Djinni CMake 🧞‍♂️

Simple CMake wrapper for Djinni.

Motivation

While I like to have a good portion of configuration options in the Djinni Generator, I think it is easier to get started with Djinni if a few presumptions are made for the developer.

This wrapper attempts to be a tool that allows a quick and simple start into a new project with C++ using Djinni.

It may evolve over time to a more powerful utility with more configuration options. This depends on your feedback and my future requirements.

Features

• 🎯 Easy to use
• 🧶 Little configuration required
• 🧩 Convention over configuration
• 🎳 Supports targets Java (Android), Objective-C (macOS, iOS, ...) and C# (Windows .NET 5 & .NET Framework)

Prerequisites

• CMake >= 3.19
• Djinni Generator >= 1.1.0

Installation

Copy the file Djinni.cmake from the latest release to your CMake modules folder and include it in the root CMakeLists.txt:

set(CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/cmake/modules ${CMAKE_MODULE_PATH})
include(Djinni)

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Synopsis

add_djinni_library(<target> [SHARED|STATIC]
        IDL <filename>
        LANGUAGES <CPP|JAVA|CPPCLI|OBJC> [CPP|JAVA|CPPCLI|OBJC ...]
        [NO_JNI_MAIN]
        [NO_OBJC_PREFIX]
        [NO_DSYM]
        [NAMESPACE <namespace>]
        [DIRECTORY <output-dir>]
        [SOURCES <sources>]
        [JAR_OUTPUT_DIR <jar-output-dir>]
)

Calls Djinni Generator and creates a target with name <target> from the generated sources. The YAML definition of the generated interface is available on the targets include directory.

If generating for Java, additionally a target <target>-java is created, that builds a jar named <target>.jar with the Java gluecode to <jar-output-dir> when the target <target> is built.

This generator is intentionally favoring convention over configuration to keep things as simple as possible. If you miss a configuration option anyways, please consider opening an issue.

Options

The options are:

• IDL <filename>
  filename/path of the Djinni-IDL file that should be processed

• SHARED|STATIC
  Optional;
  Type of library. If no type is given explicitly the type is STATIC or SHARED based on whether the current value of the variable BUILD_SHARED_LIBS is ON.

• LANGUAGES
  list of languages that bindings should be generated for. Possible values: CPP, JAVA, CPPCLI, OBJC

• NO_JNI_MAIN
  Optional;
  By default JNI_OnLoad & JNI_OnUnload entrypoints for JNI are included. Set this argument to not include entrypoints.

• NO_OBJC_PREFIX
  Optional;
  By default Objective-C Types are prefixed with a few letters derived from the provided NAMESPACE. This option disables the prefix.

• NO_DSYM
  Optional;
  When targeting Objective-C, by default the XCode property DEBUG_INFORMATION_FORMAT is set to dwarf-with-dsym, which will generate a .dSYM directory containing debugging symbols. This option disables the dSYM generation.

• NAMESPACE <namespace>
  Optional; Default: Djinni
  The namespace for the generated code. Each namespace part should start with an uppercase letter. The namespace is used for the generated C++ code, but also automatically transformed to a Java package & ObjC prefix.
  Examples:

  NAMESPACE value	C++ namespace	Java package	ObjC prefix
  Djinni::Lib	Djinni::Lib	djinni.lib	DL
  My::LibExample	My::LibExample	my.libexample	MLE

• DIRECTORY <output-dir>
  Optional; Default: djinni-generated
  The output directory where the generated code should be written to.

• SOURCES <sources>
  Optional;
  Additional sources. This could for example be the sources that implement the Djinni interface in C++.

• JAR_OUTPUT_DIR <jar-output-dir>
  Optional; Default: ${CMAKE_CURRENT_BINARY_DIR}
  The directory to which the jar should be written if gluecode for Android is created.

Example

For a full usage example please have a look at jothepro/djinni-library-template!

Given a Djinni-IDL file named example.djinni, this is all you need in your CMakeLists.txt:

add_djinni_library(Example
    IDL example.djinni
    LANGUAGES CPP JAVA CPPCLI OBJC
    NAMESPACE Demo
    SOURCES
      src/example.cpp
)

This will generate a target Example that contains all the required gluecode from the interface defined in example.djinni and it's implementation source src/example.cpp.

All C++ classes will be in the namespace Demo, all Java classes in the package demo and all ObjC structures will have the prefix D.

All generated header files can be found on the include path under Demo/

If the target language is Java, a jar named Example.jar will be built to ${CMAKE_CURRENT_BINARY_DIR} once the target Example is built.

If the target language is Objective-C, a Swift Bridging Header can be found on the include path: Demo/Example.h

Troubleshooting

• The Djinni executable can not be found! 😠
  Solution: Explicitly define the full path of the djinni binary in DJINNI_EXECUTABLE.

Credits

Thanks to the work of @freitass (Djinni.cmake) and @a4z (djinni_process_idl.cmake) for inspiring me to write this wrapper.