Information for Style Authors

A style defines a map view’s content and appearance. If you’ve authored a style using Mapbox Studio’s Styles editor or as JSON in a text editor, you can use that style in this SDK and manipulate it afterwards in code. This document provides information you can use to ensure a seamless transition from Mapbox Studio to your application.

Designing for macOS

When designing your style, consider the context in which your application shows the style. There are a number of considerations specific to macOS that may not be obvious when designing your style in Mapbox Studio on the Web. A map view is essentially a graphical user interface element, so many of same issues in user interface design also apply when designing a map style.


Ensure sufficient contrast in your application’s user interface when your map style is present. Standard user interface elements such as toolbars, sidebars, and sheets often overlap the map view with a translucent, blurred background, so make sure the contents of these elements remain legible with the map view underneath. If you intend your style to be used in the dark, consider the impact that Night Shift may have on your style’s colors.

Typography and graphics

Design sprite images and choose font weights that look crisp on both standard-resolution displays and Retina displays. This SDK supports the same resolutions as macOS. Standard-resolution displays are often found on external monitors. Even with built-in screens, some of your users may use the Larger Text option in Display Preferences, which is essentially standard resolution, to make text easier to read.

Icon and text labels should be legible regardless of the map’s orientation. By default, this SDK makes it easy for your users to rotate or tilt the map using multitouch trackpad gestures or keyboard shortcuts. If you do not intend your design to accommodate rotation and tilting, disable these gestures using the MGLMapView.rotateEnabled and MGLMapView.pitchEnabled properties, respectively, or the corresponding inspectables in Interface Builder.


Pay attention to whether elements of your style appear to be interactive. An icon with a shadow or shading effect may appear to be clickable. You can make an icon or text label interactive by installing a gesture recognizer and performing feature querying (e.g., -[MGLMapView visibleFeaturesAtPoint:]) to get details about the selected feature. You can install cursor or tooltip tracking rectangles to indicate interactive features as an alternative to prominent hover effects.

Make sure your users can easily distinguish any interactive elements from the surrounding map, such as pins or a route line. If your application supports printing, consider using the runtime styling API to optimize your style for ink economy before printing the map view.

For more information about user interface design, consult Apple’s macOS Human Interface Guidelines.

Applying your style

You set an MGLMapView object’s style either in code, by setting the MGLMapView.styleURL property, or in Interface Builder, by setting the “Style URL” inspectable. The URL must point to a local or remote style JSON file. The style JSON file format is defined by the GL Style Specification. This SDK supports the functionality defined by version 8 of the specification unless otherwise noted in the style specification documentation.

Manipulating the style at runtime

The runtime styling API enables you to modify every aspect of a style dynamically as a user interacts with your application. The style itself is represented at runtime by an MGLStyle object, which provides access to various MGLSource and MGLStyleLayer objects that represent content sources and style layers, respectively.

The names of runtime styling classes and properties on macOS are generally consistent with the style specification and Mapbox Studio’s Styles editor. Any exceptions are listed in this document.

To avoid conflicts with Objective-C keywords or Cocoa terminology, this SDK uses the following terms for concepts defined in the style specification:

In the style specification In the SDK
class style class
filter predicate
function type interpolation mode
id identifier
image style image
layer style layer
property attribute
SDF icon template image
source content source

Specifying the map’s content

Each source defined by a style JSON file is represented at runtime by a content source object that you can use to initialize new style layers. The content source object is a member of one of the following subclasses of MGLSource:

In style JSON In the SDK
geojson MGLShapeSource
raster MGLRasterSource
vector MGLVectorSource

Tile sources

Raster and vector sources may be defined in TileJSON configuration files. This SDK supports the properties defined in the style specification, which are a subset of the keys defined in version 2.1.0 of the TileJSON specification. As an alternative to authoring a custom TileJSON file, you may supply various tile source options when creating a raster or vector source. These options are detailed in the MGLTileSourceOption documentation:

In style JSON In TileJSON In the SDK
url configurationURL parameter in -[MGLTileSource initWithIdentifier:configurationURL:]
tiles tiles tileURLTemplates parameter in -[MGLTileSource initWithIdentifier:tileURLTemplates:options:]
minzoom minzoom MGLTileSourceOptionMinimumZoomLevel
maxzoom maxzoom MGLTileSourceOptionMaximumZoomLevel
tileSize MGLTileSourceOptionTileSize
attribution attribution MGLTileSourceOptionAttributionHTMLString (but consider specifying MGLTileSourceOptionAttributionInfos instead for improved security)
scheme scheme MGLTileSourceOptionTileCoordinateSystem

Shape sources

Shape sources also accept various options. These options are detailed in the MGLShapeSourceOption documentation:

In style JSON In the SDK
data url parameter in -[MGLShapeSource initWithIdentifier:URL:options:]
maxzoom MGLShapeSourceOptionMaximumZoomLevel
buffer MGLShapeSourceOptionBuffer
tolerance MGLShapeSourceOptionSimplificationTolerance
cluster MGLShapeSourceOptionClustered
clusterRadius MGLShapeSourceOptionClusterRadius
clusterMaxZoom MGLShapeSourceOptionMaximumZoomLevelForClustering

To create a shape source from local GeoJSON data, first convert the GeoJSON data into a shape, then use the -[MGLShapeSource initWithIdentifier:shape:options:] method.

