[ios, macos] Update and reformat documentation for runtime styling (#7475)

* [ios, macos] Optimized changelog for runtime styling

Changelog entries related to style JSON now lead off with the analogous portion of the runtime styling API.

* [ios, macos] Autolink cross-class property references in docs

jazzy can autolink `Class.property` references in documentation comments.

* [ios, macos] Removed extra blank lines

* [ios, macos] Corrected typo in MGLMultiPoint docs

* [ios, macos] Rewrote shape and feature docs

Rewrote documentation about MGLShape, its subclasses, and MGLFeature to emphasize runtime styling uses over annotation uses, associate each type with real-world concepts, cross-reference related style layer classes, and cross-reference related or easily confused shape classes. Links to the GeoJSON specification have been updated to RFC 7946.

* [ios, macos] Expanded style layer docs

With this change, documentation about style layer classes is nominally based on the documentation in the style specification. However, all the existing layer types’ documentation has been overridden to explain what the layer looks like, relate the layer to a real-world concept, and cross-reference related geometry classes. This change also corrects the description of MGLBackgroundStyleLayer, which erroneously stated that the identifier must be “background”, whereas that only happens to be true by default for Studio template styles.

* [ios, macos] Wrap style layer docs

* [ios, macos] Removed unused code

* [ios, macos] Corrected symbol references in docs

* [ios, macos] Corrected typo in abstract class exception

1 files changed, 30 insertions, 12 deletions

diff --git a/platform/darwin/src/MGLBackgroundStyleLayer.h b/platform/darwin/src/MGLBackgroundStyleLayer.h
index 656e104bbb..bcaf21a8d4 100644
--- a/platform/darwin/src/MGLBackgroundStyleLayer.h
+++ b/platform/darwin/src/MGLBackgroundStyleLayer.h
@@ -7,10 +7,18 @@
 NS_ASSUME_NONNULL_BEGIN
 
 /**
- A map style's background layer is the bottommost layer and is used to style a color 
- or pattern to show below all other map features. You can query an `MGLMapView` for its 
- `style` and obtain the background layer using the `-[MGLStyle layerWithIdentifier:]` 
- method and passing `background` for the identifier. 
+ An `MGLBackgroundStyleLayer` is a style layer that covers the entire map. Use a
+ background style layer to configure a color or pattern to show below all other
+ map content. If the style’s other layers use the Mapbox Streets source, the
+ background style layer is responsible for drawing land, whereas the oceans and
+ other bodies of water are drawn by `MGLFillStyleLayer` objects.
+ 
+ A background style layer is typically the bottommost layer in a style, because
+ it covers the entire map and can occlude any layers below it. You can therefore
+ access it by getting the last item in the `MGLStyle.layers` array.
+ 
+ If the background style layer is transparent or omitted from the style, any
+ portion of the map view that does not show another style layer is transparent.
  */
 @interface MGLBackgroundStyleLayer : MGLStyleLayer
 
@@ -22,18 +30,24 @@ NS_ASSUME_NONNULL_BEGIN
 /**
  The color with which the background will be drawn.
  
- The default value of this property is an `MGLStyleValue` object containing `UIColor.blackColor`. Set this property to `nil` to reset it to the default value.
-
- This property is only applied to the style if `backgroundPattern` is set to `nil`. Otherwise, it is ignored.
+ The default value of this property is an `MGLStyleValue` object containing
+ `UIColor.blackColor`. Set this property to `nil` to reset it to the default
+ value.
+ 
+ This property is only applied to the style if `backgroundPattern` is set to
+ `nil`. Otherwise, it is ignored.
  */
 @property (nonatomic, null_resettable) MGLStyleValue<MGLColor *> *backgroundColor;
 #else
 /**
  The color with which the background will be drawn.
  
- The default value of this property is an `MGLStyleValue` object containing `NSColor.blackColor`. Set this property to `nil` to reset it to the default value.
-
- This property is only applied to the style if `backgroundPattern` is set to `nil`. Otherwise, it is ignored.
+ The default value of this property is an `MGLStyleValue` object containing
+ `NSColor.blackColor`. Set this property to `nil` to reset it to the default
+ value.
+ 
+ This property is only applied to the style if `backgroundPattern` is set to
+ `nil`. Otherwise, it is ignored.
  */
 @property (nonatomic, null_resettable) MGLStyleValue<MGLColor *> *backgroundColor;
 #endif
@@ -41,12 +55,16 @@ NS_ASSUME_NONNULL_BEGIN
 /**
  The opacity at which the background will be drawn.
  
- The default value of this property is an `MGLStyleValue` object containing an `NSNumber` object containing the float `1`. Set this property to `nil` to reset it to the default value.
+ The default value of this property is an `MGLStyleValue` object containing an
+ `NSNumber` object containing the float `1`. Set this property to `nil` to reset
+ it to the default value.
  */
 @property (nonatomic, null_resettable) MGLStyleValue<NSNumber *> *backgroundOpacity;
 
 /**
- Name of image in style images to use for drawing an image background. For seamless patterns, image width and height must be a factor of two (2, 4, 8, ..., 512).
+ Name of image in style images to use for drawing an image background. For
+ seamless patterns, image width and height must be a factor of two (2, 4, 8,
+ ..., 512).
  */
 @property (nonatomic, null_resettable) MGLStyleValue<NSString *> *backgroundPattern;