Shaun HarrisonIs it documented anywhere that #SwiftUI's background(_:in:) API implicitly calls containerShape, even prior to 26?
This still seems totally unexpected to me
https://developer.apple.com/documentation/swiftui/view/background(_:in:fillstyle:)
I was only able to "confirm" the implicit containerShape call by explicitly setting a containerShape before calling background(_:in:)
Everything I've searched (and Claude) tells me this shouldn't be happening and it should require explicit containerShape or ConcentricRectangle/ContainerRelativeShape
robb@shnhrrsn .background(_:) is not .background(_:in:) – documentation is here https://developer.apple.com/documentation/swiftui/view/background(_:ignoressafeareaedges:)#:~:text=SwiftUI%20limits%20the%20background%20style%E2%80%99s%20extent%20to%20the%20modified%20view%E2%80%99s%20container%2Drelative%20shape.%20You%20can%20see%20this%20effect%20if%20you%20constrain%20the%20FlagLabel%20view%20with%20a%20containerShape(_:)%20modifier:
@dlx Not sure if I'm still missing it, but it's not clear to me from that page either that if I do `.background(.red, in: shape)` it will implicitly call `containerShape(shape)`
The way I'm reading it, it's saying that if I already have a containerShape set, then calling background will inherit that shape
@shnhrrsn oh sorry, you meant .containerShape(_:), I misunderstood – yeah, that doesn’t seem be documented, in fact, this is evidently wrong https://developer.apple.com/documentation/swiftui/view/background(_:in:fillstyle:)#:~:text=This%20modifier%20is%20a%20convenience%20method%20for%20placing%20a%20single%20shape%20behind%20a%20view.
I assume if go through the non-insettable code path things work as expected?
@dlx Yep, non-insettable is fine.
Had claude code dig into SwiftUICore and it was able to confirm what I was seeing at runtime:
https://gist.github.com/shnhrrsn/6fe5155a4d8de648079d494c76783c11
This really should be documented…
"So: whenever you use the InsettableShape overload of .background(_:in:fillStyle:), SwiftUI's graph setup for that modifier calls _ViewInputs.setContainerShape with your shape — which is the internal plumbing behind .containerShape(...). The non-insettable background(_:in:) with Shape does not do this[...]"
