How far back to the non-deprecated symbols exist? With 3.3 (see #18066 and #17956 ) we accidentally put a floor on the version of OSX to support.

What is below is a brain dump.

I think that OSX SDK version should fall under the "system and C-dependencies" category of https://matplotlib.org/devel/min_dep_policy.html so we should should support "as old as practical". We should define what "practical" means in this case (as per #18066 ).

Given discussion in macports/macports-ports@b07e0eb it seems at least some people are advocating for a pattern of building on new OSX but being able to run on older OSX (which fits with how we do the wheels), but leaves people who a) have very old macs b) want to build from source them selves in a bind.

The built Python on python.org reportedly supports back to 10.9 (I suspect because they are not using much of the SDK surface particularly around GUI work the way we do), macports also tries to support back very far (but that is their jam).

Right, the new symbols probably don't exist in 10.11.

It looks like Travis can run builds in OSX 10.11 so once the minimum version is decided, perhaps we should test the build in that version: https://docs.travis-ci.com/user/reference/osx/#macos-version

I think that second commit is the way to stay compatible, but I can't actually properly test myself. I recently had to upgrade my remaining 10.13 system, because various pieces of software were dropping support.

Unfortunately, due to @available I don't think we'll build on anything earlier than the xcode9 image, which is macOS 10.12. Might be worth giving that a shot here and seeing where we are.

👍 to the changes.

Converting to draft until I can figure out the CI build

Unfortunately, due to @available I don't think we'll build on anything earlier than the xcode9 image, which is macOS 10.12. Might be worth giving that a shot here and seeing where we are.

Given that macports is happy (for now) to patch us and are considering moving to build on newer systems to target older systems this seems like a good place to draw the line.

Thanks @jkseppan !

This does not build wheels when targeting 10.9: https://github.com/matplotlib/matplotlib/actions/runs/221342241

I thought we weren't ourselves supporting building on 10.9?

Hmm, well the MacPython wheels still specify 10.9, but maybe we determined that that had no effect? And now cibuildwheel is correctly passing that along?

I'm very confused by this though. The PR is doing

#define CGContext                            graphicsPort

but the error we get is:

  src/_macosx.m:1661:59: error: 'CGContext' is only available on macOS 10.10 or newer [-Werror,-Wunguarded-availability]
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      CGContextRef cr = [[NSGraphicsContext currentContext] CGContext];
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                                                            ^~~~~~~~~~
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  /Applications/Xcode_11.6.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/System/Library/Frameworks/AppKit.framework/Headers/NSGraphicsContext.h:81:35: note: 'CGContext' has been marked as being introduced in macOS 10.10 here, but the deployment target is macOS 10.9.0
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  @property (readonly) CGContextRef CGContext NS_RETURNS_INNER_POINTER API_AVAILABLE(macos(10.10));
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which makes me worry I don't understand what #define does in objective-c....

or at least the order in which the version checking vs marco expansion happens...

So what do we want to do about this? Target a newer macOS version? It also breaks building on the shared Mac mini.

I think we should make a decision about the minimum version of macOS that we support (#18066). Based on this comment by @tacaswell I would suggest making that 10.12:

Unfortunately, due to @available I don't think we'll build on anything earlier than the xcode9 image, which is macOS 10.12. Might be worth giving that a shot here and seeing where we are.

Given that macports is happy (for now) to patch us and are considering moving to build on newer systems to target older systems this seems like a good place to draw the line.

Whichever way that's decided, we can build wheels targeting the supported version and up, and fix the build as needed.