feat: Support additional custom offset in case of pinned header above…

[Ortes]

No breaking change (I think)
Add support for addition custom offset.

.scrollToIndex() now takes an additional nullable offset parameter which move the final offset by this amount.

[jerrywell]

Hi @Ortes,

This feature can actually be achieved using an alternative method.

e.g.

await scrollController.scrollToIndex(10);
await scrollController.animateTo(scrollController.offset + [Offset], ...);

since the underlying implementation works the same way. : )

[Ortes]

Indeed it works but it does not have the exact same behavior because it scroll to the offset then backward (I put negative values because I have a pinned header above so I need to offset negatively)

[jerrywell]

Sorry for the late response; there was a permission issue with this repo.

Regarding your case with the pinned header, is viewportBoundaryGetter sufficient for your needs?
You can refer to this README and search for this term.

We are trying to keep the number of arguments in the interface as minimal as possible to maintain simplicity for everyone.