Add iOS build support

[axmo]

This adds support for running on (and cross-compiling to) iOS devices, as described in #643 (comment)

See ios/README.md for build instructions.

[crudelios]

Thanks for this!

Here are my small suggestions.

[crudelios]

I'm also thinking: instead of adding the sources to ios/SDL2, can't we use the existing ext/SDL2?

That way the directory convention would be consistent in all builds.

[axmo]

I'm also thinking: instead of adding the sources to ios/SDL2, can't we use the existing ext/SDL2?

That way the directory convention would be consistent in all builds.

We could! For iOS I'm building SDL and mixer from source, and I wasn't sure if the other platforms using ext/SDL2 were expecting the source or binary releases there, which is why I put it under ios/SDL2. (Where are other platforms finding SDL2_mixer?)

[crudelios]

What we usually do is use ext/SDL2/SDL2-2.X.X and ext/SDL2/SDL2_mixer-2.X.X.

Things get a bit messy if you're trying to configure for different platforms from the same base directory, but with some effort it works and, more importantly, it works just fine for github actions.

Speaking of which, the test build is failing. I think it's an include in julius.c which should be inside some#ifdefs but isn't. Can you check please?

Also: do you think you can add a github actions workflow to automate ios builds? If not, can you at least provide command line instructions here for building the app so we later create the workflow ourselves?

Thanks!

[axmo]

Ok. for iOS I'm adding the SDL2 and SDL2_mixer CMake projects with add_subdirectory, as suggested in this libSDL forum post, so I'll use ext/SDL2/SDL2/... and ext/SDL2/SDL2_mixer/...

Automated iOS builds for distribution would require putting a signing certificate and provisioning profile on GitHub, which I'm not prepared to do myself, but if you just want to check that it builds correctly, or run tests in a simulator I guess that's doable. A warning: GitHub actions running on macOS cost 10x the price of GitHub actions on Linux, and in my experience builds on GitHub take ages. (that was a few years ago, maybe it has gotten better?)

[crudelios]

Yeah for now we just want to check that it builds.

The macOS action is free, our mac build is done using it. I think we use a self signing certificate.

[axmo]

Ignore previous stuff about the ext/SDL/... location, I've taken a look at /.ci_scripts/ and am adding an install_sdl_ios, which will follow the same directory structure as the others.

[axmo]

Hm. Debug builds for simulator and for device work, but creating a release archive (used for App Store or Ad-Hoc distribution) causes an error:

Wrong SDL_config.h, check your include path?, which seems to be because USING_GENERATED_CONFIG_H is set, but I'm not sure why it would only be set for release builds.

I thought I had everything working, but apparently I was using old build artifacts. Clean builds currently fail when building SDL2. Error: Wrong SDL_config.h, check your include path?, which seems to be because USING_GENERATED_CONFIG_H is set, but I'm not sure WHY it is set.

[crudelios]

Did you try deleting the SDL2 folder (and adding it brand new) and all intermediate build caches on your PC?

Android studio also has a lot of problems rebuilding, and deleting everything to start fully clean usually fixes them.

[axmo]

Aha. looks like I had multiple copies of SDL2 and SDL2_mixer in ext/SDL2 after running install_dependencies, which were all being copied to build/ext and then due to header search path precedence, it was loading the wrong SDL_config.h as a result.

All seems to be working now, and I've added the necessary run_cmake and run_build scripts

[axmo]

Please let me know if anything else is needed for this to be considered ready to merge.

[bvschaik]

Looking good in general 👍 I mainly have some small questions due to not being familiar with the inner workings of iOS.

[crudelios]

The Visual Studio build is failing with this error:

D:\a\julius\julius\src\platform\ios\ios.h(4,1): error C2773: #import and #using available only in C++ compiler [D:\a\julius\julius\build\julius.vcxproj]
  (compiling source file '../src/platform/julius.c')

Maybe only include ios.h from julius.c if the target build is iOS? It's not ideal, but if that's the only way to prevent the issue, then so be it.

Or, instead of #import, is it possible to use #include?

[axmo]

Or, instead of #import, is it possible to use #include?

Ah, yes, it should indeed be #include (and now it is)

[axmo]

Once again ready for consideration.

[crudelios]

Ah nice, the builds are working on all platforms now.

Thinking a bit ahead, you're still planning to add support for augustus, right?

In that case, is it okay if, when this is merged to Julius, I then merge the latest Julius changes to augustus and you work from there?

[bvschaik]

Looks good to me, let's merge 👍