Add support for using Yoga from swift on non Darwin platforms.

[iainsmith]

Specify that enums are closed for correct swift export on non darwin platforms.

Related Yoga Issue

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Swift exports plain c enums as constants. On Darwin the yoga macros hit the NS_ENUM case which generates a swift enum, however on linux NS_ENUM is not defined.

See [This post] for a some more background. https://belkadan.com/blog/2021/10/Swift-Regret-Unannotated-C-Enums/

Tested on a couple of CI builds:

• Failing build
• Passing build swift build passes on this, but swift test is failing still for unrelated reasons.

Which results in a compiler error for the missing switch cases.

[303/309] Compiling YogaSwift YGNodeView.swift
/home/runner/work/YogaSwift/YogaSwift/Sources/YogaSwift/YGNode.swift:50:56: error: type 'YGDirection' has no member 'LTR'
48 |     width: Float = YGValueUndefined.value, height: Float = YGValueUndefined.value
49 |   ) {
50 |     YGNodeCalculateLayout(self.__node, width, height, .LTR)
   |                                                        `- error: type 'YGDirection' has no member 'LTR'
51 |   }
52 | }

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[NickGerleman]

This breaks the build on non-Clang platforms.

[NickGerleman]

A couple of these are flag enums, which would also need to be declared I think

[iainsmith]

@NickGerleman Are the only bitmask flags YGErrata & YGExperimentalFeature or are there others?

[iainsmith]

Just realised that enums.py specifies that only Errata is a bitset enum.

How do you feel about us adding a YG_ENUM_FLAG_DECL macro, and then updating enums.py to check BITSET_ENUMS to decide on which macro to use?

[NickGerleman]

That sounds good to me!

[iainsmith]

@NickGerleman , I took a quick stab at this on this branch, but I've run into a compiler error I'm not sure how to approach.

~/Developer/personal/yoga/yoga/../yoga/YGEnums.h:61:5: 
error: enumeration value 'YGErrataClassic' is out of range of flags in enumeration type 'YGErrata' [-Werror,-Wflag-enum]
   61 |     YGErrataClassic = 2147483646,
      |     ^
~/Developer/personal/yoga/yoga/../yoga/YGEnums.h:62:5: 
error: enumeration value 'YGErrataAll' is out of range of flags in enumeration type 'YGErrata' [-Werror,-Wflag-enum]
   62 |     YGErrataAll = 2147483647)

Do you have thoughts on the best way to handle that?

[iainsmith]

This breaks the build on non-Clang platforms.

Makes sense. I'll push a change to wrap this in a clang check.

---

Should be fixed now. Quickly tested with
cmake -DCMAKE_C_COMPILER=/usr/bin/gcc -DCMAKE_CXX_COMPILER=/usr/bin/g++ && make

note to self. /usr/bin/gcc on mac is a wrapper around clang.