The child provided to decorator functions is larger than it should be

[benthillerkus]

Bug report

Describe the bug

With the decorator argument on WoltModalSheet.show you can provide a Widget tree in which the modal sheet will essentially be embedded as a child.
I want to use the decorator to add a blurred background to the sheet.
Unfortunately, the child provided to the decorator function is always as large as maxPageHeight, so when I wrap it with a BackdropFilter and a ClipRRect, I will essentially have a large blank blurred space on top of my sheet if the sheet resizes itself to be smaller than maxPageHeight.

Steps to reproduce

...
WoltModalSheet.show(
  ...
  decorator: (child) {
    return Align(
      alignment: Alignment.bottomCenter,
      child: ClipRRect(
        ...
        child: BackdropFilter(
          ...
          child: child,
        )
      )
    )
  }
  ...
)

Expected behavior

I'd expect child to be only as large as the area that it paints with content.

[benthillerkus]

Oh, no, looking at the code, I think this is because CustomMultiChildLayout just always takes as much space as it can get, right?

I think fixing this would require using CustomBoxy from the boxy package, because with that layout widget, you can actually have the size of the parent depend on the size of the children.

[benthillerkus]

That or, move the decorator function to wrap a smaller part of the tree, ie a part that is being laid out by the CustomMultiChildLayout

[ulusoyca]

Thanks for the contribution and the PR 💙 Closing this since your PR is merged.