Using haxe as a transpiler between c++ and JavaScript

Question

Firstly I apologise for the long post. I have been asking a few questions about haxe and its suitability as a tool to solve a problem I am facing. I have very limited knowledge of haxe but what I do know is my ideal role for haxe in my project is not the normal use of haxe. So what I'm trying to avoid is wasting time I don't have learning this language (despite it looking really fun and powerful) only to find that it isn't fit for purpose. So I am hoping to get some advice from you haxe seasoned vets on whether it is fit for purpose. I truly hope that it is.

Here is what I am trying to achieve:

I work in the games industry and I need to create a game in both C++ and JS. C++ for an embedded system and JS for online and mobile. I am very experienced in both C++ and JS.

The games I develop I only want to write the once. Now I could use something like emscripten for going from C++ to JS but this will result in compiled JS code that cant be debugged with chrome dev tools easily. I'm converned that I will run into edge case bugs with the compiled JS that I cant easily tace back to the original C++. Plus some platforms for the game would require fairness laboratories to view the source code which would be an issue for compiled JS.

What I really need is a source to source compiler that produces native and human readable c++ and JS code that I can then work with and modify in its native form if necessary, hence haxe. I've looked at the code produced by haxe for C++ and JS. JS looks perfectly easy to understand and work with. C++ not so much but still just about acceptable. I can even stop haxe from compiling and linking C++ which I dont need. I only want the source code.

So far so good.

Now I have a game framework in c++ that uses oxygine 2d engine. It is capable of showing sprites etc as well as a framework I have created for message buses and finite state machines (loads more useful classes too). I also have a similar framework in JS which uses Pixijs for its 2d engine and has its own message bus etc just like the C++ engine.

Now what I want to be able to do is write modules in haxe that when I transpile to both C++ and JS that the code can be included as part of the framework and work with its respected language engine. Each object I create in haxe will be very encapsulated and will just need to subscribe to the message bus, handle messages and send messages back. It may also need to know how to use its engines state machine. So I have no idea if this is even possible with haxe as the message bus (along with other objects) will not be written in haxe but will be supplied to the module after it has been transpiled and built in its native project. Maybe I can write my own haxe library that knows the syntax for my two game engines and can transpile depending on its target language? Not sure it that is possible.

Thanks for taking the time to read, and any advice you can give.

Answer 1

You can use

#if cpp
// c++ implementation
#elseif js
// javascript implementation
#end

to allow some different implementations for different targets, this can go anywhere in your code, so you can pass a Haxe value to different functions for different targets.

To use extern definitions:

• http://haxe.org/manual/lf-externs.html
• http://old.haxe.org/doc/js/extern_libraries

With c++ specifically it might be more complex you need to look at CFFI or Linc https://snowkit.github.io/linc/
The complexity is probably getting the types across. Remember Haxe c++ has managed memory your engine might do things differently. Also HL is coming soon and may have some advantages.

Looking at oxygine2d it seems a bit like the Flash API? And I know pixijs is based roughly off the Flash API. I believe that OpenFL now uses pixijs for WebGL rendering. You might want to also look at NME ( has nearly same interface for C++ as OpenFL, but NME has stuff like Cppia setup and is sometimes more stable ). If the JS or C++ is too slow you need to look into shaders and Luxe/Kha for render and you might want to also try Heaps it uses Lime ( openfl ) and some haxe js webgl I think.
If you need 2D physics then use Nape it can be used with any of the Haxe toolkits (Luxe, OpenFL, Kha, Flambe), there is physaxe but that's not used as much. Kha and Nape info eg: https://github.com/lewislepton/kha-examples/blob/master/NAPE/Sources/Project.hx

I really suspect that your making your life hard by wanting to use different engines for different platforms when probably HaxeFlixel or Punk could give you all you need running with Nape on one of the cross target toolkits, but it's very feasible to do it your way.

Maybe look at Tink or Thx for signals event buses and the like, macros (like used in Tink) allow a lot of structures to be built at compile and so can reduce much of the overhead by doing it before run-time, so tweens can be pre-calculated by the compiler. There is a hxcpp debugger and if you run Haxe in chrome it should give you the Haxe line number via js source mapping.

Hopefully I have covered some aspects of your large question.

Haxe allows you to mix and match with native, but I think to use Pixijs and oxygine 2d is probably not ideal as there is bound to be enough good game tools in pure Haxe with target optimizations built in, you just need to go onto Kha IRC, Luxe gitter, and Haxe IRC and OpenFL forum and ask a few questions.