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Add MGLCircle (with radius expressed in physical units) #14534
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| #import <Foundation/Foundation.h> | ||
| #import <CoreLocation/CoreLocation.h> | ||
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| #import "MGLShape.h" | ||
| #import "MGLGeometry.h" | ||
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| #import "MGLTypes.h" | ||
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| NS_ASSUME_NONNULL_BEGIN | ||
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| /** | ||
| An `MGLCircle` object represents a closed, circular shape also known as a | ||
| <a href="https://en.wikipedia.org/wiki/Spherical_cap">spherical cap</a>. A | ||
| circle is defined by a center coordinate, specified as a | ||
| `CLLocationCoordinate2D` instance, and a physical radius measured in meters. | ||
| The circle is approximated as a polygon with a large number of vertices and | ||
| edges. Due to the map’s Spherical Mercator projection, a large enough circle | ||
| appears as an elliptical or even sinusoidal shape. You could use a circle to | ||
| visualize for instance an impact zone, the `CLLocation.horizontalAccuracy` of a | ||
| GPS location update, the regulated airspace around an airport, or the | ||
| addressable consumer market around a city. | ||
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| You can add a circle overlay directly to a map view using the | ||
| `-[MGLMapView addAnnotation:]` or `-[MGLMapView addOverlay:]` method. Configure | ||
| a circle overlay’s appearance using | ||
| `-[MGLMapViewDelegate mapView:strokeColorForShapeAnnotation:]` and | ||
| `-[MGLMapViewDelegate mapView:fillColorForShape:]`. | ||
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| Alternatively, you can add a circle to the map by adding it to an | ||
| `MGLShapeSource` object. Because GeoJSON cannot represent a curve per se, the | ||
| circle is automatically converted to a polygon. See the `MGLPolygon` class for | ||
| more information about polygons. | ||
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| Do not confuse this class with `MGLCircleStyleLayer`, which renders a circle | ||
| defined by a center coordinate and a fixed _screen_ radius measured in points | ||
| regardless of the map’s zoom level. | ||
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| The polygon that approximates an `MGLCircle` has a large number of vertices. | ||
| If you do not need the circle to appear smooth at every possible zoom level, | ||
| use a many-sided regular `MGLPolygon` instead for better performance. | ||
| */ | ||
| MGL_EXPORT | ||
| @interface MGLCircle : MGLShape | ||
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| /** | ||
| The coordinate around which the circle is centered. | ||
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| Each coordinate along the circle’s edge is equidistant from this coordinate. | ||
| The center coordinate’s latitude helps determine the minimum spacing between | ||
| each vertex along the edge of the polygon that approximates the circle. | ||
| */ | ||
| @property (nonatomic) CLLocationCoordinate2D coordinate; | ||
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| /** | ||
| The radius of the circular area, measured in meters across the Earth’s surface. | ||
| */ | ||
| @property (nonatomic) CLLocationDistance radius; | ||
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| /** | ||
| Creates and returns an `MGLCircle` object centered around the given coordinate | ||
| and extending in all directions by the given physical distance. | ||
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| @param centerCoordinate The coordinate around which the circle is centered. | ||
| @param radius The radius of the circular area, measured in meters across the | ||
| Earth’s surface. | ||
| @return A new circle object. | ||
| */ | ||
| + (instancetype)circleWithCenterCoordinate:(CLLocationCoordinate2D)centerCoordinate radius:(CLLocationDistance)radius; | ||
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| /** | ||
