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Contributing to the Mapbox Maps SDK for iOS

This document explains how to build the Mapbox Maps SDK for iOS from source. It is intended for advanced developers who wish to contribute to Mapbox GL and the Mapbox Maps SDK for iOS.

Requirements

See the "Requirements" section in INSTALL.md.

Building the SDK

Create and open an Xcode workspace that includes both the SDK source and some Objective-C test applications by running:

make iproj

Xcode schemes

Before building, use the scheme picker button in the toolbar to change the scheme to iosapp and the destination to one of the simulators or connected devices listed in the menu.

iosapp is only one of several shared schemes. Others include:

  • CI builds exactly what gets built for continuous integration on Bitrise.
  • bench is a simple benchmarking application. For more consistent results between runs, run platform/ios/benchmark/assets/{glyphs,tiles}/download.sh to download any necessary resources.
  • dynamic builds the SDK as a dynamic framework.
  • static builds the SDK as a static library and separate resource bundle.
  • dynamic+static is a combination of the dynamic and static schemes.

If you don’t have an Apple Developer account, change the destination to a simulator such as “iPhone 6s” before you build and run the app.

Packaging builds

Install jazzy for generating API documentation:

[sudo] gem install jazzy

Build and package the SDK by using one of the following commands:

  • make ipackage builds both dynamic and static frameworks in the Debug configuration for devices and the iOS Simulator.
  • make iframework builds a dynamic framework in the Debug configuration for devices and the iOS Simulator. The CocoaPods pod downloads the output of this target.
  • make ipackage-sim builds a dynamic framework in the Debug configuration for the iOS simulator. This is the fastest target.
  • make ipackage-strip builds both dynamic and static frameworks in the Debug configuration, stripped of debug symbols, for devices and the iOS Simulator.

You can customize the build output by passing the following arguments into the make invocation:

  • BUILDTYPE=Release will optimize for distribution. Defaults to Debug.
  • BUILD_DEVICE=false builds only for the iOS Simulator.
  • FORMAT=dynamic builds only a dynamic framework. FORMAT=static builds only a static framework, for legacy compatibility.
  • SYMBOLS=NO strips the build output of any debug symbols, yielding smaller binaries. Defaults to YES.

An example command that creates a dynamic framework suitable for eventual App Store distribution:

make iframework BUILDTYPE=Release

The products of these build commands can be found in the build/ios/pkg folder at the base of the repository.

Contributing

Making any symbol public

To add any Objective-C type, constant, or member to the iOS SDK’s public interface:

  1. Ensure that the symbol is pure Objective-C and does not rely on any language features specific to Objective-C++ or the C11 dialect of C – so no namespaced types or classes named with emoji! 🙃 Most projects that depend on this SDK are either written in pure Objective-C (GNU99 dialect) or Swift, which cannot yet bridge C++ types.
  2. Name the symbol according to Cocoa naming conventions. Use the MGL class prefix to avoid conflicts with client code. If the symbol has an analogue in MapKit, name the symbol according to MapKit.
  3. Provide full documentation comments. We use jazzy to produce the documentation found in the SDK distribution and on the website for this SDK. We also recognize that many developers rely on Xcode’s Quick Help feature. jazzy supports Markdown formatting; however, Quick Help supports only HeaderDoc syntax and a subset of Doxygen syntax. For hyperlinks, use HTML syntax, which is recognized by both tools.

Making a type or constant public

To add an Objective-C class, protocol, category, typedef, enumeration, or global constant to the iOS maps SDK’s public interface:

  1. (Optional.) Add the macro MGL_EXPORT prior to the declaration for classes and global constants when adding them in shared headers located in platform/darwin. To use this macro, include MGLFoundation.h. You can check whether all public symbols are exported correctly by running make check-public-symbols.
  2. (Optional.) Add the type or constant’s name to the relevant category in the custom_categories section of the jazzy configuration file. This is required for classes and protocols and also recommended for any other type that is strongly associated with a particular class or protocol. If you leave out this step, the symbol will appear in an “Other” section in the generated HTML documentation’s table of contents.
  3. (Optional.) If the symbol would also be publicly exposed in the macOS maps SDK, consult the companion macOS document for further instructions.

Adding a source code file

To add an Objective-C header or implementation file to the iOS maps SDK:

  1. Add the file to the Headers or Compile Sources build phase, as appropriate, of both the “dynamic” and “static” targets. You can either use the Build Phases tab of the project editor or the Target Membership section of the File inspector.
  2. Audit new headers for nullability. Typically, you will wrap a header with NS_ASSUME_NONNULL_BEGIN and NS_ASSUME_NONNULL_END.
  3. (Optional.) If it’s a public header, change its visibility from Project to Public and import it in the iOS SDK’s umbrella header.
  4. (Optional.) If the file would also be used by the macOS maps SDK, make sure it’s in platform/darwin/src/, then consult the companion macOS document for further instructions.