Configuring the map content’s appearance

Each layer defined by the style JSON file is represented at runtime by a style layer object, which you can use to refine the map’s appearance. The style layer object is a member of one of the following subclasses of MGLStyleLayer:

In style JSON In the SDK
background MGLBackgroundStyleLayer
circle MGLCircleStyleLayer
fill MGLFillStyleLayer
line MGLLineStyleLayer
raster MGLRasterStyleLayer
symbol MGLSymbolStyleLayer

You configure layout and paint attributes by setting properties on these style layer objects. The property names generally correspond to the style JSON properties, except for the use of camelCase instead of kebab-case. Properties whose names differ from the style specification are listed below:

Circle style layers

In style JSON In Objective-C In Swift
circle-pitch-scale MGLCircleStyleLayer.circleScaleAlignment MGLCircleStyleLayer.circleScaleAlignment
circle-translate MGLCircleStyleLayer.circleTranslation MGLCircleStyleLayer.circleTranslation
circle-translate-anchor MGLCircleStyleLayer.circleTranslationAnchor MGLCircleStyleLayer.circleTranslationAnchor

Fill style layers

In style JSON In Objective-C In Swift
fill-antialias MGLFillStyleLayer.fillAntialiased MGLFillStyleLayer.isFillAntialiased
fill-translate MGLFillStyleLayer.fillTranslation MGLFillStyleLayer.fillTranslation
fill-translate-anchor MGLFillStyleLayer.fillTranslationAnchor MGLFillStyleLayer.fillTranslationAnchor

Line style layers

In style JSON In Objective-C In Swift
line-dasharray MGLLineStyleLayer.lineDashPattern MGLLineStyleLayer.lineDashPattern
line-translate MGLLineStyleLayer.lineTranslation MGLLineStyleLayer.lineTranslation
line-translate-anchor MGLLineStyleLayer.lineTranslationAnchor MGLLineStyleLayer.lineTranslationAnchor

Raster style layers

In style JSON In Objective-C In Swift
raster-brightness-max MGLRasterStyleLayer.maximumRasterBrightness MGLRasterStyleLayer.maximumRasterBrightness
raster-brightness-min MGLRasterStyleLayer.minimumRasterBrightness MGLRasterStyleLayer.minimumRasterBrightness
raster-hue-rotate MGLRasterStyleLayer.rasterHueRotation MGLRasterStyleLayer.rasterHueRotation

Symbol style layers

In style JSON In Objective-C In Swift
icon-allow-overlap MGLSymbolStyleLayer.iconAllowsOverlap MGLSymbolStyleLayer.iconAllowsOverlap
icon-ignore-placement MGLSymbolStyleLayer.iconIgnoresPlacement MGLSymbolStyleLayer.iconIgnoresPlacement
icon-image MGLSymbolStyleLayer.iconImageName MGLSymbolStyleLayer.iconImageName
icon-optional MGLSymbolStyleLayer.iconOptional MGLSymbolStyleLayer.isIconOptional
icon-rotate MGLSymbolStyleLayer.iconRotation MGLSymbolStyleLayer.iconRotation
icon-size MGLSymbolStyleLayer.iconScale MGLSymbolStyleLayer.iconScale
icon-keep-upright MGLSymbolStyleLayer.keepsIconUpright MGLSymbolStyleLayer.keepsIconUpright
text-keep-upright MGLSymbolStyleLayer.keepsTextUpright MGLSymbolStyleLayer.keepsTextUpright
text-max-angle MGLSymbolStyleLayer.maximumTextAngle MGLSymbolStyleLayer.maximumTextAngle
text-max-width MGLSymbolStyleLayer.maximumTextWidth MGLSymbolStyleLayer.maximumTextWidth
symbol-avoid-edges MGLSymbolStyleLayer.symbolAvoidsEdges MGLSymbolStyleLayer.symbolAvoidsEdges
text-field MGLSymbolStyleLayer.text MGLSymbolStyleLayer.text
text-allow-overlap MGLSymbolStyleLayer.textAllowsOverlap MGLSymbolStyleLayer.textAllowsOverlap
text-font MGLSymbolStyleLayer.textFontNames MGLSymbolStyleLayer.textFontNames
text-size MGLSymbolStyleLayer.textFontSize MGLSymbolStyleLayer.textFontSize
text-ignore-placement MGLSymbolStyleLayer.textIgnoresPlacement MGLSymbolStyleLayer.textIgnoresPlacement
text-justify MGLSymbolStyleLayer.textJustification MGLSymbolStyleLayer.textJustification
text-optional MGLSymbolStyleLayer.textOptional MGLSymbolStyleLayer.isTextOptional
text-rotate MGLSymbolStyleLayer.textRotation MGLSymbolStyleLayer.textRotation
icon-translate MGLSymbolStyleLayer.iconTranslation MGLSymbolStyleLayer.iconTranslation
icon-translate-anchor MGLSymbolStyleLayer.iconTranslationAnchor MGLSymbolStyleLayer.iconTranslationAnchor
text-translate MGLSymbolStyleLayer.textTranslation MGLSymbolStyleLayer.textTranslation
text-translate-anchor MGLSymbolStyleLayer.textTranslationAnchor MGLSymbolStyleLayer.textTranslationAnchor

