Default to system font in attribution titles

[1ec5]

The inline stylesheet used when converting an attribution HTML string to an attributed string now specifies the system font as the default font. It still isn’t clear to me why macosapp has been defaulting to the system font, but it makes sense to me that the default default font would be Times without this change. This change makes use of WebKit’s proprietary -apple-system keyword, which Apple recommends for this purpose.

There is still a slight difference between macosapp and an application outside macos.xcworkspace, but I think the two results are close enough:

Fixes #7722.

/cc @frederoni @friedbunny

[1ec5]

This issue is tagged as a release blocker because it’s a highly visible regression on macOS compared to v0.2.1. It is not a release blocker on iOS, as it affects iOS only to the extent that a developer would try to display an MGLAttributionInfo title as rich text. The attribution sheet is unaffected because it displays each title as plain text. Even so, I’d like to land this change in time for macOS SDK v0.3.0, which means it’ll be in iOS SDK v3.4.0 as well.

[friedbunny]

The WebKit blog says -apple-system is supported from OS X 10.11 (and iOS 9, incidentally). We support back to 10.10, so I think it’d make sense to also add "Helvetica Neue" to this rule, the previous system font.

The only question I would then have is if OS X 10.10 still used Helvetica Neue at small sizes...

[1ec5]

The only question I would then have is if OS X 10.10 still used Helvetica Neue at small sizes...

Yes, Lucida Grande was supplanted by Helvetica Neue at all three control sizes.

[1ec5]

Support for the -apple-system keyword was introduced in WebKit/WebKit@a03afe2 for bug 144707, which made it into iOS 9 and OS X 10.11. But the same functionality was actually available earlier via the identical -apple-system-font keyword, upstreamed from iOS in WebKit/WebKit@b8ade58 for bug 126654 (which would’ve made it into iOS 8) and introduced to OS X in WebKit/WebKit@989ba14 for bug 133382 (which made it into Safari 538.1 and thus OS X 10.10). Therefore I’ve added -apple-system-font as a fallback. I also added sans-serif to at least ensure something reasonably close to Helvetica Neue on iOS 7.

Additionally, on macOS, I set font: -webkit-mini-control to apply a font identical to what macosapp displays:

[friedbunny]

@1ec5 You’re absolutely correct — the blog piece I cited doesn’t actually say when -apple-system became available, just that you could use San Francisco via that keyword in OS X 10.11 and iOS 9. 🙇