[ios] Adds pointForCoordinate/coordinateForPoint to MGLMapSnapshotOverlay (#15746)

* [ios] Adds `pointForCoordinate:`/`coordinateForPoint:` to MGLMapSnapshotOverlay

* [ios] Adds PR #

* [ios, macos] Update file lists & mac contexts

* [macos] Fix for image scale in overlay.

* [ios] Updated change log based on PR feedback.

7 files changed, 177 insertions, 12 deletions

diff --git a/platform/darwin/src/MGLMapSnapshotter.h b/platform/darwin/src/MGLMapSnapshotter.h
index 33febe0d0c..98c8e8a375 100644
--- a/platform/darwin/src/MGLMapSnapshotter.h
+++ b/platform/darwin/src/MGLMapSnapshotter.h
@@ -19,6 +19,31 @@ MGL_EXPORT
  */
 @property (nonatomic, readonly) CGContextRef context;
 
+#if TARGET_OS_IPHONE
+/**
+ Converts the specified map coordinate to a point in the coordinate space of the
+ context.
+ */
+- (CGPoint)pointForCoordinate:(CLLocationCoordinate2D)coordinate;
+
+/**
+ Converts the specified context point to a map coordinate.
+ */
+- (CLLocationCoordinate2D)coordinateForPoint:(CGPoint)point;
+
+#else
+/**
+ Converts the specified map coordinate to a point in the coordinate space of the
+ context.
+ */
+- (NSPoint)pointForCoordinate:(CLLocationCoordinate2D)coordinate;
+
+/**
+ Converts the specified context point to a map coordinate.
+ */
+- (CLLocationCoordinate2D)coordinateForPoint:(NSPoint)point;
+#endif
+
 @end
 
 /**
diff --git a/platform/darwin/src/MGLMapSnapshotter.mm b/platform/darwin/src/MGLMapSnapshotter.mm
index 85619a780b..0dde94292c 100644
--- a/platform/darwin/src/MGLMapSnapshotter.mm
+++ b/platform/darwin/src/MGLMapSnapshotter.mm
@@ -17,6 +17,8 @@
 #import "MGLAttributionInfo_Private.h"
 #import "MGLLoggingConfiguration_Private.h"
 #import "MGLRendererConfiguration.h"
+#import "MGLMapSnapshotter_Private.h"
+
 #if TARGET_OS_IPHONE || TARGET_OS_SIMULATOR
 #import "MGLMapboxEvents.h"
 #endif
@@ -33,23 +35,61 @@ const CGPoint MGLLogoImagePosition = CGPointMake(8, 8);
 const CGFloat MGLSnapshotterMinimumPixelSize = 64;
 
 
-@interface MGLMapSnapshotOverlay()
-
-- (instancetype)initWithContext:(CGContextRef)context;
+@interface MGLMapSnapshotOverlay() <MGLMapSnapshotProtocol>
+@property (nonatomic, assign) CGFloat scale;
+- (instancetype)initWithContext:(CGContextRef)context scale:(CGFloat)scale pointForFn:(mbgl::MapSnapshotter::PointForFn)pointForFn latLngForFn:(mbgl::MapSnapshotter::LatLngForFn)latLngForFn;
 
 @end
 
-@implementation MGLMapSnapshotOverlay
+@implementation MGLMapSnapshotOverlay {
+    mbgl::MapSnapshotter::PointForFn _pointForFn;
+    mbgl::MapSnapshotter::LatLngForFn _latLngForFn;
+}
 
