Update SVGEngine.mm

[markm68k]

• pathDefinitionParser(svgString).parse() returns a CGMutablePathRef (which is a Core Foundation object). • The method parse() (see its implementation) creates this object by calling CGPathCreateMutable(), which returns a retained object according to Core Foundation memory management rules.

Thank you for submitting a PR for PocketSVG 😀

• If you're fixing an issue, please briefly describe the current behaviour and the new behaviour. If you're addressing an open issue, please link to it.

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[markm68k]

Addresses open issue #231

[arielelkin]

@codex

[arielelkin]

thanks for your patience! this has now been fixed via 1f5b96a

[markm68k]

@arielelkin I'm curious why you chose to use CF_RETURNS_RETAINED over renaming the function to CGPathCreateFromSVGPathString which would conform to Core Foundation memory management naming conventions.

[arielelkin]

good question @markm68k

a rename would introduce a source/ABI break for any consumer that already links against that symbol, and i ruled out pushing out a major version bump as i had just released 3.0.0.

adding the CF_RETURNS_RETAINED attribute conveys the same ownership conventions to Clang/ARC/Swift, so existing call sites keep compiling, and the compiler+analyzer still know the caller owns the returned CGPathRef.

[markm68k]

Of course, that makes sense. Thanks for the explanation, @arielelkin.