Adding a resource

To add a resource (such as an image, SSL certificate, property list, or strings table) to the iOS maps SDK:

  1. Add the header to the Copy Bundle Resources build phase of both the “dynamic” and “bundle” targets. You can either use the Build Phases tab of the project editor or the Target Membership section of the File inspector.
  2. (Optional.) If the resource would also be used by the macOS maps SDK, make sure it’s in platform/darwin/resources/, then consult the companion macOS document for further instructions.

Adding user-facing text

To add or update text that the user may see in the iOS maps SDK:

  1. Make sure the implementation file imports NSBundle+MGLAdditions.h.
  2. Use the NSLocalizedStringWithDefaultValue() macro:
  • key is a unique identifier that won’t change if the user-facing text ever needs to change.
  • tbl is Foundation in code shared between the iOS and macOS maps SDKs, or nil otherwise.
  • bundle is nil; the redefined macro looks for the SDK bundle at runtime and ignores this argument.
  • val is the English string.
  1. (Optional.) When dealing with a number followed by a pluralized word, do not split the string. Instead, use a format string and make val ambiguous, like %d file(s). Then pluralize for English in the appropriate .stringsdict file. See platform/darwin/resources/en.lproj/Foundation.stringsdict for an example. Localizers should do likewise for their languages.
  2. Run make genstrings and commit any changes it makes to .strings files. The make rule also updates the macOS maps SDK’s strings tables.

Adding a localization

Translations of all the Mapbox GL Native SDKs are managed in Transifex. If your language already has a translation, feel free to complete or proofread it. Otherwise, please request your language. Note that we’re primarily interested in languages that iOS supports as system languages.

Once you’ve finished translating the SDK into a new language in Transifex, perform these steps to make Xcode aware of the translation:

  1. In ios.xcworkspace, open the project editor for ios.xcodeproj. Using the project editor’s sidebar or tab bar dropdown, go to the “ios” project; under the Localizations section of the Info tab, click the + button to add your language to the project.
  2. In the sheet that appears, select all the .strings and .stringsdict files but not the .storyboard file. (LaunchScreen.storyboard is part of the iosapp example application, which is not localized.) If your language lacks declension and pluralization, as in the case of Chinese, omit the .stringsdict files.
  3. In the Project navigator, expand each .stringsdict file in the project. An additional version for your localization should be listed; translate it. See Apple’s documentation on the .stringsdict format.
  4. In the Project navigator, select Demo App/Localizable.strings and then, in the File Inspector, check the box for your new localization.
  5. Repeat the steps above in macos.xcworkspace.

The .strings files should still be in the original English – that’s expected. Now you can pull your translations into this repository:

  1. (First time only.) Download the tx command line tool and configure your .transifexrc.
  2. Run tx pull -a.
  3. Convert any added .strings files from UTF-16 encoding to UTF-8 encoding to facilitate diffing and merging. You can convert the file encoding using Xcode’s File inspector or the following command (substituting MYLANG for the locale code):
find platform/{darwin,ios}/resources platform/macos/sdk -path '*/MYLANG.lproj/*.strings' -exec textutil -convert txt -extension strings -inputencoding UTF-16 -encoding UTF-8 {} -output {} \;

Adding a code example

To add an example code listing to the documentation for a class or class member:

  1. Add a test method named in the form testMGLClass or testMGLClass$method to MGLDocumentationExampleTests. Wrap the code you’d like to appear in the documentation within //#-example-code and //#-end-example-code comments.
  2. If the header doesn’t already have an example code listing, add the path to the header to platform/darwin/scripts/update-examples.list.
  3. Insert the code listings into the headers:
make darwin-update-examples

SourceKitten is required and will be installed automatically using Homebrew.

Testing

make ios-test builds and runs unit tests of cross-platform code as well as the SDK.

To instead run the cross-platform tests in Xcode instead of on the command line:

  1. Run make iproj to set up the workspace.
  2. Change the scheme to “test (platform project)” and press Command-R to run core unit tests.
  3. Change the scheme to “CI” and press Command-U to run SDK integration tests.

Access tokens

The included applications use Mapbox vector tiles, which require a Mapbox account and API access token. Obtain an access token on the Mapbox account page. You will be prompted for this access token the first time you launch the demo or benchmarking application. In the iOS Simulator, you can paste your access token by pressing Command-V, holding down the left mouse button in the text field, and pressing the Paste button that appears.

Using iosapp

  • Pan to move
  • Pinch to zoom
  • Use two fingers to rotate
  • Double-tap to zoom in one level
  • Two-finger single-tap to zoom out one level
  • Double-tap, long-pressing the second, then pan up and down to "quick zoom" (meant for one-handed use)
  • Use the debug menu to add test annotations, reset position, and cycle through the debug options.