-- (instancetype) initWithContext:(CGContextRef)context {
+- (instancetype) initWithContext:(CGContextRef)context scale:(CGFloat)scale pointForFn:(mbgl::MapSnapshotter::PointForFn)pointForFn latLngForFn:(mbgl::MapSnapshotter::LatLngForFn)latLngForFn {
     self = [super init];
     if (self) {
         _context = context;
+        _scale = scale;
+        _pointForFn = pointForFn;
+        _latLngForFn = latLngForFn;
     }
 
     return self;
 }
 
+#if TARGET_OS_IPHONE
+
+- (CGPoint)pointForCoordinate:(CLLocationCoordinate2D)coordinate
+{
+    mbgl::ScreenCoordinate sc = _pointForFn(MGLLatLngFromLocationCoordinate2D(coordinate));
+    return CGPointMake(sc.x, sc.y);
+}
+
+- (CLLocationCoordinate2D)coordinateForPoint:(CGPoint)point
+{
+    mbgl::LatLng latLng = _latLngForFn(mbgl::ScreenCoordinate(point.x, point.y));
+    return MGLLocationCoordinate2DFromLatLng(latLng);
+}
+
+#else
+
+- (NSPoint)pointForCoordinate:(CLLocationCoordinate2D)coordinate
+{
+    mbgl::ScreenCoordinate sc = _pointForFn(MGLLatLngFromLocationCoordinate2D(coordinate));
+    CGFloat height = ((CGFloat)CGBitmapContextGetHeight(self.context))/self.scale;
+    return NSMakePoint(sc.x, height - sc.y);
+}
+
+- (CLLocationCoordinate2D)coordinateForPoint:(NSPoint)point
+{
+    CGFloat height = ((CGFloat)CGBitmapContextGetHeight(self.context))/self.scale;
+    auto screenCoord = mbgl::ScreenCoordinate(point.x, height - point.y);
+    mbgl::LatLng latLng = _latLngForFn(screenCoord);
+    return MGLLocationCoordinate2DFromLatLng(latLng);
+}
+
+#endif
 @end
 
 @implementation MGLMapSnapshotOptions
@@ -78,7 +118,7 @@ const CGFloat MGLSnapshotterMinimumPixelSize = 64;
 
 @end
 
-@interface MGLMapSnapshot()
+@interface MGLMapSnapshot() <MGLMapSnapshotProtocol>
 - (instancetype)initWithImage:(nullable MGLImage *)image scale:(CGFloat)scale pointForFn:(mbgl::MapSnapshotter::PointForFn)pointForFn latLngForFn:(mbgl::MapSnapshotter::LatLngForFn)latLngForFn;
 
 @property (nonatomic) CGFloat scale;
@@ -93,8 +133,8 @@ const CGFloat MGLSnapshotterMinimumPixelSize = 64;
 {
     self = [super init];
     if (self) {
-        _pointForFn = std::move(pointForFn);
-        _latLngForFn = std::move(latLngForFn);
+        _pointForFn = pointForFn;
+        _latLngForFn = latLngForFn;
         _scale = scale;
         _image = image;
     }
@@ -328,7 +368,10 @@ const CGFloat MGLSnapshotterMinimumPixelSize = 64;
     CGContextRef currentContext = UIGraphicsGetCurrentContext();
 
     if (currentContext && overlayHandler) {
-        MGLMapSnapshotOverlay *snapshotOverlay = [[MGLMapSnapshotOverlay alloc] initWithContext:currentContext];
+        MGLMapSnapshotOverlay *snapshotOverlay = [[MGLMapSnapshotOverlay alloc] initWithContext:currentContext
+                                                                                          scale:scale
+                                                                                     pointForFn:pointForFn
+                                                                                    latLngForFn:latLngForFn];
         CGContextSaveGState(snapshotOverlay.context);
         overlayHandler(snapshotOverlay);
         CGContextRestoreGState(snapshotOverlay.context);
@@ -409,7 +452,10 @@ const CGFloat MGLSnapshotterMinimumPixelSize = 64;
     