| Creates and returns an `MGLCircle` object that fills the given coordinate | ||
| bounds. | ||
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| @param coordinateBounds The coordinate bounds to fill. The circle is centered | ||
| around the center of the coordinate bounds. The circle’s edge touches at | ||
| least two of the sides of the coordinate bounds. If the coordinate bounds | ||
| does not represent a square area, the circle extends beyond two of its | ||
| sides. | ||
| @return A new circle object. | ||
| */ | ||
| + (instancetype)circleWithCoordinateBounds:(MGLCoordinateBounds)coordinateBounds; | ||
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| /** | ||
| The smallest coordinate rectangle that completely encompasses the circle. | ||
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| If the circle spans the antimeridian, its bounds may extend west of −180 | ||
| degrees longitude or east of 180 degrees longitude. For example, a circle | ||
| covering the Pacific Ocean from Tokyo to San Francisco might have a bounds | ||
| extending from (35.68476, −220.24257) to (37.78428, −122.41310). | ||
| */ | ||
| @property (nonatomic, readonly) MGLCoordinateBounds coordinateBounds; | ||
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| @end | ||
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| NS_ASSUME_NONNULL_END | ||
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| #import "MGLCircle.h" | ||
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| #import "MGLGeometry_Private.h" | ||
| #import "MGLMultiPoint_Private.h" | ||
| #import "NSCoder+MGLAdditions.h" | ||
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| #import <mbgl/util/projection.hpp> | ||
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| #import <vector> | ||
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| @implementation MGLCircle | ||
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| @synthesize coordinate = _coordinate; | ||
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| + (instancetype)circleWithCenterCoordinate:(CLLocationCoordinate2D)centerCoordinate radius:(CLLocationDistance)radius { | ||
| return [[self alloc] initWithCenterCoordinate:centerCoordinate radius:radius]; | ||
| } | ||
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| + (instancetype)circleWithCoordinateBounds:(MGLCoordinateBounds)coordinateBounds { | ||
| MGLCoordinateSpan span = MGLCoordinateBoundsGetCoordinateSpan(coordinateBounds); | ||
| BOOL latitudinal = span.latitudeDelta > span.longitudeDelta; | ||
| // TODO: Latitudinal distances aren’t uniform, so get the mean northing. | ||
| CLLocationCoordinate2D center = CLLocationCoordinate2DMake(coordinateBounds.ne.latitude - span.latitudeDelta / 2.0, | ||
| coordinateBounds.ne.longitude - span.longitudeDelta / 2.0); | ||
| CLLocationCoordinate2D southOrWest = CLLocationCoordinate2DMake(latitudinal ? coordinateBounds.sw.latitude : 0, | ||
| latitudinal ? 0 : coordinateBounds.sw.longitude); | ||
| CLLocationCoordinate2D northOrEast = CLLocationCoordinate2DMake(latitudinal ? coordinateBounds.ne.latitude : 0, | ||
| latitudinal ? 0 : coordinateBounds.ne.longitude); | ||
| CLLocationDistance majorAxis = MGLDistanceBetweenLocationCoordinates(southOrWest, northOrEast); | ||
| return [[self alloc] initWithCenterCoordinate:center radius:majorAxis / 2.0]; | ||
| } | ||
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| - (instancetype)initWithCenterCoordinate:(CLLocationCoordinate2D)centerCoordinate radius:(CLLocationDistance)radius { | ||
| if (self = [super init]) { | ||
| _coordinate = centerCoordinate; | ||
| _radius = radius; | ||
| } | ||
| return self; | ||
| } | ||
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| - (instancetype)initWithCoder:(NSCoder *)decoder { | ||
| if (self = [super initWithCoder:decoder]) { | ||
| _coordinate = [decoder decodeMGLCoordinateForKey:@"coordinate"]; | ||
| _radius = [decoder decodeDoubleForKey:@"radius"]; | ||
| } | ||
| return self; | ||
| } | ||
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| - (void)encodeWithCoder:(NSCoder *)coder { | ||
