SliverFlexibleHeader proposal

[marcoredz]

This new widget should allows to create a Sliver header that can be pinned or floating based on a parameter without knowing the size of its child.

Demo:

sliver_flexible_header.mp4

[JasCodes]

@Kavantix Whats holding this back?

[JasCodes]

@marcoredz Doesn't work in Sliver Stack btw

cc @Kavantix

[Kavantix]

@marcoredz sorry for the late reply, have been swamped again.
But thanks for the contribution!
In general the implementation looks good although I'm not sure if it handles the overlap correctly in all cases.
Could you add some tests for a few simple cases and some overlap cases.

For the API of the package it would make more sense to have a SliverFloatingHeader widget that is always floating since there is already a SliverPinnedHeader

[Kavantix]

Could you add some tests for a few simple cases and some overlap cases.

For the API of the package it would make more sense to have a SliverFloatingHeader widget that is always floating since there is already a SliverPinnedHeader

[marcoredz]

Apologies for the delayed response, @Kavantix. My proposal was based on this gist: https://gist.github.com/tomaszpolanski/cf0edb7961d2304c2f293da9971cd4c9.

Unfortunately, I am currently unable to proceed with working on this proposal. Therefore, if you or someone else can find a way to incorporate this feature into the package, it would be awesome. Otherwise, it's not a problem for me if you decide to close the PR.

Edit: I totally agree with your API naming suggestion and functionality, so the floating parameter could be removed.