     NSGraphicsContext *currentContext = [NSGraphicsContext currentContext];
     if (currentContext && overlayHandler) {
-        MGLMapSnapshotOverlay *snapshotOverlay = [[MGLMapSnapshotOverlay alloc] initWithContext:currentContext.CGContext];
+        MGLMapSnapshotOverlay *snapshotOverlay = [[MGLMapSnapshotOverlay alloc] initWithContext:currentContext.CGContext
+                                                                                          scale:scale
+                                                                                     pointForFn:pointForFn
+                                                                                    latLngForFn:latLngForFn];
         [currentContext saveGraphicsState];
         overlayHandler(snapshotOverlay);
         [currentContext restoreGraphicsState];
diff --git a/platform/darwin/src/MGLMapSnapshotter_Private.h b/platform/darwin/src/MGLMapSnapshotter_Private.h
new file mode 100644
index 0000000000..205e51a6de
--- /dev/null
+++ b/platform/darwin/src/MGLMapSnapshotter_Private.h
@@ -0,0 +1,14 @@
+#import "MGLMapSnapshotter.h"
+
+@protocol MGLMapSnapshotProtocol <NSObject>
+
+#if TARGET_OS_IPHONE
+- (CGPoint)pointForCoordinate:(CLLocationCoordinate2D)coordinate;
+- (CLLocationCoordinate2D)coordinateForPoint:(CGPoint)point;
+
+#else
+- (NSPoint)pointForCoordinate:(CLLocationCoordinate2D)coordinate;
+- (CLLocationCoordinate2D)coordinateForPoint:(NSPoint)point;
+#endif
+
+@end
diff --git a/platform/ios/CHANGELOG.md b/platform/ios/CHANGELOG.md
index d636d94811..d11c9a5f95 100644
--- a/platform/ios/CHANGELOG.md
+++ b/platform/ios/CHANGELOG.md
@@ -12,6 +12,7 @@ Mapbox welcomes participation and contributions from everyone. Please read [CONT
 
 ### Other changes
 
+* Added `-[MGLMapSnapshotOverlay coordinateForPoint:]` and `-[MGLMapSnapshotOverlay pointForCoordinate:]` to convert between context and map coordinates, mirroring those of `MGLMapSnapshot`. ([#15746](https://github.com/mapbox/mapbox-gl-native/pull/15746))
 * Suppress network requests for expired tiles update, if these tiles are invisible. ([#15741](https://github.com/mapbox/mapbox-gl-native/pull/15741))
 * Fixed an issue that caused `MGLScaleBar` to have an incorrect size when resizing or rotating. ([#15703](https://github.com/mapbox/mapbox-gl-native/pull/15703))
 
diff --git a/platform/ios/Integration Tests/Snapshotter Tests/MGLMapSnapshotterTest.m b/platform/ios/Integration Tests/Snapshotter Tests/MGLMapSnapshotterTest.m
index 19718165b3..9ef2054dff 100644
--- a/platform/ios/Integration Tests/Snapshotter Tests/MGLMapSnapshotterTest.m
+++ b/platform/ios/Integration Tests/Snapshotter Tests/MGLMapSnapshotterTest.m
@@ -1,4 +1,5 @@
 #import "MGLMapViewIntegrationTest.h"
+#import "MGLMapSnapshotter_Private.h"
 
 @interface MGLMapSnapshotter ()
 @property (nonatomic) BOOL cancelled;
@@ -24,6 +25,21 @@ MGLMapSnapshotter* snapshotterWithCoordinates(CLLocationCoordinate2D coordinates
     return snapshotter;
 }
 
+MGLMapSnapshotter* snapshotterWithBounds(MGLCoordinateBounds bounds, CGSize size) {
+
+    MGLMapCamera* mapCamera = [[MGLMapCamera alloc] init];
+    MGLMapSnapshotOptions* options = [[MGLMapSnapshotOptions alloc] initWithStyleURL:[MGLStyle satelliteStreetsStyleURL]
+                                                                              camera:mapCamera
+                                                                                size:size];
+    options.coordinateBounds = bounds;
+
+    // Create and start the snapshotter
+    MGLMapSnapshotter* snapshotter = [[MGLMapSnapshotter alloc] initWithOptions:options];
+    return snapshotter;
+}
+
+
+
 @implementation MGLMapSnapshotterTest
 
 - (void)testMultipleSnapshotsWithASingleSnapshotter🔒 {
@@ -462,4 +478,60 @@ MGLMapSnapshotter* snapshotterWithCoordinates(CLLocationCoordinate2D coordinates
     [self waitForExpectations:@[expectation] timeout:10.0];
 }
 
