Open Radar

 
Area:
MapKit

Summary:
After an MKAnnotationView has been created & displayed, then updating its image to one with a different horizontal size than the original image does not modify the x-position of the callout bubble. In other words, updating to a larger image in `mapView(_:didSelect:)` will present the callout at the correct y-position (at the top of the grown annotation view), but the x-position will fall short of the center. A workaround to this would be to modify the `calloutOffset` to the difference in distance between the old & new image centerX. This is obviously not preferred as a `calloutOffset` of `CGPoint.zero` should imply that the callout is horizontally centered above the annotation view.

Steps to Reproduce:
1. Set up an MKMapView with a list of annotations, each with a non-nil `title`
2. Within the delegate implementor, ensure that each `MKAnnotationView` has:
- `canShowCallout` set to `true`
- `image` set to a provided `UIImage`
3. Within `mapView(_:didSelect:)`, update the annotation view with a horizontally larger `UIImage` than the original
4. Within `mapView(_:didDeselect:)`, update the annotation view with the original image
5. Run the project and tap on any annotation view

Expected Results:
Callout bubble animates in (or not) to the correct position above the annotation view

Actual Results:
Callout bubble animates in to the correct y-position, but at the incorrect x-position of originalImage.width/2

Version/Build:
iOS 12.1.2, Xcode 10.1, Swift 4.2