Adds GeoDrawer.ProjectionMode helper, including .automatic mode

Sources/GeoDrawer/helpers/BoundingBox+Helpers.swift

@@ -0,0 +1,74 @@
+//
+//  BoundingBox+Helpers.swift
+//  GeoProjector
+//
+//  Created by Adrian Schönig on 18/9/2024.
+//
+
+import GeoJSONKit
+
+extension GeoJSON.BoundingBox {
+
+  public static func suggestedBox(for positions: [GeoJSON.Position], allowSpanningAntimeridian: Bool = true) -> GeoJSON.BoundingBox {
+    if positions.count == 1, let only = positions.first {
+      let extended1 = only.coordinate(at: 10_000, facing: 45)
+      let extended2 = only.coordinate(at: 10_000, facing: 225)
+      return GeoJSON.BoundingBox(positions: [extended1, extended2])
+
+    } else {
+      let smallestBoundingBox = GeoJSON.BoundingBox(positions: positions, allowSpanningAntimeridian: allowSpanningAntimeridian)
+      let fittedBoundingBox: GeoJSON.BoundingBox
+      if smallestBoundingBox.spansAntimeridian, smallestBoundingBox.longitudeSpan > 180 {
+        fittedBoundingBox = GeoJSON.BoundingBox(positions: positions, allowSpanningAntimeridian: false)
+      } else {
+        fittedBoundingBox = smallestBoundingBox
+      }
+      let paddedBoundingBox = fittedBoundingBox.scaled(x: 1.1, y: 1.1)
+      return paddedBoundingBox
+    }
+  }
+
+  public var latitudeSpan: Double {
+    northEasterlyLatitude - southWesterlyLatitude
+  }
+
+  public var longitudeSpan: Double {
+    if spansAntimeridian {
+      return northEasterlyLongitude + 360 - southWesterlyLongitude
+    } else {
+      return northEasterlyLongitude - southWesterlyLongitude
+    }
+  }
+
+  public var aspectRatio: Double {
+    if longitudeSpan > 0, latitudeSpan > 0 {
+      return longitudeSpan / latitudeSpan
+    } else {
+      return 0
+    }
+  }
+
+  public func scaled(x: Double, y: Double) -> GeoJSON.BoundingBox {
+    let latitudeDelta = (latitudeSpan * y - latitudeSpan) / 2
+    let longitudeDelta = (longitudeSpan * x - longitudeSpan) / 2
+    let candidate = GeoJSON.BoundingBox(
+      positions: [
+        .init(latitude: northEasterlyLatitude + latitudeDelta, longitude: northEasterlyLongitude + longitudeDelta),
+        .init(latitude: northEasterlyLatitude - latitudeDelta, longitude: northEasterlyLongitude - longitudeDelta),
+        .init(latitude: southWesterlyLatitude + latitudeDelta, longitude: southWesterlyLongitude + longitudeDelta),
+        .init(latitude: southWesterlyLatitude - latitudeDelta, longitude: southWesterlyLongitude - longitudeDelta),
+      ],
+      allowSpanningAntimeridian: spansAntimeridian // don't change that
+    )
+
+    // Scaling shouldn't allow going outside the valid latitude bounds. If it
+    // does, just abort and return un-scaled bounding box.
+    let validLatitudes = (-90.0)...(90.0)
+    if validLatitudes.contains(candidate.northEasterlyLatitude), validLatitudes.contains(candidate.southWesterlyLatitude) {
+      return candidate
+    } else {
+      return self
+    }
+  }
+
+}

Sources/GeoDrawer/styling/GeoDrawer+ProjectionMode.swift

@@ -0,0 +1,41 @@
+//
+//  GeoDrawer+ProjectionMode.swift
+//  GeoProjector
+//
+//  Created by Adrian Schönig on 18/9/2024.
+//
+
+import GeoJSONKit
+
+extension GeoDrawer {
+  public enum ProjectionMode: String {
+    case automatic
+
+    case mercator
+    case equirectangular
+    case equalEarth
+    case gallPeters
+    case azimuthal
+    case orthographic
+
+    public func resolve(for boundingBox: GeoJSON.BoundingBox) -> Projection {
+
+      switch self {
+      case .automatic where max(boundingBox.longitudeSpan, boundingBox.latitudeSpan) < 180, .orthographic:
+        return Projections.Orthographic(reference: boundingBox.center)
+      case .equalEarth, .automatic:
+        return Projections.EqualEarth(reference: boundingBox.center)
+
+      case .mercator:
+        return Projections.Mercator(reference: boundingBox.center)
+      case .equirectangular:
+        return Projections.Equirectangular(reference: boundingBox.center)
+      case .gallPeters:
+        return Projections.GallPeters(reference: boundingBox.center)
+      case .azimuthal:
+        return Projections.AzimuthalEquidistant(reference: boundingBox.center)
+      }
+
+    }
+  }
+}