Setting attribute values

Each property representing a layout or paint attribute is set to an MGLStyleValue object, which is either an MGLConstantStyleValue object (for constant values) or an MGLStyleFunction object (for style functions). The style value object is a container for the raw value or function parameters that you want the attribute to be set to.

Constant style values

In contrast to the JSON type that the style specification defines for each layout or paint property, the style value object often contains a more specific Foundation or Cocoa type. General rules for attribute types are listed below. Pay close attention to the SDK documentation for the attribute you want to get or set.

In style JSON In Objective-C In Swift
Color NSColor NSColor
Enum NSValue (see NSValue(MGLAdditions)) NSValue (see NSValue(MGLAdditions))
String NSString String
Boolean NSNumber.boolValue Bool
Number NSNumber.floatValue Float
Array (-dasharray) NSArray<NSNumber> [Float]
Array (-font) NSArray<NSString> [String]
Array (-offset, -translate) NSValue containing CGVector NSValue containing CGVector
Array (-padding) NSValue.edgeInsetsValue NSValue.edgeInsetsValue

For padding attributes, note that the arguments to NSEdgeInsetsMake() in Objective-C and EdgeInsets(top:left:bottom:right:) in Swift are specified in counterclockwise order, in contrast to the clockwise order defined by the style specification.

Additionally, on macOS, a screen coordinate of (0, 0) is located at the lower-left corner of the screen. Therefore, a positive CGVector.dy means an offset or translation upward, while a negative CGVector.dy means an offset or translation downward. This is the reverse of how CGVector is interpreted on iOS.

Style functions

A style function allows you to vary the value of a layout or paint attribute based on the zoom level, data provided by content sources, or both. For more information about style functions, see “Using Style Functions at Runtime”.

Each kind of style function is represented by a distinct class, but you typically create style functions as you create any other style value, using class methods on MGLStyleValue:

In style specification SDK class SDK factory method
zoom function MGLCameraStyleFunction +[MGLStyleValue valueWithInterpolationMode:cameraStops:options:]
property function MGLSourceStyleFunction +[MGLStyleValue valueWithInterpolationMode:sourceStops:attributeName:options:]
zoom-and-property function MGLCompositeStyleFunction +[MGLStyleValue valueWithInterpolationMode:compositeStops:attributeName:options:]

The documentation for each individual style layer property indicates the kinds of style functions that are enabled for that property.

When you create a style function, you specify an interpolation mode and a series of stops. Each stop determines the effective value displayed at a particular zoom level (for camera functions) or the effective value on features with a particular attribute value in the content source (for source functions). The interpolation mode tells the SDK how to calculate the effective value between any two stops:

In style specification In the SDK
exponential MGLInterpolationModeExponential
interval MGLInterpolationModeInterval
categorical MGLInterpolationModeCategorical
identity MGLInterpolationModeIdentity

Filtering sources

You can filter a shape or vector source by setting the MGLVectorStyleLayer.predicate property to an NSPredicate object. Below is a table of style JSON operators and the corresponding operators used in the predicate format string:

In style JSON In the format string
["has", key] key != nil
["!has", key] key == nil
["==", key, value] key == value
["!=", key, value] key != value
[">", key, value] key > value
[">=", key, value] key >= value
["<", key, value] key < value
["<=", key, value] key <= value
["in", key, v0, …, vn] key IN {v0, …, vn}
["!in", key, v0, …, vn] NOT key IN {v0, …, vn}
["all", f0, …, fn] p0 AND … AND pn
["any", f0, …, fn] p0 OR … OR pn
["none", f0, …, fn] NOT (p0 OR … OR pn)

See the MGLVectorStyleLayer.predicate documentation for a full description of the supported operators and operand types.


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