Mirror Transitions

[davdroman]

This is an idea that came to mind while writing #6.

Oftentimes pop transitions will just be the mirror version of push transitions, but they currently need to be defined explicitly every time. Perhaps there's a way to skip the pop implementation altogether and use the mirrored version of push instead. Something like pop: .mirror.

Before:

extension NavigationTransition {
    static var swing: Self {
        let angle = Angle(degrees: 70)
        let offset: CGFloat = 150
        let scale: CGFloat = 0.5

        return .move(axis: .horizontal).combined(
            with: .asymmetric(
                push: .asymmetric(
                    insertion: [.rotate(-angle), .offset(x: offset), .opacity, .scale(scale)].combined(),
                    removal: [.rotate(angle), .offset(x: -offset)].combined()
                ),
                pop: .asymmetric(
                    insertion: [.rotate(angle), .offset(x: -offset), .opacity, .scale(scale), .bringToFront].combined(),
                    removal: [.rotate(-angle), .offset(x: offset)].combined()
                )
            )
        )
    }
}

After:

extension NavigationTransition {
    static var swing: Self {
        let angle = Angle(degrees: 70)
        let offset: CGFloat = 150
        let scale: CGFloat = 0.5

        return .move(axis: .horizontal).combined(
            with: .asymmetric(
                push: .asymmetric(
                    insertion: [.rotate(-angle), .offset(x: offset), .opacity, .scale(scale)].combined(),
                    removal: [.rotate(angle), .offset(x: -offset)].combined()
                ),
                pop: .mirror
            )
        )
    }
}

Implementation wise, I'm thinking this would require every transition instance to be mirrorable, which shouldn't be too hard to introduce as a requirement. However further thinking is needed on how exactly to do this without burdening developer experience too much.

[davdroman]

Thought over this further and it might require #6 to be done beforehand, since that'd probably turn AtomicTransition into a protocol to which each transition conforms, which would allow the introduction of a subprotocol (AtomicMirrorableTransition?) to opt into mirroring:

extension NavigationTransition {
    @Builder
    static var swing: Self {
        let angle = Angle(degrees: 70)
        let offset: CGFloat = 150

        Move(axis: .horizontal)
        Mirror {
            OnInsertion {
                Rotate(-angle)
                Offset(x: offset)
                Opacity()
                Scale(0.5)
            }
            OnRemoval {
                Rotate(angle)
                Offset(x: -offset)
            }
        }
    }
}

[davdroman]

Done! #24