# MGLBackgroundStyleLayer

    @interface MGLBackgroundStyleLayer : MGLStyleLayer

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.

- `-initWithIdentifier:`

  Returns a background style layer initialized with an identifier.

  After initializing and configuring the style layer, add it to a map view’s style using the `-[MGLStyle addLayer:]` or `-[MGLStyle insertLayer:belowLayer:]` method.

  #### Declaration

  Objective-C

      - (nonnull instancetype)initWithIdentifier:(nonnull NSString *)identifier;

  Swift

      init(identifier: String)

  #### Parameters

  `identifier` | A string that uniquely identifies the source in the style to which it is added.

  View Source on GitHub

### Accessing the Paint Attributes

- `backgroundColor`

  The color with which the background will be drawn.

  The default value of this property is an expression that evaluates to `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.

  You can set this property to an expression containing any of the following:

  - Constant `UIColor` values
  - Predefined functions, including mathematical and string operators
  - Conditional expressions
  - Variable assignments and references to assigned variables
  - Interpolation and step functions applied to the `$zoomLevel` variable

  This property does not support applying interpolation or step functions to feature attributes.

  #### Declaration

  Objective-C

      @property (assign, readwrite, nonatomic, null_resettable)
          NSExpression *backgroundColor;

  Swift

      var backgroundColor: NSExpression! { get set }

  View Source on GitHub
- `backgroundColorTransition`

  The transition affecting any changes to this layer’s `backgroundColor` property.

  This property corresponds to the `background-color-transition` property in the style JSON file format.

  #### Declaration

  Objective-C

      @property (assign, readwrite, nonatomic) MGLTransition backgroundColorTransition;

  Swift

      var backgroundColorTransition: MGLTransition { get set }

  View Source on GitHub
- `backgroundOpacity`

  The opacity at which the background will be drawn.

  The default value of this property is an expression that evaluates to the float `1`. Set this property to `nil` to reset it to the default value.

  You can set this property to an expression containing any of the following:

  - Constant numeric values between 0 and 1 inclusive
  - Predefined functions, including mathematical and string operators
  - Conditional expressions
  - Variable assignments and references to assigned variables
  - Interpolation and step functions applied to the `$zoomLevel` variable

  This property does not support applying interpolation or step functions to feature attributes.

  #### Declaration

  Objective-C

      @property (assign, readwrite, nonatomic, null_resettable)
          NSExpression *backgroundOpacity;

  Swift

      var backgroundOpacity: NSExpression! { get set }

  View Source on GitHub
- `backgroundOpacityTransition`

  The transition affecting any changes to this layer’s `backgroundOpacity` property.

  This property corresponds to the `background-opacity-transition` property in the style JSON file format.

  #### Declaration

  Objective-C

      @property (assign, readwrite, nonatomic)
          MGLTransition backgroundOpacityTransition;

  Swift

      var backgroundOpacityTransition: MGLTransition { get set }

  View Source on GitHub
- `backgroundPattern`

  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).

  You can set this property to an expression containing any of the following:

  - Constant string values
  - Predefined functions, including mathematical and string operators
  - Conditional expressions
  - Variable assignments and references to assigned variables
  - Step functions applied to the `$zoomLevel` variable

  This property does not support applying interpolation functions to the `$zoomLevel` variable or applying interpolation or step functions to feature attributes.

  #### Declaration

  Objective-C

      @property (assign, readwrite, nonatomic, null_resettable)
          NSExpression *backgroundPattern;

  Swift

      var backgroundPattern: NSExpression! { get set }

  View Source on GitHub
- `backgroundPatternTransition`

  The transition affecting any changes to this layer’s `backgroundPattern` property.

  This property corresponds to the `background-pattern-transition` property in the style JSON file format.

  #### Declaration

  Objective-C

      @property (assign, readwrite, nonatomic)
          MGLTransition backgroundPatternTransition;

  Swift

      var backgroundPatternTransition: MGLTransition { get set }

  View Source on GitHub