[WIP] Expose map camera and allow direct transformations of modified annotations and annotation views

[alex-reilly-pronto]

Hi! Thanks for maintaining this library. It's been a pleasure to use. I've got some annotations where I want to maintain their orientation relative to the map and move them over time, so I'm exposing the camera along with a closure that gives the user direct access to modified annotations and annotation views.

The suggested method online for changing annotation location is to use a MKPointAnnotation rather than an MKAnnotation, and to alter the coordinate field and for changing annotation orientation is to do a CGAffineTransform on the view itself. I'm doing both, but I'm open to something else if you've got a suggestion. It does feel like this requires developers to touch UIKit more than you'd probably like.

Here's a snippet of it in action.

// ...
.modifiedAnnotations { modifiedAnnotation, mkannotation, view in
  mkannotation.coordinate = modification.coordinate
  view.transform = CGAffineTransform(
    rotationAngle: modifiedAnnotation.annotationHeading.degreesToRadians
  )
}
.camera(viewStore.binding(get: \.camera, send: MapAction.moveCamera))

Here we've got the camera bound to a field in my view's state, which is being used to calculate annotationHeading behind the scenes.

Prior to this, if an annotation was modified it wouldn't be updated because Map.Coordinator was only checking for inserted or removed ids. Because of that, annotations are now required to be Equatable so that the coordinator can check for modified annotations in addition to inserted and removed annotations.

If we naively remove and then insert modified annotations, then that causes the annotation to flicker.

Breaking Changes

• annotation items are now required to be Equatable

[pauljohanneskraft]

Hey @alex-reilly-pronto ! Thank you for your contribution!

Unfortunately, there are still some things to improve on, so here is a first feedback from my side:

• You can already use a custom MKAnnotation type - no need to force everyone to use it. MKPointAnnotation conforms to MKAnnotation, so you can simply use these initializers with your annotations and you are good to go. Please also do not remove the existing annotation types.
• MKMapView lazily loads annotation views by design, not by accident. The views should be created whenever MKMapView requests it and not whenever an annotation is added to the view, since it might not be visible to the user and therefore has no reason to exist.
• I would only use Binding, if it would actually be a two-way binding. If not, we can use a closure that gets called, whenever the camera changes or something like that. I would also propose to propagate this with the use of the environment rather than setting individual properties on the struct.
• I'm not yet sure about making annotations Equatable, since that could pose other issues. Especially in the case of making the backwards support Equatable just by Identifiable could create unforeseen issues. I need to think about it a bit more though, so not a clear decision yet.

Thank you once again for your contribution. Please let me know, what you think about this and whether you want to continue working on this pull request 😊

[alex-reilly-pronto]

It might make sense to back up and reassess what it is I want here. I think the ideal setup would let me do something like

func truckAnnotation(annotation: TruckAnnotationModel) -> MapAnnotation {
  return ViewMapAnnotation(coordinate: annotation.location.coordinate) {
    ZStack {
      Circle()
        .foregroundColor(.indigo)

      Image(systemName: "location.north.fill")
        .foregroundColor(.white)
        .frame(width: 20, height: 20)
    }
    .frame(width: 35, height: 35)
    .background(Color.red)
    .rotation(Angle(degrees: annotation.annotationHeading) // <- important part
  }
}

But this doesn't work because the view is created exactly once when it first shows up on screen. Maybe that restriction is unnecessary and can be worked around.

[alex-reilly-pronto]

Closing this out for now.