweenMax.set to establish the pre-tween calc value. Using that workaround got it to work in Chrome and Firefox, but it's still not working in Safari. Instead Safari waits until the end of the ScrollMagic duration and then simply jumps to the end value.
I'm not sure what to do about this issue - I've tested it in Safari and tweening a non-calc value works fine, but I need a calc in order to achieve the effect I want. Any help would be appreciated!