Performance refactor

Example/ForeFlightKMLDemo.xcodeproj/project.pbxproj

@@ -7,8 +7,6 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
-		E9421CEB2E7A0A4200FD39E1 /* ForeFlightKML in Frameworks */ = {isa = PBXBuildFile; productRef = E9421CEA2E7A0A4200FD39E1 /* ForeFlightKML */; };
-		E94E2EDA2E9E8699006CBDB6 /* ForeFlightKML in Frameworks */ = {isa = PBXBuildFile; productRef = E94E2ED92E9E8699006CBDB6 /* ForeFlightKML */; };
 		E9D33C1E2EAFD4F70066F05A /* ForeFlightKML in Frameworks */ = {isa = PBXBuildFile; productRef = E9D33C1D2EAFD4F70066F05A /* ForeFlightKML */; };
 /* End PBXBuildFile section */
 
@@ -29,8 +27,6 @@
 			isa = PBXFrameworksBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
-				E9421CEB2E7A0A4200FD39E1 /* ForeFlightKML in Frameworks */,
-				E94E2EDA2E9E8699006CBDB6 /* ForeFlightKML in Frameworks */,
 				E9D33C1E2EAFD4F70066F05A /* ForeFlightKML in Frameworks */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
@@ -74,8 +70,6 @@
 			);
 			name = ForeFlightKMLDemo;
 			packageProductDependencies = (
-				E9421CEA2E7A0A4200FD39E1 /* ForeFlightKML */,
-				E94E2ED92E9E8699006CBDB6 /* ForeFlightKML */,
 				E9D33C1D2EAFD4F70066F05A /* ForeFlightKML */,
 			);
 			productName = ForeFlightKMLDemo;
@@ -107,7 +101,7 @@
 			mainGroup = E9421CAA2E7A09EA00FD39E1;
 			minimizedProjectReferenceProxies = 1;
 			packageReferences = (
-				E9D33C1C2EAFD4F70066F05A /* XCRemoteSwiftPackageReference "ForeFlightKML" */,
+				E9D33C1C2EAFD4F70066F05A /* XCLocalSwiftPackageReference ".." */,
 			);
 			preferredProjectObjectVersion = 77;
 			productRefGroup = E9421CB42E7A09EA00FD39E1 /* Products */;
@@ -360,29 +354,16 @@
 		};
 /* End XCConfigurationList section */
 
-/* Begin XCRemoteSwiftPackageReference section */
-		E9D33C1C2EAFD4F70066F05A /* XCRemoteSwiftPackageReference "ForeFlightKML" */ = {
-			isa = XCRemoteSwiftPackageReference;
-			repositoryURL = "https://github.com/Haelix-Code/ForeFlightKML/";
-			requirement = {
-				kind = upToNextMajorVersion;
-				minimumVersion = 0.2.1;
-			};
+/* Begin XCLocalSwiftPackageReference section */
+		E9D33C1C2EAFD4F70066F05A /* XCLocalSwiftPackageReference ".." */ = {
+			isa = XCLocalSwiftPackageReference;
+			relativePath = "..";
 		};
-/* End XCRemoteSwiftPackageReference section */
+/* End XCLocalSwiftPackageReference section */
 
 /* Begin XCSwiftPackageProductDependency section */
-		E9421CEA2E7A0A4200FD39E1 /* ForeFlightKML */ = {
-			isa = XCSwiftPackageProductDependency;
-			productName = ForeFlightKML;
-		};
-		E94E2ED92E9E8699006CBDB6 /* ForeFlightKML */ = {
-			isa = XCSwiftPackageProductDependency;
-			productName = ForeFlightKML;
-		};
 		E9D33C1D2EAFD4F70066F05A /* ForeFlightKML */ = {
 			isa = XCSwiftPackageProductDependency;
-			package = E9D33C1C2EAFD4F70066F05A /* XCRemoteSwiftPackageReference "ForeFlightKML" */;
 			productName = ForeFlightKML;
 		};
 /* End XCSwiftPackageProductDependency section */

