[ios, macos] fixes #6160: allow updating multipoint coordinates

platform/darwin/src/MGLMultiPoint.h

@@ -35,6 +35,16 @@ NS_ASSUME_NONNULL_BEGIN
  */
 - (void)getCoordinates:(CLLocationCoordinate2D *)coords range:(NSRange)range;
 
+/**
+ Updates the coordinates for the shape, which will instantaneously redraw the 
+ shape if it is currently visible on the map. 
+ 
+ @param coords The array of coordinates defining the shape. The data in this
+ array is copied to the object.
+ @param count The number of items in the `coords` array.
+ */
+- (void)updateCoordinates:(CLLocationCoordinate2D *)coords count:(NSUInteger)count;
+
 @end
 
 NS_ASSUME_NONNULL_END

platform/darwin/src/MGLMultiPoint.mm

@@ -25,21 +25,28 @@ - (instancetype)initWithCoordinates:(CLLocationCoordinate2D *)coords
 
     if (self)
     {
-        _count = count;
-        _coordinates = (CLLocationCoordinate2D *)malloc(_count * sizeof(CLLocationCoordinate2D));
+        [self setupWithCoordinates:coords count:count];
+    }
+
+    return self;
+}
+
+- (void)setupWithCoordinates:(CLLocationCoordinate2D *)coords count:(NSUInteger)count
+{
+    if (_coordinates) free(_coordinates);
 
-        mbgl::LatLngBounds bounds = mbgl::LatLngBounds::empty();
+    _count = count;
+    _coordinates = (CLLocationCoordinate2D *)malloc(_count * sizeof(CLLocationCoordinate2D));
 
-        for (NSUInteger i = 0; i < _count; i++)
-        {
-            _coordinates[i] = coords[i];
-            bounds.extend(mbgl::LatLng(coords[i].latitude, coords[i].longitude));
-        }
+    mbgl::LatLngBounds bounds = mbgl::LatLngBounds::empty();
 
-        _bounds = MGLCoordinateBoundsFromLatLngBounds(bounds);
+    for (NSUInteger i = 0; i < _count; i++)
+    {
+        _coordinates[i] = coords[i];
+        bounds.extend(mbgl::LatLng(coords[i].latitude, coords[i].longitude));
     }
 
-    return self;
+    _bounds = MGLCoordinateBoundsFromLatLngBounds(bounds);
 }
 
 - (void)dealloc
@@ -93,6 +100,22 @@ - (void)getCoordinates:(CLLocationCoordinate2D *)coords range:(NSRange)range
     }
 }
 
+- (void)updateCoordinates:(CLLocationCoordinate2D *)coords count:(NSUInteger)count
+{
+    if ([self isMemberOfClass:[MGLMultiPoint class]])
+    {
+        [[NSException exceptionWithName:@"MGLAbstractClassException"
+                                 reason:@"MGLMultiPoint is an abstract class"
+                               userInfo:nil] raise];
+    }
+
+    assert(_count > 0);
+
+    [self willChangeValueForKey:@"coordinates"];
+    [self setupWithCoordinates:coords count:count];
+    [self didChangeValueForKey:@"coordinates"];
+}
+
 - (MGLCoordinateBounds)overlayBounds
 {
     return _bounds;

platform/ios/src/MGLMapView.mm

@@ -1795,6 +1795,29 @@ - (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(N
             }
         }
     }
+    else if ([keyPath isEqualToString:@"coordinates"] && [object isKindOfClass:[MGLMultiPoint class]])
+    {
+        MGLMultiPoint *annotation = object;
+        MGLAnnotationTag annotationTag = (MGLAnnotationTag)(NSUInteger)context;
+        // We can get here because a subclass registered itself as an observer
+        // of the coordinates key path of a multipoint annotation but failed
+        // to handle the change. This check deters us from treating the
+        // subclass’s context as an annotation tag. If the context happens to
+        // match a valid annotation tag, the annotation will be unnecessarily
+        // but safely updated.
+        if (annotation == [self annotationWithTag:annotationTag])
+        {
+            // Update the annotation’s backing geometry to match the annotation model object.
+            _mbglMap->updateAnnotation(annotationTag, [annotation annotationObjectWithDelegate:self]);
+
+            // We don't current support shape multipoint annotation selection, but let's make sure
+            // deselection is handled just to avoid problems in the future.
+            if (annotationTag == _selectedAnnotationTag)
+            {
+                [self deselectAnnotation:annotation animated:YES];
+            }
+        }
+    }
 }
 
 + (NS_SET_OF(NSString *) *)keyPathsForValuesAffectingZoomEnabled
@@ -2840,6 +2863,8 @@ - (void)addAnnotations:(NS_ARRAY_OF(id <MGLAnnotation>) *)annotations
             MGLAnnotationContext context;
             context.annotation = annotation;
             _annotationContextsByAnnotationTag[annotationTag] = context;
+
+            [(NSObject *)annotation addObserver:self forKeyPath:@"coordinates" options:0 context:(void *)(NSUInteger)annotationTag];
         }
         else if ( ! [annotation isKindOfClass:[MGLMultiPolyline class]]
                  || ![annotation isKindOfClass:[MGLMultiPolygon class]]
@@ -3132,6 +3157,10 @@ - (void)removeAnnotations:(NS_ARRAY_OF(id <MGLAnnotation>) *)annotations
         {
             [(NSObject *)annotation removeObserver:self forKeyPath:@"coordinate" context:(void *)(NSUInteger)annotationTag];
         }
+        else if ([annotation isKindOfClass:[MGLMultiPoint class]])
+        {
+            [(NSObject *)annotation removeObserver:self forKeyPath:@"coordinates" context:(void *)(NSUInteger)annotationTag];
+        }
 
         _mbglMap->removeAnnotation(annotationTag);
     }