PR#28396 originally addressed an update via issue #23983 to make images more visible with a white background (implementation of gray "lightbox").
This PR implements those styles defined in PR#28396.
PR Close#33259
Not mentioned in the docs.
Whenever offset property is used inside a keyframe's step at least once, then it must be defined to all the steps.
When read the first time, I supposed that the API automatically sets an even offset to the remaining not defined offsets, which is not
PR Close#32350