Example/ForeFlightKMLDemo/KML/KMLGenerator.swift

@@ -4,7 +4,8 @@ import CoreLocation
 import ForeFlightKML
 
 enum KMLGenerator {
-    static func generateCircleKML(center: CLLocationCoordinate2D, radiusMeters: Double) throws -> BuildResult {
+    /// Builds a KML file and writes it to a temp directory, returning the URL.
+    static func generateCircleKML(center: CLLocationCoordinate2D, radiusMeters: Double) throws -> URL {
         let builder = ForeFlightKMLBuilder(documentName: "Foreflight KML Demo")
 
         let centerCoordinate = Coordinate(latitude: center.latitude, longitude: center.longitude)
@@ -23,8 +24,16 @@ enum KMLGenerator {
             radiusMeters: radiusMeters * 2,
             style: PolygonStyle(outlineColor: .black, fillColor: .warning.withAlpha(0.3)))
 
-        return try builder.build(as: .kmz)
+        let result = try builder.build(as: .kml)
 
+        let dateFormatter = DateFormatter()
+        dateFormatter.dateFormat = "yyyyMMdd'T'HHmmss'Z'"
+
+        let tmpURL = FileManager.default.temporaryDirectory
+            .appendingPathComponent("\(dateFormatter.string(from: Date())).\(result.fileExtension)")
+
+        try result.data.write(to: tmpURL, options: [.atomic])
+        return tmpURL
     }
 
     static func polygonCoordinatesForMap(center: CLLocationCoordinate2D, radiusMeters: Double) -> [CLLocationCoordinate2D] {

Example/ForeFlightKMLDemo/Views/ContentView.swift

@@ -1,11 +1,9 @@
 import SwiftUI
 import MapKit
-import ForeFlightKML
 
 struct ContentView: View {
     @State private var lastTapCoordinate: CLLocationCoordinate2D?
     @State private var kmlToShareURL: URL?
-    @State private var showingShare = false
 
     private let defaultRadiusMeters: Double = 500.0
 
@@ -26,49 +24,36 @@ struct ContentView: View {
                 Spacer()
                 HStack {
                     Spacer()
-                    Button(action: shareIfAvailable) {
+                    if let url = kmlToShareURL {
+                        ShareLink(item: url) {
+                            Image(systemName: "square.and.arrow.up")
+                                .font(.title2)
+                                .padding()
+                                .background(Color(.systemBackground).opacity(0.9))
+                                .clipShape(Circle())
+                        }
+                        .padding()
+                    } else {
                         Image(systemName: "square.and.arrow.up")
                             .font(.title2)
                             .padding()
                             .background(Color(.systemBackground).opacity(0.9))
                             .clipShape(Circle())
+                            .opacity(0.4)
+                            .padding()
                     }
-                    .disabled(kmlToShareURL == nil)
-                    .padding()
                 }
             }
         }
-        .sheet(isPresented: $showingShare) {
-            if let url = kmlToShareURL {
-                ActivityViewController(activityItems: [url])
-            } else {
-                Text("No KML available")
-            }
-        }
     }
 
     private func handleMapTap(_ coord: CLLocationCoordinate2D) {
         lastTapCoordinate = coord
         do {
-            let buildResult = try KMLGenerator.generateCircleKML(center: coord, radiusMeters: defaultRadiusMeters)
-
-            let dateFormatter = DateFormatter()
-            dateFormatter.dateFormat = "yyyyMMdd'T'HHmmss'Z'"
-
-            let tmpURL = FileManager.default.temporaryDirectory.appendingPathComponent("\(dateFormatter.string(from: Date())).\(buildResult.fileExtension)")
-
-            try buildResult.data.write(to: tmpURL)
-            kmlToShareURL = tmpURL
-            showingShare = true
+            kmlToShareURL = try KMLGenerator.generateCircleKML(center: coord, radiusMeters: defaultRadiusMeters)
         } catch {
-            print("Failed to write KMZ: \(error)")
+            print("Failed to generate KML: \(error)")
             kmlToShareURL = nil
         }
     }
-
-    private func shareIfAvailable() {
-        if kmlToShareURL != nil {
-            showingShare = true
-        }
-    }
 }

README.md

@@ -1,15 +1,16 @@
 # ForeFlightKML
 
-> Swift framework to build KML files in Jeppesen ForeFlight friendly format. 
+> Swift framework to build KML files in Jeppesen ForeFlight friendly format.
 
