feat: experimental Kotlin Multiplatform support (maps-compose-multiplatform)

[kikoso]

Experimental Kotlin Multiplatform support: maps-compose-multiplatform shows a Google Map from shared Compose code on Android (through maps-compose) and iOS (through the Google Maps SDK for iOS), with an API that follows maps-compose.

GoogleMap(cameraPositionState = rememberCameraPositionState { position = cameraPosition(sydney, 12f) }) {
    Marker(state = rememberMarkerState(sydney), title = "Sydney")
    Circle(center = sydney, radius = 1_000.0)
    Clustering(items = places)
}

API

• GoogleMap with CameraPositionState (two-way: moves from code, follows gestures, animate()), MapProperties, MapUiSettings, map clicks, long clicks and onMapLoaded.
• Marker (draggable, tappable, tinted pin), Polyline, Polygon with holes, Circle. Each call keeps one native object that is updated in place, so nothing is cleared and recreated on recomposition.
• Clustering reclusters as the camera zooms, once per zoom level, and zooms in on a cluster tap.
• LatLng, CameraPosition and the clustering algorithms come from the multiplatform modules of android-maps-utils (feat: experimental Kotlin Multiplatform support (clustering, library, heatmaps) android-maps-utils#1774), currently 6.1.0-SNAPSHOT.
• Not yet: custom marker icons, ground and tile overlays, Street View, MapEffect. The README lists them.

Demos

maps-compose-multiplatform-demo holds six demos (camera, markers, shapes, clustering, map settings, map clicks). The "Multiplatform demos" entry of maps-app and the iOS app show the same screens; the iOS app no longer has its own Swift list. -demo <index> (iOS) or --ei demo <index> (Android) opens one directly.

Build, publishing and CI

• KmpPublishingConventionPlugin: explicit API, iOS arm64 and simulator arm64 targets, lint, Kover, Maven Central publishing as maps-compose-multiplatform.
• Public API checks for the iOS klibs (Kotlin ABI validation) and the Android target (binary-compatibility-validator), committed under api/.
• Publishing a release fails while mapsutilsKmp is a snapshot.
• New Multiplatform (iOS) workflow on macOS: iOS simulator tests, API check, frameworks and the iOS app. The publish workflow moves to macOS, which the iOS klibs need.
• Compose Multiplatform 1.7.3 to 1.12.1 (1.7.3 klibs no longer link with Kotlin 2.4). No iosX64: Compose Multiplatform dropped it.
• The Xcode project is generated by create_project.rb and no longer checked in.

Tests

19 common tests (camera state, content registration and updates, clustering on zoom) run on the JVM and the iOS simulator. Locally: full CI build, the maps-app smoke and menu tests for the multiplatform entry on an API 36 emulator, and all six demos checked on both an Android emulator and an iOS simulator.

Before this can merge

android-maps-utils 6.1.0 has to ship with the KMP modules, and mapsutilsKmp move to it.

BEGIN_COMMIT_OVERRIDE
feat: experimental maps-compose-multiplatform library for Android and iOS
feat: shared camera state, map content and clustering in maps-compose-multiplatform
build: publish maps-compose-multiplatform with API checks, lint and iOS CI
END_COMMIT_OVERRIDE

[googlemaps-bot]

Code Coverage

Overall Project	44.37% -0.1%	🍏
Files changed	0%	❌

Module	Coverage
debug	24.61% -0.2%	❌

Files

Module	File	Coverage
debug	KmpMapActivity.kt	0%	❌
	Demo.kt	0% -0.86%	❌

[github-actions]

Coverage (unit tests)

Compared against 597c8db on main (#1023).

Module	Line %	Change	Branch %	Change
maps-compose	0.00%	no change	0.00%	no change
maps-compose-multiplatform	61.63%	new	26.40%	new
maps-compose-utils	2.04%	no change	0.49%	no change
maps-compose-widgets	0.00%	no change	0.00%	no change
TOTAL	8.54%	🔺 +8.12	3.17%	🔺 +3.08

_{Line and branch coverage from unit test reports. History is recorded on the coverage-history branch after each merge to main.}