+- (void)testSnapshotCoordinatesWithOverlayHandler🔒 {
+    CGSize size = self.mapView.bounds.size;
+
+    XCTestExpectation *expectation = [self expectationWithDescription:@"snapshot with overlay succeeds"];
+    expectation.expectedFulfillmentCount = 2;
+
+    CLLocationCoordinate2D london = { .latitude = 51.5074, .longitude = -0.1278 };
+    CLLocationCoordinate2D paris  = { .latitude = 48.8566, .longitude = 2.3522 };
+
+    MGLCoordinateBounds bounds = {
+        .ne = london,
+        .sw = paris
+    };
+
+    MGLMapSnapshotter *snapshotter = snapshotterWithBounds(bounds, size);
+    XCTAssertNotNil(snapshotter);
+
+    void (^testCoordinates)(id<MGLMapSnapshotProtocol>) = ^(id<MGLMapSnapshotProtocol> snapshot){
+        XCTAssertNotNil(snapshot);
+
+        CGPoint londonPoint = [snapshot pointForCoordinate:london];
+        CGPoint parisPoint  = [snapshot pointForCoordinate:paris];
+
+        XCTAssertEqualWithAccuracy(londonPoint.x, 0, 0.1);
+        XCTAssertEqualWithAccuracy(parisPoint.x, size.width, 0.1);
+
+        // Vertically, London and Paris are inset (due to the size vs coordinate bounds)
+        XCTAssert(parisPoint.y > londonPoint.y);
+        XCTAssert(londonPoint.y > 0.0);
+        XCTAssert(parisPoint.y < size.height);
+
+        CLLocationCoordinate2D london2 = [snapshot coordinateForPoint:londonPoint];
+        CLLocationCoordinate2D paris2  = [snapshot coordinateForPoint:parisPoint];
+
+        XCTAssertEqualWithAccuracy(london.latitude,  london2.latitude,  0.0000001);
+        XCTAssertEqualWithAccuracy(london.longitude, london2.longitude, 0.0000001);
+        XCTAssertEqualWithAccuracy(paris.latitude,   paris2.latitude,   0.0000001);
+        XCTAssertEqualWithAccuracy(paris.longitude,  paris2.longitude,  0.0000001);
+    };
+
+    [snapshotter startWithOverlayHandler:^(MGLMapSnapshotOverlay *snapshotOverlay) {
+        XCTAssert([snapshotOverlay conformsToProtocol:@protocol(MGLMapSnapshotProtocol)]);
+        testCoordinates((id<MGLMapSnapshotProtocol>)snapshotOverlay);
+
+        [expectation fulfill];
+    } completionHandler:^(MGLMapSnapshot * _Nullable snapshot, NSError * _Nullable error) {
+        XCTAssert([snapshot conformsToProtocol:@protocol(MGLMapSnapshotProtocol)]);
+        testCoordinates((id<MGLMapSnapshotProtocol>)snapshot);
+
+        [expectation fulfill];
+    }];
+
+    [self waitForExpectations:@[expectation] timeout:10.0];
+}
+
+
 @end
diff --git a/platform/ios/ios.xcodeproj/project.pbxproj b/platform/ios/ios.xcodeproj/project.pbxproj
index 20001c26a8..c873847b4f 100644
--- a/platform/ios/ios.xcodeproj/project.pbxproj
+++ b/platform/ios/ios.xcodeproj/project.pbxproj
@@ -528,6 +528,8 @@
 		CABE5DAD2072FAB40003AF3C /* Mapbox.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = DA8847D21CBAF91600AB86E3 /* Mapbox.framework */; };
 		CAD9D0AA22A86D6F001B25EE /* MGLResourceTests.mm in Sources */ = {isa = PBXBuildFile; fileRef = CAD9D0A922A86D6F001B25EE /* MGLResourceTests.mm */; };
 		CAE7AD5520F46EF5003B6782 /* MGLMapSnapshotterSwiftTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = CAE7AD5420F46EF5003B6782 /* MGLMapSnapshotterSwiftTests.swift */; };