 This package provides a small, focused API for composing KML/KMZ documents suitable for importing into ForeFlight as **User Map Shapes (KML)**. It intentionally avoids UI concerns — it gives you `String` KML output (or bytes) which your app can write to disk and share using the standard iOS share sheet.
-    
+
 
 ## Quick highlights
 
 - Compose `Placemark`s with `Point`, `LineString`, `Polygon` and derived geometry helpers (circles, arc sectors, etc.).
 - Create reusable styles (`Style`, `LineStyle`, `PolyStyle`, `IconStyle`, `LabelStyle`) and assign them to placemarks.
-- `ForeFlightKMLBuilder` collects placemarks and styles, emits a complete `kml` or `kmz` document .
+- `ForeFlightKMLBuilder` collects placemarks and styles, emits a complete `kml` or `kmz` document.
+- Thread-safe — `ForeFlightKMLBuilder` is `Sendable`, so KML generation can run off the main thread.
 - Lightweight — no UI code.
 
 ## Install
@@ -18,8 +19,8 @@ This package provides a small, focused API for composing KML/KMZ documents suita
 3. Choose the `ForeFlightKML` package product and add it to your app target.
 
 
-## Example Output 
-Using the example given on the [ForeFlight website](https://foreflight.com/support/user-map-shapes/) the below is generated using this Framework. 
+## Example Output
+Using the example given on the [ForeFlight website](https://foreflight.com/support/user-map-shapes/) the below is generated using this Framework.
 
 See `/Tests/UserMapShapeTests/UserMapShapesSampleFullTest.swift`
 
@@ -29,27 +30,27 @@ See `/Tests/UserMapShapeTests/UserMapShapesSampleFullTest.swift`
 
 ```swift
 import ForeFlightKML
-import Geodesy (used for coordinates)
+import GeodesySpherical
 
 let builder = ForeFlightKMLBuilder(documentName: "Airport with ATZ")
 
 builder.addLine(
-    name: "Runway 15-33", 
-    coordinates: [Coordinate(latitude:, longitude:),Coordinate(latitude:, longitude:)],
-    style: LineStyle(color: .black)
+    name: "Runway 15-33",
+    coordinates: [Coordinate(latitude:, longitude:), Coordinate(latitude:, longitude:)],
+    style: PathStyle(color: .black)
 )
 
-builder.addLineCircle(
-    name: "Airport ATZ", 
-    center: Coordinate(latitude:, longitude:), 
+builder.addPolygonCircle(
+    name: "Airport ATZ",
+    center: Coordinate(latitude:, longitude:),
     radiusMeters: 4630,
-    PolygonStyle(outlineColor: .black, fillColor: .warning.withAlpha(0.3))
+    style: PolygonStyle(outlineColor: .black, fillColor: .warning.withAlpha(0.3))
 )
 
 let buildResult = try builder.build(as: .kmz)
 
-let url = FileManager.default.temporaryDirectory.appendingPathComponent("shapes\(buildResult.fileExtension)")
-try buildResult.data.write(to: tmpURL)
+let url = FileManager.default.temporaryDirectory.appendingPathComponent("shapes.\(buildResult.fileExtension)")
+try buildResult.data.write(to: url)
 presentShareSheet(with: url)
 ```
 
@@ -58,44 +59,71 @@ presentShareSheet(with: url)
 
 ## API Reference
 
-### KMLBuidler
- `ForeFlightKMLBuilder` is the builder for the KML/KMZ document. 
- - Document name can be set on `init` or with `setDocumentName()` 
+### KMLBuilder
+ `ForeFlightKMLBuilder` is the builder for the KML/KMZ document.
+ - Document name can be set on `init` or with `setDocumentName()`
+ - Coordinate precision can be configured with `setCoordinatePrecision(_:)` (default 8, see below)
  - Elements can be manually added using `addPlacemark(_:)`
  - The output is accessed by `try builder.build()`
 