| [super encodeWithCoder:coder]; | ||
| [coder encodeMGLCoordinate:_coordinate forKey:@"coordinate"]; | ||
| [coder encodeDouble:_radius forKey:@"radius"]; | ||
| } | ||
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| - (BOOL)isEqual:(id)other { | ||
| if (other == self) { | ||
| return YES; | ||
| } | ||
| if (![other isKindOfClass:[MGLCircle class]]) { | ||
| return NO; | ||
| } | ||
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| MGLCircle *otherCircle = other; | ||
| return ([super isEqual:other] | ||
| && self.coordinate.latitude == otherCircle.coordinate.latitude | ||
| && self.coordinate.longitude == otherCircle.coordinate.longitude | ||
| && self.radius == otherCircle.radius); | ||
| } | ||
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| - (NSUInteger)hash { | ||
| return super.hash + @(self.coordinate.latitude).hash + @(self.coordinate.longitude).hash; | ||
| } | ||
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| - (NSUInteger)numberOfVertices { | ||
| // Due to the z16 zoom level and Douglas–Peucker tolerance specified by | ||
| // mbgl::ShapeAnnotationImpl::updateTileData() and GeoJSONVT, the smallest | ||
| // circle that can be displayed at z22 at the poles has a radius of about | ||
| // 5 centimeters and is simplified to four sides each about 0.31 meters | ||
| // (50 points) long. The smallest displayable circle at the Equator has a | ||
| // radius of about 5 decimeters and is simplified to four sides each about | ||
| // 3.1 meters (75 points) long. | ||
| constexpr NSUInteger maximumZoomLevel = 16; | ||
| CLLocationDistance maximumEdgeLength = mbgl::Projection::getMetersPerPixelAtLatitude(self.coordinate.latitude, maximumZoomLevel); | ||
| CLLocationDistance circumference = 2 * M_PI * self.radius; | ||
| NSUInteger maximumSides = ceil(fabs(circumference) / maximumEdgeLength); | ||
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| // The smallest perceptible angle is about 1 arcminute. | ||
| // https://en.wikipedia.org/wiki/Naked_eye#Small_objects_and_maps | ||
| constexpr CLLocationDirection maximumInternalAngle = 180.0 - 1.0 / 60; | ||
| constexpr CLLocationDirection maximumCentralAngle = 180.0 - maximumInternalAngle; | ||
| constexpr CGFloat maximumVertices = 360.0 / maximumCentralAngle; | ||
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| // Make the circle’s resolution high enough that the user can’t perceive any | ||
| // angles, but not so high that detail would be lost through simplification. | ||
| return ceil(MIN(maximumSides, maximumVertices)); | ||
| } | ||
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| - (mbgl::LinearRing<double>)linearRingWithNumberOfVertices:(NSUInteger)numberOfVertices { | ||
| CLLocationCoordinate2D center = self.coordinate; | ||
| CLLocationDistance radius = fabs(self.radius); | ||
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| mbgl::LinearRing<double> ring; | ||
| ring.reserve(numberOfVertices); | ||
| for (NSUInteger i = 0; i < numberOfVertices; i++) { | ||
| // Start at due north and go counterclockwise, or phase shift by 90° if | ||
| // centered in the southern hemisphere, so it’s easy to fix up for ±90° | ||
| // latitude in the conditional below. | ||
| CLLocationDirection direction = 360.0 / numberOfVertices * i + (center.latitude >= 0 ? 0 : 180); | ||
| CLLocationCoordinate2D vertex = MGLCoordinateAtDistanceFacingDirection(center, radius, direction); | ||
| // If the circle extends to ±90° latitude and has wrapped around, extend | ||
| // the polygon to include all of ±90° latitude and beyond. | ||
| if (i == 0 && radius > 1 | ||
| && fabs(vertex.latitude) < fabs(MGLCoordinateAtDistanceFacingDirection(center, radius - 1, direction).latitude)) { | ||
| short hemisphere = center.latitude >= 0 ? 1 : -1; | ||
| ring.push_back({ center.longitude - 180.0, vertex.latitude }); | ||
| ring.push_back({ center.longitude - 180.0, 90.0 * hemisphere }); | ||
| ring.push_back({ center.longitude + 180.0, 90.0 * hemisphere }); | ||
| } | ||
| ring.push_back(MGLPointFromLocationCoordinate2D(vertex)); | ||
| } | ||
| return ring; | ||
| } | ||