+		CAFB3C14234505D500399265 /* MGLMapSnapshotter_Private.h in Headers */ = {isa = PBXBuildFile; fileRef = CAFB3C13234505D500399265 /* MGLMapSnapshotter_Private.h */; };
+		CAFB3C15234505D500399265 /* MGLMapSnapshotter_Private.h in Headers */ = {isa = PBXBuildFile; fileRef = CAFB3C13234505D500399265 /* MGLMapSnapshotter_Private.h */; };
 		CF75A91522D85E860058A5C4 /* MGLLoggingConfiguration.mm in Sources */ = {isa = PBXBuildFile; fileRef = CF75A91422D85E860058A5C4 /* MGLLoggingConfiguration.mm */; };
 		CF75A91622D85E860058A5C4 /* MGLLoggingConfiguration.mm in Sources */ = {isa = PBXBuildFile; fileRef = CF75A91422D85E860058A5C4 /* MGLLoggingConfiguration.mm */; };
 		DA00FC8E1D5EEB0D009AABC8 /* MGLAttributionInfo.h in Headers */ = {isa = PBXBuildFile; fileRef = DA00FC8C1D5EEB0D009AABC8 /* MGLAttributionInfo.h */; settings = {ATTRIBUTES = (Public, ); }; };
@@ -1072,8 +1074,8 @@
 		5580B45A229570A10091291B /* MGLMapView+OpenGL.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = "MGLMapView+OpenGL.mm"; sourceTree = "<group>"; };
 		558DE79E1E5615E400C7916D /* MGLFoundation_Private.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = MGLFoundation_Private.h; sourceTree = "<group>"; };
 		558DE79F1E5615E400C7916D /* MGLFoundation.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = MGLFoundation.mm; sourceTree = "<group>"; };
-		55CF752E213ED92000ED86C4 /* libmbgl-vendor-icu.a */ = {isa = PBXFileReference; explicitFileType = archive.ar; path = libmbgl-vendor-icu.a; sourceTree = BUILT_PRODUCTS_DIR; };
-		55CF7530213ED92A00ED86C4 /* libmbgl-vendor-icu.a */ = {isa = PBXFileReference; explicitFileType = archive.ar; path = libmbgl-vendor-icu.a; sourceTree = BUILT_PRODUCTS_DIR; };
+		55CF752E213ED92000ED86C4 /* libmbgl-vendor-icu.a */ = {isa = PBXFileReference; explicitFileType = archive.ar; path = "libmbgl-vendor-icu.a"; sourceTree = BUILT_PRODUCTS_DIR; };
+		55CF7530213ED92A00ED86C4 /* libmbgl-vendor-icu.a */ = {isa = PBXFileReference; explicitFileType = archive.ar; path = "libmbgl-vendor-icu.a"; sourceTree = BUILT_PRODUCTS_DIR; };
 		55D120A71F791007004B6D81 /* libmbgl-loop-darwin.a */ = {isa = PBXFileReference; explicitFileType = archive.ar; path = "libmbgl-loop-darwin.a"; sourceTree = BUILT_PRODUCTS_DIR; };
 		55D120A91F79100C004B6D81 /* libmbgl-filesource.a */ = {isa = PBXFileReference; explicitFileType = archive.ar; path = "libmbgl-filesource.a"; sourceTree = BUILT_PRODUCTS_DIR; };
 		55D8C9941D0F133500F42F10 /* config.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; name = config.xcconfig; path = ../../build/ios/config.xcconfig; sourceTree = "<group>"; };
@@ -1218,6 +1220,7 @@
 		CAD9D0A922A86D6F001B25EE /* MGLResourceTests.mm */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.objcpp; name = MGLResourceTests.mm; path = ../../darwin/test/MGLResourceTests.mm; sourceTree = "<group>"; };
 		CAE7AD5320F46EF5003B6782 /* integration-Bridging-Header.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = "integration-Bridging-Header.h"; sourceTree = "<group>"; };