+### Coordinate Precision
+
+By default coordinates are written with up to 8 decimal places, with trailing zeros trimmed for cleaner output:
+
+| Value | Output |
+|-------|--------|
+| `2.0` | `2.0` |
+| `51.750188` | `51.750188` |
+| `51.12345678` | `51.12345678` |
+
+You can customise the precision (1–15) via the builder:
+
+```swift
+let builder = ForeFlightKMLBuilder(documentName: "Low-res demo")
+    .setCoordinatePrecision(4) // max 4dp, trailing zeros trimmed
+```
+
+The `Coordinate.kmlString(precision:)` method also accepts a precision parameter for standalone use.
+
 ### KMLBuilder Convenience Elements
  - `addPoint` Add a point with style.
  - `addLine` Add a line connecting multiple coordinates.
  - `addLineCircle` Add a circular line (approximated by line segments).
  - `addLineSector` Add an arc sector line geometry.
  - `addPolygon` Add a polygon with outer boundary and optional holes.
- - `addPolygonCircle` Add a polygon with outer boundary and optional holes.
+ - `addPolygonCircle` Add a filled circular polygon.
  - `addPolygonSector` Add a filled sector polygon (pie slice).
  - `addPolygonAnnularSector` Add a filled annular (ring) sector polygon.
  - `addLabel` Add a text-only label placemark at a coordinate.
 
-### ForeflightKMLBuilder Export formats
-Type `BuildResult` contains: 
-``` 
+### ForeFlightKMLBuilder Export formats
+Type `BuildResult` contains:
+```
     data: Data
     fileExtension: String
     mimetype: String
 ```
-Specific data access: 
+Specific data access:
 - `kml Data` via `builder.build(as: .kml)`
 - `kmz Data` via `builder.build(as: .kmz)`
 - `kml String` via `builder.kmlString()` note: this can be unsafe and should only be used for debugging
-- KMZ (zipped KML) is required when using custom icons or using labelBadge (which uses a transparent .png under the hood). 
+- KMZ (zipped KML) is required when using custom icons or using labelBadge (which uses a transparent .png under the hood).
 
 ### Underlying elements
 - `Placemark` — a Feature containing a geometry (must implement `KMLElement`). Optionally attach a `KMLStyle`.
-- Geometry types: `Point`, `Line`, `LineCircle`, `LineSector` (sector of a Circle), `Polygon`, `PolygonCircle` (filled circle), `PolygonSector` (filled sector) `LinearRing`.
+- Geometry types: `Point`, `Line`, `LineCircle`, `LineSector` (sector of a Circle), `Polygon`, `PolygonCircle` (filled circle), `PolygonSector` (filled sector), `PolygonAnnularSector`, `LinearRing`.
 - `Style` and substyles: `LineStyle`, `PolyStyle`, `IconStyle`, `LabelStyle`.
 - `KMLColor` — helper to create the aabbggrr color values used by KML.
 
 Full public API surface is visible in the package sources.
 
+## Performance
+
+- **Buffer-based generation** — KML is built using a single mutable `String` buffer rather than array concatenation, avoiding intermediate allocations.
+- **Sendable** — `ForeFlightKMLBuilder` conforms to `Sendable`, allowing KML/KMZ generation to run on a background thread for a responsive UI.
+- **Smart compression** — small documents (< 100 KB) skip DEFLATE compression in KMZ output, reducing overhead.
+- **Efficient geometry** — circle point generation uses direct arithmetic rather than `Measurement` conversions.
+
 ## Notes, conventions and gotchas
 
 - **Coordinates order**: KML requires `longitude,latitude[,altitude]`. The public API accepts `Coordinate(latitude:..., longitude:...)` (from `Geodesy`) and the framework emits coordinates in the KML `lon,lat[,alt]` order.
@@ -106,7 +134,7 @@ Full public API surface is visible in the package sources.
 
 ## Demo & tests
 
-The repo contains an `Example` app that demonstrates building shapes and the `Tests` folder with unit and end to end example tests. 
+The repo contains an `Example` app that demonstrates building shapes and the `Tests` folder with unit and end to end example tests.
 
 ## Contributing
 

Sources/ForeFlightKML/CoreElements/LineString.swift

@@ -36,6 +36,16 @@ public protocol LineLike: KMLElement, AltitudeSupport {
 }
 
 extension LineLike {
+    public func write(to buffer: inout String) {
+        write(to: &buffer, precision: kDefaultCoordinatePrecision)
+    }
+
+    public func write(to buffer: inout String, precision: Int) {
+        let lineString = LineString(
+            coordinates: coordinates, altitude: altitude, tessellate: tessellate)
+        lineString.write(to: &buffer, precision: precision)
+    }
+
     public func kmlString() -> String {
         let lineString = LineString(
             coordinates: coordinates, altitude: altitude, tessellate: tessellate)