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| - (mbgl::Polygon<double>)polygon { | ||
| mbgl::Polygon<double> polygon; | ||
| polygon.push_back([self linearRingWithNumberOfVertices:self.numberOfVertices]); | ||
| return polygon; | ||
| } | ||
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| - (mbgl::Geometry<double>)geometryObject { | ||
| return [self polygon]; | ||
| } | ||
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| - (NSDictionary *)geoJSONDictionary { | ||
| return @{ | ||
| @"type": @"Polygon", | ||
| @"coordinates": self.geoJSONGeometry, | ||
| }; | ||
| } | ||
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| - (NSArray<id> *)geoJSONGeometry { | ||
| NSMutableArray *coordinates = [NSMutableArray array]; | ||
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| mbgl::LinearRing<double> ring = [self polygon][0]; | ||
| NSMutableArray *geoJSONRing = [NSMutableArray array]; | ||
| for (auto &point : ring) { | ||
| [geoJSONRing addObject:@[@(point.x), @(point.y)]]; | ||
| } | ||
| [coordinates addObject:geoJSONRing]; | ||
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| return [coordinates copy]; | ||
| } | ||
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| - (mbgl::Annotation)annotationObjectWithDelegate:(id <MGLMultiPointDelegate>)delegate { | ||
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| mbgl::FillAnnotation annotation { [self polygon] }; | ||
| annotation.opacity = { static_cast<float>([delegate alphaForShapeAnnotation:self]) }; | ||
| annotation.outlineColor = { [delegate strokeColorForShapeAnnotation:self] }; | ||
| annotation.color = { [delegate fillColorForShape:self] }; | ||
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| return annotation; | ||
| } | ||
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| - (MGLCoordinateBounds)coordinateBounds { | ||
| mbgl::LinearRing<double> ring = [self linearRingWithNumberOfVertices:4]; | ||
| CLLocationCoordinate2D southWest = CLLocationCoordinate2DMake(ring[2].y, ring[3].x); | ||
| CLLocationCoordinate2D northEast = CLLocationCoordinate2DMake(ring[0].y, ring[1].x); | ||
| return MGLCoordinateBoundsMake(southWest, northEast); | ||
| } | ||
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| - (NSString *)description { | ||
| return [NSString stringWithFormat:@"<%@: %p; coordinate = %@; radius = %f m>", | ||
| NSStringFromClass([self class]), (void *)self, | ||
| MGLStringFromCLLocationCoordinate2D(self.coordinate), self.radius]; | ||
| } | ||
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| @end |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,26 @@ | ||
| #import "MGLCircle.h" | ||
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| #import <mbgl/annotation/annotation.hpp> | ||
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| NS_ASSUME_NONNULL_BEGIN | ||
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| @protocol MGLMultiPointDelegate; | ||
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| @interface MGLCircle (Private) | ||
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| /** | ||
| The optimal number of vertices in the circle’s polygonal approximation. | ||
| */ | ||
| @property (nonatomic, readonly) NSUInteger numberOfVertices; | ||
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| /** | ||
| Returns a linear ring with the given number of vertices. | ||
| */ | ||
| - (mbgl::LinearRing<double>)linearRingWithNumberOfVertices:(NSUInteger)numberOfVertices; | ||
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| /** Constructs a circle annotation object, asking the delegate for style values. */ | ||
| - (mbgl::Annotation)annotationObjectWithDelegate:(id <MGLMultiPointDelegate>)delegate; | ||
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| @end | ||
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| NS_ASSUME_NONNULL_END |
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Do you think it is necessary to call out that this type does not support all the same paint/layout options as a shape added to an
MGLFillStyleLayer? I'm thinking specifically of fill patterns, but there are probably others as well.