 		CAE7AD5420F46EF5003B6782 /* MGLMapSnapshotterSwiftTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MGLMapSnapshotterSwiftTests.swift; sourceTree = "<group>"; };
+		CAFB3C13234505D500399265 /* MGLMapSnapshotter_Private.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = MGLMapSnapshotter_Private.h; sourceTree = "<group>"; };
 		CF75A91422D85E860058A5C4 /* MGLLoggingConfiguration.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = MGLLoggingConfiguration.mm; sourceTree = "<group>"; };
 		DA00FC8C1D5EEB0D009AABC8 /* MGLAttributionInfo.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = MGLAttributionInfo.h; sourceTree = "<group>"; };
 		DA00FC8D1D5EEB0D009AABC8 /* MGLAttributionInfo.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = MGLAttributionInfo.mm; sourceTree = "<group>"; };
@@ -2151,6 +2154,7 @@
 				DA8847E21CBAFA5100AB86E3 /* MGLMapCamera.h */,
 				DA8848031CBAFA6200AB86E3 /* MGLMapCamera.mm */,
 				927FBCFD1F4DB05500F8BF1F /* MGLMapSnapshotter.h */,
+				CAFB3C13234505D500399265 /* MGLMapSnapshotter_Private.h */,
 				927FBCFE1F4DB05500F8BF1F /* MGLMapSnapshotter.mm */,
 				DD0902A41DB18F1B00C5BDCE /* MGLNetworkConfiguration.h */,
 				1F2B94BF221636D800210640 /* MGLNetworkConfiguration_Private.h */,
@@ -2529,6 +2533,7 @@
 				1F6A82A221360F9D00BA5B41 /* MGLLoggingConfiguration.h in Headers */,
 				DA8848311CBAFA6200AB86E3 /* NSString+MGLAdditions.h in Headers */,
 				967C864B210A9D3C004DF794 /* UIDevice+MGLAdditions.h in Headers */,
+				CAFB3C14234505D500399265 /* MGLMapSnapshotter_Private.h in Headers */,
 				1FCAE2A220B872A400C577DD /* MGLLocationManager.h in Headers */,
 				DACA86262019218600E9693A /* MGLRasterDEMSource.h in Headers */,
 				353933F81D3FB79F003F57D7 /* MGLLineStyleLayer.h in Headers */,
@@ -2722,6 +2727,7 @@
 				35E1A4D91D74336F007AA97F /* MGLValueEvaluator.h in Headers */,
 				DABFB8701CBE9A0F00D62B32 /* MGLMapView+IBAdditions.h in Headers */,
 				9C6E283822A982670056B7BE /* MMEEventLogger.h in Headers */,
+				CAFB3C15234505D500399265 /* MGLMapSnapshotter_Private.h in Headers */,
 				6F018BAF220031BF003E7269 /* UIView+MGLAdditions.h in Headers */,
 				96E516EA2000560B00A02306 /* MGLAnnotationView_Private.h in Headers */,
 				96E516FB20005A4000A02306 /* MGLUserLocationHeadingBeamLayer.h in Headers */,
diff --git a/platform/ios/sdk-files.json b/platform/ios/sdk-files.json
index 0df4b381ba..dc59e179c8 100644
--- a/platform/ios/sdk-files.json
+++ b/platform/ios/sdk-files.json
@@ -243,6 +243,7 @@
         "MMEDate.h": "platform/ios/vendor/mapbox-events-ios/MapboxMobileEvents/MMEDate.h",
         "NSString+MGLAdditions.h": "platform/darwin/src/NSString+MGLAdditions.h",
         "UIDevice+MGLAdditions.h": "platform/ios/src/UIDevice+MGLAdditions.h",
+        "MGLMapSnapshotter_Private.h": "platform/darwin/src/MGLMapSnapshotter_Private.h",
         "MGLRendererFrontend.h": "platform/darwin/src/MGLRendererFrontend.h",
         "MGLStyleValue_Private.h": "platform/darwin/src/MGLStyleValue_Private.h",
         "MGLFillExtrusionStyleLayer_Private.h": "platform/darwin/src/MGLFillExtrusionStyleLayer_Private.h",