What XCode and MacOS/iOS versions to support

[MikeGitb]

As the title says: What is the policy (if any) for supported OS and development versions in the applec eco system?

For Windows and Linux the decision was to require VS2019 and Ubuntu18.04 respectively, but I'm not aware about any decision towards XCode. Background is that I created a PR to update travis to accomodate for the increased CMake requirements (#2199), but short of deactivating the failing XCode tests, I didn't know what to do there. I could of course install a newer cmake in the CI script, but if supporting those versions won't be a goal for cinder 9.3, then I'd prefer to safe the hassel (just using brew update cmake causes a long increase in runtime because it will also first build several dependencies of cmake from source).

I have never used or developed for Mac or iOS, so I'm completely blind here. From what I read on wikipedia and a few blogs, my impression is that Apple itself supports a new MacOS Version for about 3 years and XCode is generally only supported on the OS it was released for. Is that correct?
So, if I'm understanding this correctly, the oldest OS version supported by apple is high sierra (MacOS 10.13) and the corresponding XCode version is 9.3/9.4. Would that be a reasonable minimum requirement? Btw. travis uses XCode 9.4 as a default (https://docs.travis-ci.com/user/reference/osx/).

[totalgee]

My personal opinion: as a sometimes-macOS Cinder user, I would be happy if Xcode 9.4 continued to be supported by Cinder (I'm still using macOS 10.13 which requires the Xcode 9 "family"), and would be sadder if it required a newer Xcode (v10, 11 or 12). However, I expect I'll likely move to Xcode 10 within the next year. Since Xcode 9.4 was released in spring 2018, I guess I fit into that three-year window you describe... (-;